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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of
the Securities Exchange Act of 1934 (Amendment No.          )

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IRON MOUNTAIN INCORPORATED
NOTICE OF 20162018 ANNUAL MEETING OF STOCKHOLDERS
TO BE HELD ON JUNE 17, 2016
14, 2018

To the Stockholders of
IRON MOUNTAIN INCORPORATED:

        Iron Mountain Incorporated will hold its 20162018 Annual Meeting of Stockholders, or the Annual Meeting, at the offices of Sullivan & Worcester LLP, One Post Office Square, 21st Floor, Boston, Massachusetts 02109, on June 17, 2016,14, 2018, at 10:9:00 a.m. local timeU.S. Eastern Time (11:00 p.m. Australian Eastern Standard Time on June 14, 2018) for the following purposes:

1.

To elect twelve (12)eleven (11) directors to the Board of Directors of Iron Mountain Incorporated for a one-year term as directors or until their successors are elected and qualified;



2.

To hold a non-binding, advisory vote on the compensation of Iron Mountain Incorporated's Named Executive Officers as described in the accompanying Proxy Statement;



3.

To ratify the selection by the Audit Committee of Deloitte & Touche LLP as Iron Mountain Incorporated's independent registered public accounting firm for the year ending December 31, 2016;2018; and



4.

To transact such other business as may properly come before the Annual Meeting.

        Attached to this notice is a Proxy Statement relating to the proposals to be considered at the Annual Meeting. The Board of Directors of Iron Mountain Incorporated has fixed the close of business on April 20, 201617, 2018 (5:00 p.m. U.S. Eastern Time) as the record date, or the Record Date, for the determination of stockholders entitled to receive notice of and to vote at the Annual Meeting or at any adjournment or postponement thereof. This Proxy Statement is datedRecord holders of CHESS Depositary Interests, or CDIs, as of 5:00 p.m. U.S. Eastern Time on the Record Date (7:00 a.m. Australian Eastern Standard Time on April 26, 2016.18, 2018) are entitled to receive notice of and attend the Annual Meeting or any adjournment or postponement thereof but may not vote in person at the Annual Meeting.

        United States Securities and Exchange Commission rules allow us to furnish proxy materials to our stockholders on the internet. YouStockholders can now access proxy materials and vote at www.proxyvote.com. YouStockholders may also vote via internet or telephone by following the instructions on that website. In order to vote on the internet or by telephone, youstockholders must have a stockholder identification number, which is being mailed to youstockholders of record on a Notice Regarding the Availability of Proxy Materials.

        CDI holders may vote the shares of our common stock underlying their CDIs through our CDI Depositary, CHESS Depositary Nominees Pty Ltd, or CDN. Each CDI holder may instruct CDN to vote on behalf of such CDI holder at the Annual Meeting by either following the instructions on the CDI voting instruction form, which is being mailed to CDI holders of record, or by voting online at www.linkmarketservices.com.au. CDI holders may instruct CDN to vote on their behalf only by completing and signing the CDI voting instruction form or voting online at www.linkmarketservices.com.au.

        YOUR VOTE IS IMPORTANT REGARDLESS OF THE NUMBER OF SHARES THAT YOU BENEFICIALLY OWN.    We urge you to read the Proxy Statement carefully and, whether or not you plan to attend the Annual Meeting, to castvote your shares (or direct CDN to vote if you hold your shares in the form of CDIs) without delay online, by telephone (if you are a stockholder) or by mailing a completed proxy card (if you are a stockholder and you elect to receive the proxy materials by mail) or CDI voting instruction form. Instructions regarding each method of voting are provided on the proxy card and the CDI voting instruction form. If you desire to submit your vote without delay as instructed in the Notice Regarding the Availability of Proxy Materials thatby mail, you receive in the mail. You may also request a paper proxy card or a replacement CDI voting instruction form at any time on or before June 3, 2016 to submit your vote by mail. Proxies may be revoked, or the votes reflected in the proxy changed, by (1) delivering written notice or another duly executed proxy bearing a later date to the Secretary of Iron Mountain Incorporated, (2) completing another proxy in the same manner indicated on the website referred to in the Notice Regarding the Availability of Proxy Materials or (3) attending the Annual Meeting and voting in person.1, 2018. If you hold shares in the name of a brokerage firm, bank, nominee or other institution, you must provide a legal proxy from that institution in order to vote your shares at the Annual Meeting, except as otherwise discussed in the Proxy Statement.

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        All stockholders and CDI holders are cordially invited to attend the Annual Meeting.

Boston, Massachusetts
April 30, 2018

        IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE 2018 ANNUAL MEETING OF STOCKHOLDERS TO BE HELD ON JUNE 17, 2016:STOCKHOLDERS: This Notice of Annual Meeting and Proxy Statement, Iron Mountain Incorporated's Annual Report to Stockholders for the year ended December 31, 20152017 and directions to the Annual Meeting are available at: www.materials.proxyvote.com/https://materials.proxyvote.com/46284v. If you are a CDI holder, you may also view and print these materials online at www.linkmarketservices.com.au.

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IRON MOUNTAIN INCORPORATED
PROXY STATEMENT
FOR THE 20162018 ANNUAL MEETING OF STOCKHOLDERS

To be held on June 17, 201614, 2018

GENERAL INFORMATION

        This Proxy Statement is furnished in connection with the solicitation of proxies by the Board of Directors, or the Board, of        Iron Mountain Incorporated, or Iron Mountain, the Company, we, us or our, is furnishing this Proxy Statement in connection with the solicitation of proxies by the Iron Mountain Board of Directors, or the Board, for use at the Company's Annual Meeting of Stockholders to be held at 9:00 a.m. U.S. Eastern Time on June 17, 2016,14, 2018 (11:00 p.m. Australian Eastern Standard Time on June 14, 2018), or the Annual Meeting, or at any adjournment or postponement thereof. All stockholders and holders of CHESS Depositary Interests, or CDIs, of record on April 20, 201617, 2018 (5:00 p.m. U.S. Eastern Time), or the Record Date, are invited to attend the Annual Meeting. The Company's Annual Report to Stockholders for the year ended December 31, 20152017 and the Notice Regarding the Availability of Proxy Materials relating to the Annual Meeting, or the Notice of Internet Availability, is first being mailed from the United States to stockholders of the CompanyCompany's stockholders on or about April 26, 2016.30, 2018, and the CDI voting instruction form is first being mailed from Australia to CDI holders on or about May 1, 2018 (which is the next business day in Australia following the day of mailing in the United States).

        The Company will bear all costs of solicitation of proxies. Brokers, banks, custodians and other fiduciaries will be requested to forward proxy solicitation materials to the beneficial owners of shares held of record by such persons, and the Company will reimburse thembrokers, banks, custodians and other fiduciaries for their reasonable out-of-pocket expenses incurred in connection with the distribution of such proxy solicitation materials. Solicitation of proxies by mail may be supplemented by telephone, telecopier or personal solicitation by directors, officers or other regular employees of the Company (who will not receive any additional compensation for any solicitation of proxies).

        The Board unanimously recommends that you vote:

•

FOR the election of each of the Board's nominees for director;



•

FOR the approval of a non-binding, advisory resolution approving the compensation of the Named Executive Officers as described in this Proxy Statement; and



•

FOR the ratification of the selection by the Audit Committee of Deloitte & Touche LLP as the Company's independent registered public accounting firm for the year ending December 31, 2016.2018.

Stockholders and CDI Holders Entitled to Vote

        Iron Mountain's common stock, $0.01 par value per share, or the Common Stock, is the only class of voting securities outstanding and entitled to vote at the Annual Meeting. Shares of Common Stock also trade on the Australian Stock Exchange, or ASX, in the form of CDIs. Each CDI represents a beneficial interest in one share of Common Stock. As of the close of business5:00 p.m. U.S. Eastern Time on April 20, 2016, the record date for the determination of stockholders entitled to notice of and to vote at the Annual Meeting, or the Record Date, 211,946,343285,923,944 shares of Common Stock (including 9,117,764 CDIs exchangeable into shares of Common Stock) were outstanding and entitled to vote. Each share of Common Stock is entitled to one vote on each matter.

How to Vote

        Your vote is very important no matter how many shares of Common Stock or CDIs you own. Whether or not you plan to attend the Annual Meeting, we urge you to vote your shares of Common Stock or CDIs today.

        If youStockholders who wish to receive a paper or email copy of the proxy card to complete and mail to the Company in time for the Annual Meeting you may request one at any time on or before June 3, 2016. You1, 2018.

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Stockholders may vote yourtheir shares over the internet or by telephone in the manner provided on the website indicated in the Notice of Internet Availability youthey receive in the mail, or the Website, by completing and returning a proxy card or by attending the Annual Meeting and voting in person. CDI holders may instruct our CDI Depositary, CHESS Depositary Nominees Pty Ltd, or CDN, to vote on their behalf only by completing and signing the CDI voting instruction form they receive in the mail or voting online at www.linkmarketservices.com.au. Votes provided over the internet or by telephone by stockholders must be received by 11:59 p.m. U.S. Eastern Daylight Time on June 16, 2016.13, 2018, and instructions provided over the internet by our CDI holders must be received by 1:59 p.m. Australian Eastern Standard Time on June 11, 2018.

If You Are a Registered Holder of Common Stock

        If you are a registered holder of Common Stock, you may vote your shares of Common Stock, or Shares, either by voting by proxy in advance of the Annual Meeting or by voting in person at the Annual Meeting. By submitting a proxy (on a proxy card or in the manner provided on the Website), you are legally authorizing another person to vote your sharesShares on your behalf. We urge you to vote (1) FOR the Board's nominees for director, (2) FOR the approval of a non-binding, advisory resolution approving the compensation of our Named Executive Officers as described in this Proxy Statement and (3) FOR the ratification of the selection by the Audit Committee of Deloitte & Touche LLP as the Company's independent registered public accounting firm for the year ending December 31, 2016. If you submit your executed proxy card or submit a proxy in the manner provided on the Website, your sharesShares will be voted in accordance with the Board's recommendations set forth in this Proxy Statement, unless otherwise directed, in which case your sharesShares will be voted as specified by you on the proxy. In addition, if any other matters are brought before the Annual Meeting (other than the proposals contained in this Proxy Statement), then the individuals listed on the proxy will have the authority to vote your sharesShares on those other matters in accordance with their discretion and judgment.

        In case a quorum is not present at the Annual Meeting, the holders of a majority of the voting power of the sharesShares present at the Annual Meeting in person or represented by proxy may adjourn the Annual Meeting (without notice other than announcement of adjournment at the Annual Meeting) to another time, or to another time and place.

        Whether or not you plan to attend the Annual Meeting, we urge you to promptly vote over the internet or by telephone in the manner provided on the Website or by completing and returning a proxy card. If you later decide to attend the Annual Meeting and vote in person, the vote you cast in person at the Annual Meeting will automatically revoke any previously submitted proxy.

If You Hold Your Shares of Common Stock "In Street Name"

        If your sharesShares are held in the name of a brokerage firm, bank, nominee or other institution (referred to as "in street name"), you will receive instructions from the holder of record, or street name holder, that you must follow in order for you to specify how your sharesShares will be voted. If you do not specify how you would like your sharesShares to be voted, your sharesShares held in street name may still be voted. Certain street name holders have the authority to vote sharesShares for which their customers do not provide voting instructions on certain routine, uncontested items.proposals. The election of directors and the advisory vote on executive compensation are not routine matters for purposes of broker voting. The ratification of the selection of our independent registered public accounting firm for the fiscal year ending December 31, 20162018 is a routine matter; therefore, there will be no broker non-votes in connection with that matter.

        IMPORTANT: If your sharesShares are held in the name of a brokerage firm, bank, nominee or other institution, you should provide instructions to your broker, bank, nominee or other institution on how to vote your shares.Shares. Please contact the person responsible for your account and give instructions for a proxy to be completed for your shares.Shares.

If You Hold CDIs

        Each CDI holder is entitled to direct CDN to cast one vote for each CDI held by such holder. CDI holders are entitled to receive notice of and attend the Annual Meeting and any adjournment or

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postponement thereof and may direct CDN to vote their underlying shares of Common Stock at the Annual Meeting by (1) returning a validly completed CDI voting instruction form to Link Market Services Limited, Locked Bag A14, Sydney South, New South Wales, Australia 1235, the agent we designated for the collection and processing of voting instructions from our CDI holders, so that it is received by no later than 1:59 p.m. Australian Eastern Standard Time on June 11, 2018 (which is 11:59 p.m. U.S. Eastern Time on June 10, 2018) or (2) voting online at www.linkmarketservices.com.au before 1:59 p.m. Australian Eastern Standard Time on June 11, 2018 (which is 11:59 p.m. U.S. Eastern Time on June 10, 2018).

        Alternatively, any CDI holder may inform the Company that such CDI holder wishes to nominate himself or another person to be appointed as CDN's proxy with respect to such CDI holder's underlying Shares for the purposes of attending and voting at the Annual Meeting. Holders of CDIs will not appear on the Company's share register as the legal holders of Common Stock; therefore, no CDI holder will be entitled to vote at the Annual Meeting unless such CDI holder is appointed as a proxy by CDN.

Quorum

        The presence at the Annual Meeting, in person or by proxy, of stockholders entitled to cast at least a majority of the votes that all stockholders are entitled to cast at the Annual Meeting, including the Shares represented by the CDIs, will constitute a quorum. Shares represented by valid proxies (in the case of stockholders) or valid CDI voting instruction forms (in the case of CDI holders) will be treated as present at the Annual Meeting for purposes of determining a quorum, without regard to whether the proxy is noted as casting a vote or abstaining. Shares represented by broker non-votes will be treated as present for purposes of determining a quorum. Shares voted by a broker on any issue other than a procedural motion will be considered present for all quorum purposes, even if the sharessuch Shares are not voted on every matter.

Votes Required

        As more fully described in this Proxy Statement:

•

Each nominee for director must receive a majority of the votes cast on his or her nomination to be elected;



•

Approval of a non-binding, advisory resolution approving the compensation of ourthe individuals listed in the Summary Compensation Table on page 69 of this Proxy Statement, or the Named Executive Officers, as described in this Proxy Statement requires the affirmative vote of a majority of the votes cast on the proposal; and



•

Approval of the proposal to ratify the selection of the Company's independent registered public accounting firm requires the affirmative vote of a majority of the votes cast on the proposal.

Abstentions and Broker Non-Votes

        A "broker non-vote" occurs on an itema proposal when a broker identified as the record holder of sharesShares is not permitted by the rules of the New York Stock Exchange, or the NYSE, to vote on that itemproposal without instruction from the beneficial owner of the sharesShares and no instruction has been received with respect to that item.proposal. Under the NYSE rules, brokers may vote on routine matters even without instructions from the street name holder. The election of directors and the advisory vote on executive compensation are not routine matters for purposes of broker voting. If you do not instruct your broker how to vote with respect to these items,proposals, your broker may not vote with respect to these proposals and your sharesShares will be counted as "broker non-votes." The ratification of the selection of our independent registered public accounting firm for the fiscal year ending December 31, 20162018 is a routine

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matter; therefore, there will be no broker non-votes in connection with that matter. CDN is not permitted to cast votes on any proposal unless specifically directed by the applicable CDI holder.

        A properly completed proxy and CDI voting instruction form, if received in time for voting and not revoked, will be voted at the Annual Meeting in accordance with the instructions contained therein, and, unlesstherein. Unless otherwise directed, the sharesShares represented by the proxy card will be voted:

•

"For" the election of the Board's nominees for director listed in this Proxy Statement;



•

"For" the approval of a non-binding, advisory resolution approving the compensation of our Named Executive Officers as described in this Proxy Statement; and



•

"For" the ratification of the selection by the Audit Committee of Deloitte & Touche LLP as the Company'sour independent registered public accounting firm for the year ending December 31, 2016.2018.

        Abstentions and broker non-votes will not be counted as votes cast and, therefore, will not affect the proposals that are being submitted to the Company's stockholders at the Annual Meeting.

        Although the advisory vote on the proposed resolution to approve the compensation of the Company'sour Named Executive Officers is non-binding, the Compensation Committee of the Board will consider the outcome of thesuch vote when making future compensation decisions for the Company's Named Executive Officers.our named executive officers.

Attendance at the Annual Meeting

        Attendance at the Annual Meeting or any adjournment or postponement thereof will be limited to stockholders and CDI holders of record of the Company as of the close of business5:00 p.m. U.S. Eastern Time on the Record Date (7:00 a.m. Australian Eastern Standard Time on April 18, 2018) and guests of the Company. If you are a stockholder or CDI holder of record of the Company as of the close of business5:00 p.m. U.S. Eastern Time on the Record Date (7:00 a.m. Australian Eastern Standard Time on April 18, 2018), your name will be verified against the list of stockholders or CDI holders, as applicable, of record prior to your admittance to the Annual Meeting or any adjournment or postponement thereof. Please be prepared to present photo identification for admission. If you hold your sharesShares in street name, you will need to provide proof of beneficial ownership, such as a brokerage account statement, a copy of a voting instruction form

provided by your custodian with respect to the Annual Meeting or other similar evidence of ownership, as well as photo identification, in order to be admitted to the Annual Meeting. Please note that if you hold your sharesShares in street name and intend to vote in person at the Annual Meeting, you must also provide a "legal proxy" obtained from your custodian. Each CDI holder may attend the Annual Meeting but cannot vote in person at the Annual Meeting unless such CDI holder is appointed as a proxy by CDN.

Revocability of Proxies

        Any stockholder giving a proxy in the manner set forth in the Notice of Internet Availability has the power to revoke such proxy at any time before it is exercised. If you are a registered holder of Common Stock,Shares, you may revoke a previously submitted proxy by voting over the internet or by telephone at a later time in the manner provided on the Website. Any such notice or vote must be received by 11:59 p.m. U.S. Eastern Daylight Time on June 16, 2016.13, 2018. You may also revoke your proxy by attending the Annual Meeting and voting in person.

        If you are a CDI holder and you direct CDN to vote by completing the CDI voting instruction form, you may revoke those directions online at www.linkmarketservices.com.au or by delivering to Link Market Services Limited, Locked Bag A14, Sydney South, New South Wales, Australia 1235, no later than 1:59 p.m. Australian Eastern Standard Time on June 11, 2018 (which is 11:59 p.m. U.S. Eastern Time on June 10, 2018).

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Please note, however, that only your last-datedlast dated proxy or CDI voting instruction will count,be counted, and any proxy or CDI voting instruction may be revoked at any time prior to its exercise at the Annual Meeting, as described in this Proxy Statement.

        If your sharesShares are held in the name of a brokerage firm, bank, nominee or other institution, and you have instructed your brokerage firm, bank, nominee or other institution to vote your shares,Shares, you must follow the instructions received from your brokerage firm, bank, nominee or other institution to change your voting instruction. Please contact your custodian for detailed instructions on how to revoke your voting instruction and the applicable deadlines.

Information Regarding the Company

        Our principal executive offices are located at One Federal Street, Boston, Massachusetts 02110.

        The Company's website address, www.ironmountain.com, is included several times in this Proxy Statement as a textual reference only, and the information in the Company's website is not incorporated by reference into this Proxy Statement.

Notice Regarding the Availability of Proxy Materials

        In accordance with rules and regulations of the Securities and Exchange Commission, or the SEC, instead of mailing a printed copy of our proxy materials to each stockholder of record, the Company may furnish proxy materials via the internet. Accordingly, all of the Company's stockholders, other than CDI holders, will receive a Notice of Internet Availability, which will be mailed on or about April 26, 2016.30, 2018.

        On the date of mailing the Notice of Internet Availability, stockholders will be able to access all of the proxy materials at www.materials.proxyvote.com/https://materials.proxyvote.com/46284v. The proxy materials will be available free of charge, and the Notice of Internet Availability will provide instructions as to how youstockholders may access and review all of the important information contained in the proxy materials (including the Company's Annual Report to stockholders)Stockholders) over the internet or through other methods specified on the Website. The Website contains instructions as to how tostockholders may vote by internet or over the telephone. The Notice of Internet Availability also instructs youstockholders as to how youthey may request a paper or email copy of the proxy card. If you receive a Notice of Internet Availability and would like to receive printed copies of the proxy materials, you should follow the instructions for requesting such materials included in the Notice of Internet Availability.

        All CDI holders will receive a printed copy of our proxy materials along with the CDI voting instruction form. If you are a CDI holder, you may also view and print these materials online at www.linkmarketservices.com.au. The CDI voting instruction form will provide instructions as to how CDI holders may access and review all of the important information contained in the proxy materials (including the Company's Annual Report to Stockholders) over the internet. The CDI voting instruction form contains instructions as to how CDI holders may direct CDN to vote on their behalf.

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ITEMPROPOSAL 1

ELECTION OF DIRECTORS

        The Board currently consists of ten (10)eleven (11) directors. Each current director serves foris currently serving a one-year term, and the term of each director will expire at the Annual Meeting.

        In September 2015, in connection with the Company's agreement, or the Recall Agreement, to acquire Recall Holdings Limited, or Recall, and conditioned on the consummation of the Company's acquisition of Recall, the Board increased the number of directors to twelve (12) and appointed Mr. Neil Chatfield and Ms. Wendy J. Murdock, each of whom currently serves as a non-executive director of Recall, to the Board. In accordance with the terms of the Recall Agreement, the Board also agreed to name Mr. Chatfield and Ms. Murdock as nominees to the Board to be voted on by the Company's stockholders at the first annual meeting of stockholders following the consummation of the Company's acquisition of Recall. The Company expects to complete the acquisition of Recall on May 2, 2016, and, consequently, the appointment of Mr. Chatfield and Ms. Murdock to the Board is expected to become effective on May 2, 2016. The term of each of Mr. Chatfield and Ms. Murdock will expire at the Annual Meeting.

At the Annual Meeting, all nominees areeach nominee is to be elected for a one-year termsterm to serve until the Company's 20172019 Annual Meeting of Stockholders, or until their successors aresuch nominee's successor is elected and qualified.

        The Board has selected as nominees the following twelve (12)eleven (11) individuals, all of whom are current directors of the Company (except for Mr. Chatfield and Ms. Murdock, each of whom is expected to become a director of the Company on May 2, 2016):Company: Jennifer Allerton, Ted R. Antenucci, Pamela M. Arway, Clarke H. Bailey, Neil Chatfield, Kent P. Dauten, Paul F. Deninger, Per-Kristian Halvorsen, William L. Meaney, Wendy J. Murdock, Walter C. Rakowich and Alfred J. Verrecchia. Each nominee has agreed to serve if elected, and management has no reason to believe that any of the nominees will be unavailable to serve. For more detail on the process our Board follows when selecting nominees, please see page 19.

Required VoteDirector Nominee Skills and Experience

        Each nominee for director must receive a majority of the votes cast on his or her nomination to be elected. This means a nominee will be elected to the Board only if the votes cast "For" such nominee's election exceed the votes cast "Against" such nominee's election, with abstentions and broker non-votes not counting as votes "For" or "Against." Under the Company's Bylaws, if the number of votes cast "For" a director nominee does not exceed the number of votes "Against" the director nominee, and if the nominee is an incumbent director, then he or she must promptly tender his or her resignation from the Board. Each incumbent director, and each of Mr. Chatfield and Ms. Murdock, has already tendered an irrevocable resignation that will be effective upon (1) the failure to receive the required number of votes for re-election at the Annual Meeting or any meeting of stockholders at which he or she faces re-election and (2) the acceptance of such resignation by the Board. The Board will decide within 90 days of the certification of the stockholder vote, through a process managed byand the Nominating and Governance Committee select director nominees on the basis of their integrity, experience, achievements, judgment, intelligence, personal character, ability to make independent analytical inquiries, willingness to devote adequate time to Board duties and likelihood that they will be able to serve on the Board for a sustained period. The Board and the Nominating and Governance Committee believe each director nominee should be well-versed in strategic oversight, corporate governance, stockholder advocacy, and leadership in order to be an effective member of the Board and excluding the nominee in question, whether to accept the resignation. The Board's explanation of its decision will be promptly disclosed in a filing with the SEC.Board.

        Brokers are not permitted to vote your shares for the election of directors absent instruction from you. Therefore, we urge you to give voting instructions to your broker on the proxy so that your votes may be counted on this important matter.

The Board recommends that you vote FOR the election of each of the Board's twelve (12) nominees to serve as directors of Iron Mountain until the 2017 Annual Meeting of Stockholders, or until their successors are elected and qualified.

Information Concerning the Directors and Director Nominees

        Set forth below is the name and age of each of our director nominees and his or her principal occupation as of April 15, 2016, as well as his or her business experience during the past five years and the names of certain other companies of which he or she currently serves as a director or has served as a director during the past five years. In addition to the information presented below regarding each nominee's specific experience, qualifications, attributes and skills that led our Board to the conclusion that he or she should serve as a director, we alsoWe believe that all of our director nominees havemeet these criteria. They bring a reputation for integrityfull array of business and sound judgmentleadership skills to their oversight responsibilities and excellent analytical skills. Each of our director nominees has demonstrated business acumenrepresent diverse skills and complementsexperiences, which the attributes and skillsBoard believes will contribute to the effective oversight of the other director nominees.Company.

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        More details about their background and experience can be found below. Each of the nominees has consented to be named in this Proxy Statement and to serve on the Board, if elected.

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Required Vote

        Each director nominee must receive a majority of the votes cast on his or her nomination to be elected. This means a director nominee will be elected to the Board only if the votes cast "For" such nominee's election exceed the votes cast "Against" such nominee's election, with abstentions and broker non-votes not counting as votes "For" or "Against." Under the Company's Bylaws, if the number of votes cast "For" a director nominee does not exceed the number of votes "Against" the nominee, and if the nominee is an incumbent director, then he or she must promptly tender his or her resignation from the Board. Each incumbent director has already tendered an irrevocable resignation that will be effective upon (1) the failure to receive the required number of votes for re-election at the Annual Meeting or any meeting of stockholders at which he or she faces re-election and (2) the acceptance of such resignation by the Board. The Board annually elects the officerswill decide within 90 days of the Company. Each officer holds office atcertification of the discretionstockholder vote, through a process managed by the Nominating and Governance Committee of the Board, or the Nominating and Governance Committee, and excluding the director nominee in question, whether to accept the resignation. The Board's explanation of its decision will be promptly disclosed in a filing with the SEC.

        Brokers and CDN are not permitted to vote your Shares for the election of directors absent instruction from you. Therefore, we urge you to give voting instructions to your broker on the proxy, or, in the case of CDI holders, give voting instructions to CDN, so that your votes may be counted on this important matter.

The Board recommends that you vote FOR the election of each of the Board's eleven (11) nominees to serve as directors of Iron Mountain until the first meeting2019 Annual Meeting of the Board following the next annual meeting of stockholdersStockholders, or until such officer sooner dies, resigns or is removed. Theretheir successors are no family relationships between or among any of the Company's officers or directors.elected and qualified.

        Set forth below is the name and ageTable of each of our executive officers who is not nominated to be a director of the Company, his or her principal occupation and business experience during the past five years and the names of certain other companies of which he or she served as a director, as of April 15, 2016.

        Our Board is composed of a majority of directors who qualify as independent directors pursuant to the corporate governance standards for companies listed on the NYSE. The Board evaluates independence pursuant to NYSE standards each year by affirmatively determining whether each director has a direct or indirect material relationship with the Company (including its subsidiaries) and members of the Company's management that may interfere with such director's ability to exercise his or her independence from the Company. When assessing the materiality of a director's relationship with the Company, the Board considers all relevant facts and circumstances, not merely from the director's standpoint but from that of the persons or organizations with which the director has an affiliation. Material relationships can include commercial, industrial, banking, consulting, legal, accounting, charitable and familial relationships. None of our independent directors (other than Mr. Deninger) has any relationship with the Company or its management other than his or her service as a director and on committees of the Board, and the Board has concluded that none of the Company's directors possess the objective relationships set forth in the NYSE listing standards that prevent independence.

        In assessingWhen evaluating the independence of Mr. Deninger,director nominees, the Board considered Mr. Deninger's position as a senior managingweighs numerous factors, including the effect of multiple years of service on the ability of our director at Evercore Partners Inc., or Evercore.nominees to maintain independence. In 2013particular, the Company entered into an agreementBoard weighed the potential impact of tenure on the independence of our two longest serving directors, Messrs. Bailey and Dauten. Messrs. Bailey and Dauten have significant experience serving on the Board under different operating environments and with Evercore pursuantdifferent management teams, including under two prior chief executive officers. The Board concluded that Messrs. Bailey and Dauten continue to which Evercore agreed to provide financial advisory services tobe effective directors who fulfill their responsibilities with integrity and independence of thought. Therefore, the Company, as further described under the "Certain Relationships and Related Transactions" section of this Proxy Statement. In 2015 the Company paid the final $250,000 of fees associated with the agreement with Evercore. The agreement with Evercore has terminated in accordance with its terms. The Board determined that because Mr. Deninger agreed to waive any direct fees he may receive in connection with the Evercore engagement and did not work on the engagement on behalf of Evercore, this relationship would not interfere with Mr. Deninger's ability to exercisetheir independence from the Company.management has not been diminished by their years of service.

        The Board has determined that all of our non-management directors who served in 2017 qualify as independent under NYSE rules.rules, including Mr. Chatfield who resigned effective September 8, 2017. One of our directors, Mr. Meaney, is a management employee involved in our day-to-day activities and is not considered to be an independent director.

        Attendance.    During the fiscal year ended December 31, 2015, the Board held 13 meetings. Each incumbent director attended at least 75% of the aggregate number of meetings of the Board and all committees thereof on which such director served that were held during the period for which such director served. Mr. Chatfield and Ms. Murdock are expected to join the Board on May 2, 2016 and did not attend any Board and committee meetings during the fiscal year ended December 31, 2015. All of our directors standing for re-election at the time attended our 2015 Annual Meeting of Stockholders. All directors standing for re-election are expected to attend the Annual Meeting, either in person or by teleconference. Our policy with respect to directors' attendance at our annual meetings of stockholders can be found in our Corporate Governance Guidelines, the full text of which appears under the heading "Company/Investors/Corporate Governance" on our website at www.ironmountain.com.

Board Leadership Structure

        The Board does not have a formal policy as toon whether the roles of Chairman and CEO should be combined or separated. The Board believes that Iron Mountain stockholders are best served by the Board having flexibility to consider the relevant facts and circumstances and determine, at the time of the Chairman's election, the best leadership structure for the Company rather than by adhering to a formal standing policy on the subject.

        As a result of the Board's ongoing review of its leadership structure, theThe Board has determined that the position of Chairman should be held by a non-employee of the Company. The Board believes that the current leadership structure, which separates the roles of CEO and Independent Chairman, fosters effective governance and oversight of the Company. The Independent Chairman controls the Board meeting agendas, which ensures that topics deemed important by the independent directors are included in Board discussions and best enables the Board to express its views on our management, strategy and execution. The Independent Chairman is responsible for advising the CEO and presiding over meetings of the Board, presiding over all executive sessions of non-management directors, consulting with the CEO on Board meeting agendas and acting as a liaison between management and non-management directors. The CEO is responsible for setting the Company's strategy and leading the organization's day-to-day performance. We believe this governance structure promotes balance between the authority of those who oversee our business and those who manage it on a day-to-day basis.

defined by the rules of the SEC and is financially literate as defined by the NYSE listing standards. The Audit Committee: (1) assists the Board in oversight of the integrity of the Company's financial statements; (2) assists the Board in oversight of the Company's compliance with legal and regulatory requirements; (3) assists the Board in the oversight of the Company's compliance with requirements with respect to maintaining the Company's qualification for taxation as a REIT; (4) assists the Board in oversight of the independent registered public accounting firm's retention, qualifications and independence; (4)(5) assists the Board in oversight of the performance of the Company's internal audit function and independent auditors; (5)(6) prepares an Audit Committee report as required by the SEC to be included in the annual Proxy Statement; (6)(7) reviews and evaluates the lead audit partner of the independent registered accounting firm; (8) performs such other duties as the Board may assign to the Audit Committee from time to time, such as approving transactions subject to our Related Person Transaction Policies and Procedures described on page 7318 of this Proxy Statement; and (7)(9) takes other actions to meet its responsibilities as set forth in its written charter. The Audit Committee is also responsible for establishing procedures for the receipt, retention and treatment of complaints regarding accounting, internal accounting controls and auditing matters, including procedures for the confidential and anonymous submission by employees of the Company of any concerns regarding accounting or auditing matters they think may be questionable. Information about these procedures can be found on our website, www.ironmountain.com, under the heading "Company/Investors/Corporate Governance."

        Compensation Committee.    Each member of the Compensation Committee qualifies as independent under the NYSE listing standards. The Compensation Committee: (1) reviews, approves and recommends to the independent members of the Board the annual compensation, including base salary, equity-based incentives and the payment of short-term incentive compensation, for the CEO; (2) approves all long-term equity incentives to our employees, including Messrs. Day, Duale, Meaney and Keddy and Ms. Evens, or, collectively, the Named Executive Officers, under the 2014 Stock and Cash Incentive Plan, as amended, or the 2014 Plan; (3) reviews and approves the annual cashcompensation, including base salary, equity-based incentives and the payment of short-term incentive compensation, for Named Executive Officers (other

than the CEO) based on recommendations from the CEO and reports to the Board on such decisions; (4) reviews the Company's cash and stock-based incentive compensation plans to assess their effectiveness in meeting the Company's goals and objectives and exercises all of the authority of the Board with respect to the administration of such plans; (5) annually reviews and discusses with management a draft of the Company's Compensation Discussion and Analysis to be included in the Company's Annual Report on Form 10-K and annual proxy statement; (6) annually prepares and publishes an annual report of the Compensation Committee for inclusion in the Company's Annual Report on Form 10-K and annual proxy statement; (7) reviews and discusses at least on an annual basis the risks arising from the Company's compensation policies for its employees; (8) reviews and (8)discusses "pay ratio" disclosure for inclusion in the Company's Annual Report on Form 10-K and annual proxy statement; and (9) takes other actions to meet its responsibilities as set forth in its written charter.

        The Board has delegated final authority for compensation decisions for the Named Executive Officers, other than our CEO, to the Compensation Committee. The Compensation Committee has the authority to delegate any of its responsibilities to a sub-committee composed of members of the Compensation Committee, but it has not done so to date.

        For a discussion concerning the process and procedures for determining executive compensation and the role of executive officers and compensation consultants in determining or recommending the amount or form of compensation, see the "Compensation Discussion and Analysis" section in this Proxy Statement.

        Nominating and Governance Committee.    Each member of the Nominating and Governance Committee qualifies as independent under the NYSE listing standards. To ensure that the Nominating and Governance Committee has insight into the functioning of the standing committees, each committee chair is a member of the Nominating and Governance Committee. The Nominating and

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Governance Committee: (1) recommends the composition of the Board; (2) identifies and recommends candidates for nomination to the Board; (3) recommends to the Board structures and statements of the duties and responsibilities of each committee of the Board; (4) develops and recommends to the Board and implements corporate governance guidelines applicable to the Company; (5) assists the Board in annually reviewing management succession; (6) develops and monitors an annual process to assess the effectiveness of the Board and implements and oversees an annual review of the performance of the Board (including evaluations of individual Board members) and each of the Board's standing committees; (7)(6) develops and proposes, for approval by the Board, compensation policies for the Company's non-employee directors; (8)(7) annually reviews contributions to candidates made by the Iron Mountain Incorporated Political Action Committee, or IMPAC, and determines the composition of the IMPAC board; (8) annually reviews the Company's Political Contributions Policy and the Company's compliance with that policy; and (9) takes other actions to meet its responsibilities as set forth in its written charter.

        Finance Committee.    Although the NYSE listing standards do not require members of the Finance Committee to be independent, all members of the Finance Committee qualify as independent under the NYSE listing standards and the Board's assessment of any material relationships with the Company. The Finance Committee: (1) reviews and provides recommendations with respect to the Company's capital structure, leverage and financial strategies; (2) reviews the Company's material capital allocation decisions, strategic investments and dispositions and other opportunities for maximizing stockholder value;value and periodically reviews and evaluates the performance of and returns on investments and dispositions approved by the Board; (3) considers, reviews and reviewsprovides recommendations to the Board with respect to the Company's dividend and share repurchase policies and programs and other strategies to return capital to stockholders; (4) reviews and approves the Company's derivatives and hedging policies and strategies; (5) reviews the Company's investment policies and practices; (6) reviews the Company's credit ratings and strategy,strategy; (7) periodically reviews the Company's investor relations strategy,strategy; (8) furnishes periodic reports to the Board concerning the Finance Committee's work; and (9) performs such other duties as the Board may assign to the committee from time to time.

        Risk and Safety Committee.    Although the NYSE listing standards do not require the members of the Risk and Safety Committee to be independent, all members of the Risk and Safety Committee qualify as independent under the NYSE listing standards. The Risk and Safety Committee (1) reviews andbased on reports provided by the Company's management, monitors (A) the adequacy of material fire, health, safety, security, business continuity, cyber security, chain of custody and information security and risk management strategies and systems;systems for the reporting of accidents, incidents and risks, and (B) material investigations and remedial actions, as appropriate; (2) reviews the Company's establishment and monitors material safety, security, business continuity, information security andoperation of its enterprise-wide risk management, policiesor ERM, program which is designed to identify, assess, monitor and processes implemented, establishedmanage risk throughout the Company, and reported on byincludes an annual management ERM report to the Company's

management;Board; (3) monitors the Company's insurance programs;program; and (4) takesexamines any other actionsmatters referred to meet its responsibilities as set forth in its written charter.it by the Board.

Board and Committee Evaluations

        The Nominating and Governance Committee oversees the Board and committee evaluation process. Generally, including in 2015, the Board and each committee conduct self-evaluations by means of written questionnaires completed by each director and committee member. The anonymous responses are summarized and provided to the Board and each committee at their subsequent meetings in order to facilitate an examination and discussion by the Board and each committee of the effectiveness of the Board, committees, individual directors, Board and committee structure and dynamics, and areas for possible improvement. The Nominating and Governance Committee establishes the boardBoard and committee evaluation process each year and may determine to use an independent third party evaluation process from time to time in the future.

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The Board's Role in Risk Oversight

        The Board is responsible for oversight of the Company's management of enterprise risks. Iron Mountain senior management is responsible for the Company's risk management process and the day-to-day supervision and mitigation of enterprise risks. TheWe have a comprehensive risk management program, where our senior executive team is provided regular reports by our operational teams and standing committees on enterprise risk, emerging trends and issues. Our senior executive team reviews and prioritizes significant risks, allocates resources for mitigation and provides the Board receiveswith regular reports on areas of materialpotential Company risk, including strategic, operational, information security, human resources, financial, legal, compliance, REIT and regulatory risks. The Board, or the committee of the Board assigned responsibility for a specific area of risk, receives reportsupdates from the Company executive accountable for understanding and mitigating the identified risk. When a committeeThe chair of the Board receives a risk report, the chairman of sucheach committee provides a summary of the discussion to the Board of such committee's risk discussions during the next regularly scheduled Board meeting. The Board also formally reviews the Company's overall risk position and risk management processes at least annually. This practice allows the Board and each of its committees to remain coordinated in their oversight of enterprise risk. The Risk and Safety Committee provides additional support to the Board in ensuringto ensure that the Company's enterprise risk management program is established appropriatelyincludes the enterprise risk management framework, that the Company's governance structures are appropriate and operating effectively.effectively and to ensure sufficient expertise and continuity between the Board's annual reviews. The key responsibilities of the Risk and Safety Committee and the risk oversight of other committees are further detailed on page 16.

The Board's Role in Management Succession

        The Board oversees the recruitment, development, and retention of executive talent. Management succession is generally discussed at Board meetings throughout the year with the CEO, as well as in executive sessions. Management succession discussions generally focus on the CEO and other senior executive roles and also include broader discussions on the Company's workforce. The Board also has regular and direct exposure to senior leadership and high-potential employees through meetings held throughout the year.

The Board's Role in Setting Compensation and Assessing Compensation Risk

        The Compensation Committee reviews the executive compensation program throughout the year with the assistance of an independent compensation consultant. For a more detailed discussion on this topic, please see the "Compensation Discussion and Analysis" section of this Proxy Statement.

Code of Ethics

        Our Code of Ethics and Business Conduct applies to each of the Company's employees, including officers, and directors. Our Code of Ethics and Business Conduct is posted on our website, www.ironmountain.com, under the heading "Investors/Corporate Governance." A printed copy of our Code of Ethics and Business Conduct is also available free of charge to any stockholder who requests a copy. We intend to disclose any amendment to, or waiver from, a provision of our Code of Ethics and Business Conduct applicable to our CEO, chief financial officer or principal accounting officer or controller by posting such information on our website. Any waivers applicable to any other executive officers will also be promptly disclosed to stockholders on our website.

Political Expenditures

        Our Global Political Contribution Policy, together with our Code of Ethics and Business Conduct, guide our approach to ethical business behavior and corporate political contributions. Our Global Political Contribution Policy provides that Iron Mountain does not make political contributions in any

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form or amount from corporate funds or resources, even when permitted by applicable law. This means corporate funds are not used in support of or opposition to political candidates, political parties, political committees and other political entities organized and operating for political candidates. In addition, corporate funds are not used for "electioneering" communications.

        The Company administers IMPAC, which is a non-partisan political action committee supporting congressional candidates at the federal level only. IMPAC allows eligible employees to pool their resources to support candidates who understand the issues important to the Company's business and its employees. Participation in IMPAC is strictly voluntary. Except for administrative expenses, IMPAC is funded solely by the Company's employees and directors and is not supported by funds from the Company. IMPAC complies with federal election laws and all other applicable laws and reports regularly to the Federal ElectionsElection Commission. In addition, IMPAC is governed by a set of bylaws and supervised by a board of directors composed of senior managers from different areas of the Company.

        The Company is a member of a number of trade associations that participate in public relations activities such as education and conferences, but not for the purpose of making political contributions. Our Code of Ethics and Business Conduct and our Global Political Contribution Policy are available on our website under the heading "Company/Investors/"Investors/Corporate Governance."

Certain Relationships and Related Transactions

        The Board has adopted a written Related Person Transaction Policies and Procedures, or the Related Persons Policy, which provides that all transactions with related persons are subject to approval or ratification by our Audit Committee. With certain exceptions, the Related Persons Policy provides that the Audit Committee shall review the material facts of all transactions with related persons and either approve or disapprove of the transaction. Under the Related Persons Policy, transactions covered include all transactions involving the Company, amounts in excess of $120,000 and a Related Person (a term that includes executive officers, directors, nominees for election as directors, beneficial owners of 5% or more of the Company's outstanding Common Stock and immediate family members of the foregoing). The Audit Committee will determine whether the terms of a covered transaction are fair to the Company and no less favorable to the Company than would be generally available absent the relationship with the counterparty, whether there are business reasons for the transaction, whether the transaction impairs the independence of an outside director, whether the transaction would represent an improper conflict of interest and whether the transaction is material, among other considerations. In the event that prior approval of a covered transaction is not feasible, the Related Persons Policy provides that a transaction may be approved by the chair of the Audit Committee in accordance with such policy. The chair shall report any such approvals at the next Audit Committee meeting. If the Company becomes aware of a transaction with a Related Person that has not been approved by the Audit Committee prior to its consummation, the Audit Committee shall review such transaction and evaluate all possible options, including ratification, revision or termination of such transaction and shall take such action as it deems appropriate under the circumstances. The Related Persons Policy is intended to supplement, and not supersede, our other policies and procedures with respect to transactions with Related Persons. There were no new transactions with related persons that required the review of our Audit Committee in 2017.

Corporate Responsibility

        We are committed to transparent reporting on sustainability and corporate responsibility efforts in accordance with the guidelines of the Global Reporting Initiative. Our corporate responsibility report highlights our progress against key measures of success for our efforts in the community, our environment, and for our people. We are a trusted partner to approximately 95% of the Fortune 1000. Iron Mountain is a member of the FTSE4 Good Index, Dow Jones Sustainability Index, MSCI World ESG Index, MSCI ACWI ESG Index and MSCI USA IMI ESG Index, each of which include

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companies that meet globally recognized corporate responsibility standards. A copy of our corporate responsibility report is available on the "About Us" section of our website, www.ironmountain.com, under the heading "Corporate Social Responsibility."

Stockholder Communications towith the Board of Directors

        The Board believes it is important to engage effectively with stockholders. To facilitate this engagement, in February 2016, the Board adopted a written Shareholder Engagement and Communication Policy, or the Shareholder Engagement Policy, which outlines the procedures for the Board's engagement and communication with the Company's stockholders. The Shareholder Engagement Policy is overseen by the Nominating and Governance Committee. Under the Shareholder Engagement Policy, any stockholder, CDI holder, security holder or other interested party who desires to communicate with the Board, any individual director, including the Independent Chairman, or the independent or non-management directors as a group, may do so by regular mail or email directed to the Secretary of the Company. Communications to the Board should be mailed to Corporate Secretary, Iron Mountain Incorporated, One Federal Street, Boston, Massachusetts 02110; the Secretary's email address is corporatesecretary@ironmountain.com. Upon receiving such mail or email, the Secretary will assess the appropriate director or directors to receive the message and will forward the mail or email to such director or directors without editing or altering it.

Selection of Board of Directors Nominees

        The Board is responsible for developing and approving criteria, in addition to those set forth in our Corporate Governance Guidelines, for candidates for Board membership. The Nominating and Governance Committee is responsible for seeking candidates to become Board members, consistent with the criteria set forth in the Corporate Governance Guidelines and approved by the Board, and for recommending candidates to the entire Board for selection by the Board for nomination to fill vacancies on the Board or expiring terms of directors at each annual meeting of stockholders. The Board as a whole is responsible for nominating individuals for election to the Board by the stockholders and for filling vacancies on the Board that may occur between annual meetings of the stockholders.

        Nominees for director will be selected on the basis of their integrity, experience, achievements, judgment, intelligence, personal character, ability to make independent analytical inquiries, willingness to devote adequate time to Board duties and likelihood that they will be able to serve on the Board for a sustained period. In connection with the selection of nominees for director, the Board's policy is to give due consideration to the Board's overall balance of diversity of perspectives, backgrounds and experiences. To implement and review the effectiveness of our diversity policy, the Nominating and Governance Committee reviews the appropriate skills and characteristics of members of the Board in the context of the then current composition of the Board. It is the practice of the Nominating and Governance Committee to then consider these factors when screening and evaluating candidates for nomination or re-election to the Board. The Board will not nominate for election as director any candidate who has not agreed to tender, promptly following the annual meeting at which he or she is elected as director, an irrevocable resignation that will be effective upon (1) the failure to receive the required number of votes for re-election at the next annual meeting of stockholders at which he or she faces re-election, and (2) acceptance of such resignation by the Board.

        The Nominating and Governance Committee will consider, as part of the process for identifying individuals who might be candidates, individuals who are properly recommended by stockholders for nomination by the Board at a meeting of stockholders at which directors are to be elected. To be proper, a recommendation for a nominee for director with respect to a meeting of stockholders must comply with applicable law, the Company's Bylaws and the Company's Corporate Governance Guidelines. The Nominating and Governance Committee will consider any suggestions offered by other

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directors or stockholders with respect to potential directors, and there will be no difference in the manner in which potential nominees are evaluated. However, the Nominating and Governance Committee and the Board are not required to enlarge the size of the Board in order to nominate an otherwise fully qualified candidate proposed by a stockholder. A stockholder wishing to nominate a

director directly must comply with the procedures described in the Company's Bylaws and this Proxy Statement.

        In 2015 the Nominating and Governance Committee did not retain the services of, and did not pay a fee to, any third party to identify or assist in identifying or evaluating potential nominees to our Board.

Nominations and Proposals of Stockholders

        A stockholder who, in accordance with Rule 14a-8, or Rule 14a-8, under the Securities Exchange Act of 1934, as amended, or the Exchange Act, wants to present a proposal for inclusion in the Company's 20172019 Proxy Statement and proxy card relating to the 20172019 Annual Meeting of Stockholders must submit the proposal by December 28, 2016.29, 2018. In order for the proposal to be included in the Proxy Statement, the stockholder submitting the proposal must meet certain eligibility standards and comply with certain regulations established by the SEC.

        Stockholders who wish to present a business proposal or nominate persons for election as directors at the Company's 20172019 Annual Meeting of Stockholders must provide a notice of the business proposal or nomination in accordance with Section 2.4 of our Bylaws, in the case of business proposals, or Section 3.2 of our Bylaws, in the case of director nominations. In order to be properly brought before the 20172019 Annual Meeting of Stockholders, Sections 2.4 and 3.2 of our Bylaws require that a notice of the business proposal the stockholder wishes to present (other than a matter brought pursuant to Rule 14a-8), or the person or persons the stockholder wishes to nominate as a director, must be received at our principal executive office not less than 90 days, and not more than 120 days, prior to the first anniversary of the Company's prior year's annual meeting. Therefore, any notice intended to be given by a stockholder with respect to the Company's 20172019 Annual Meeting of Stockholders pursuant to our Bylaws must be received at our principal executive office no earlier than February 17, 201715, 2019 and no later than March 19, 2017.17, 2019. However, if the date of our 20172019 Annual Meeting of Stockholders occurs more than 30 days before or 30 days after June 17, 2017,14, 2019, the anniversary of the 20162018 Annual Meeting of Stockholders, a stockholder notice will be timely if it is received at our principal executive office by the later of (1) the 120^th120th day prior to such annual meeting or (2) the close of business on the tenth day following the day on which public disclosure of the date of the meeting was made. To be in proper form, a stockholder's notice must include the specified information concerning the stockholder and the business proposal or nominee, as described in Sections 2.4, 3.2 and 3.3 of our Bylaws.

        All proposals must be mailed to the Company's principal executive office, at the address stated herein, and should be directed to the attention of the Secretary of the Company.

Code of EthicsExecutive Officers

        Our CodeThe Board annually elects the officers of Ethics and Business Conduct applies to eachthe Company. Each officer holds office at the discretion of the Board until the first meeting of the Board following the next annual meeting of stockholders or until such officer sooner dies, resigns or is removed. There are no family relationships between or among any of the Company's employees, including officers or directors.

        Set forth below is the name and directors. Our Codeage of Ethics and Business Conduct is posted on our website, www.ironmountain.com, under the heading "Company/Investors/Corporate Governance." A printed copyeach of our Codeexecutive officers who is not nominated to be a director of Ethics and Business Conduct is also available free of charge to any stockholder who requests a copy. We intend to disclose any amendment to,the Company, or, waiver from, a provision of our Code of Ethics and Business Conduct applicable totogether with our CEO, chief financial officerour Executive Officers, his or her principal accounting officeroccupation and business experience during the past five years and the names of certain other companies of which he or controller by posting such information on our website. Any waivers applicable to any other executive officers will also be promptly disclosed to stockholders on our website.she served as a director, as of April 20, 2018.

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ITEMPROPOSAL 2

ADVISORY VOTE ON THE COMPENSATION OF OUR NAMED EXECUTIVE OFFICERS

        In accordance with the requirements of Section 14A of the Exchange Act and related rules of the SEC, we are including this separate proposal subject to stockholder votefor stockholders to approve, on a non-binding, advisory basis, the compensation of our Named Executive Officers listed in the "SummarySummary Compensation Table"Table appearing inon page 69 of this Proxy Statement, as disclosed in this Proxy Statement pursuant to Item 402 of Regulation S-K.Statement.

        Our executive compensation is designed to reward executive performance that contributes to our success while encouraging behavior that is in our and our stockholders' long-term best interests. We also seek to attract, motivate, reward and retain the senior management talent required to achieve our corporate objectives and increase stockholder value. At the core of our executive compensation programs is our "pay for performance" philosophy that links competitive levels of compensation to achievements of our overall strategy and business goals, as well as predetermined objectives. We believe our compensation program is strongly aligned with the interests of our stockholders and sound corporate governance principles. We urge you to read the "Compensation Discussion and Analysis" section of this Proxy Statement and compensation tables and narrative discussion in this Proxy Statement for additional details on our executive compensation, including our compensation philosophy and objectives and the compensation of our Named Executive Officers.

        The vote on this proposal is not intended to address any specific element of compensation; rather, the vote relates to the compensation of our Named Executive Officers, as described in this Proxy Statement in accordance with the compensation disclosure rules of the SEC. To the extent there is any significant vote against the compensation paid to the Named Executive Officers as disclosed in this Proxy Statement, the Compensation Committee will evaluate whether any actions are necessary to address the concerns of stockholders.

        Based on the above, we request that you indicate your support for our executive compensation philosophy and practices by voting to approve, on a non-binding, advisory basis, the following resolution:

        "RESOLVED, that the compensation paid to the Company's Named Executive Officers, as disclosed pursuant to Item 402 of Regulation S-K, including the Compensation Discussion and Analysis, compensation tables and narrative discussion in the Proxy Statement for the 20162018 Annual Meeting of Stockholders, is hereby APPROVED."

Required Vote

        The affirmative vote of a majority of the votes properly cast at the Annual Meeting is required to approve the advisory vote on the compensation of our Named Executive Officers, as described in the "Compensation Discussion and Analysis" section of this Proxy Statement, the compensation tables and the other narrative compensation disclosures contained in this Proxy Statement. For the purpose of determining whether a majority of the votes has been cast in favor of the approval of this resolution, only those cast "For" or "Against" are included, and any abstentions or broker non-votes will not count in making that determination. The opportunity to vote on this resolution is required pursuant to Section 14A of the Exchange Act. However, as an advisory vote, the vote on this resolution is not binding upon the Company and serves only as a recommendation to ourthe Board. Nonetheless, the Compensation Committee, which is responsible for designing and administering our executive compensation programs, and the Board value the opinions expressed by stockholders and will consider the outcome of the vote when making future compensation decisions for our Named Executive Officers.named executive officers.

        Our current policy is to provide stockholders with an opportunity to approve the compensation paid to our Named Executive Officers each year at our annual meeting of stockholders. We currently expect that the next such vote will occur at our 20172019 Annual Meeting of Stockholders.

        The Board recommends that you vote FOR the approval of the foregoing non-binding, advisory resolution approving the compensation of our Named Executive Officers.

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ITEMPROPOSAL 3

RATIFICATION OF THE SELECTION OF
INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

        Subject to ratification by the stockholders, the Audit Committee has selected the firm of Deloitte & Touche LLP as the Company's independent registered public accounting firm for 2018.

        The Audit Committee is directly responsible for the appointment, compensation, retention and oversight of the Company's independent auditors for the purpose of preparing or issuing audit reports or performing other audit reviews or test services. Our independent auditors report directly to the Audit Committee, and the Audit Committee has executive sessions with the independent auditors at each regularly scheduled Audit Committee meeting.

        The Audit Committee evaluates the performance of the Company's independent auditors each year and determines whether to reengage the current year.independent auditors or consider other audit firms. In doing so, the Audit Committee considers the quality and efficiency of the services provided by the auditors and the auditors' technical expertise and knowledge of the Company's operations and industry. In accordance with the Audit Committee charter, the Audit Committee also evaluates the independence of the independent auditors and discusses with the auditor its independence from the Company and its management. The Audit Committee also oversees compliance with the mandated five-year rotation of the independent auditors' lead engagement partner and reviews and evaluates the lead audit partner, and the chair of the Audit Committee is directly involved in the selection of any new lead engagement partner.

        Based on this evaluation, the Audit Committee has appointed Deloitte & Touche LLP to serve as independent auditors for the fiscal year ending December 31, 2018. Deloitte & Touche LLP has served as the Company's independent auditors since 2003 and is considered by management and the Audit Committee to be well qualified. Further, the Audit Committee and the Board believe that the continued retention of Deloitte & Touche LLP to serve as the independent registered public accounting firm is in the best interests of the Company and its stockholders.

        The Audit Committee has determined to submit its selection of the independent auditors to the Company's stockholders for ratification. This vote will ratify prior action by the Audit Committee and will not be binding upon the Audit Committee. However, the Audit Committee may reconsider its prior appointment of the independent auditors or consider the results of this vote when it determines to appoint the Company's independent auditors in the future.

        The Audit Committee oversees and is ultimately responsible for the outcome of audit fee negotiations associated with the Company's retention of its independent auditors. The fees we paid to Deloitte & Touche LLP in 2017 are shown in the table appearing on page 84 of this Proxy Statement.

        Representatives of Deloitte & Touche LLP are expected to be present at the Annual Meeting. They will have the opportunity to make a statement if they desire to do so and will be available to respond to appropriate questions from stockholders who are present at the Annual Meeting.

        The fees we paid to Deloitte & Touche LLP in 2015 are shown in the table appearing on page 75 of this Proxy Statement.

If the stockholders do not ratify the selection of Deloitte & Touche LLP as the Company's independent registered public accounting firm, the selection of accountants will be reconsidered by the Audit Committee.

Required Vote

        The affirmative vote of holders of a majority of the votes properly cast at the Annual Meeting is required to ratify the selection of Deloitte & Touche LLP to serve as the Company's independent registered public accounting firm for the current fiscal year. For purposes of determining the number of votes cast, only those cast "For" or "Against" are included, and any abstentions will not count in making that determination.

        The Board recommends that you vote FOR the ratification of the selection of Deloitte & Touche LLP.

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SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

        The following table sets forth certain information known to the Company with respect to beneficial ownership of Common Stock by: (1) each director and nominee for director; (2) the Named Executive Officers; (3) all directors and executive officersExecutive Officers of the Company as a group; and (4) each stockholder known by us to be the beneficial owner of more than 5% of the Common Stock. Such information is presented as of March 31, 2016,2018, except as otherwise noted.

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Equity Compensation Plan InformationEQUITY COMPENSATION PLAN INFORMATION

        The following provides certain equity compensation plan information with respect to all of our equity compensation plans in effect as of December 31, 2015:2017:

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EXECUTIVE COMPENSATION
COMPENSATION DISCUSSION AND ANALYSIS

Executive Summary

        The primary objectives of our compensation programs are to reward the achievement of both Company and individual goals and to align the interests of our executives with the creation of stockholder value. In keeping with these objectives, our compensation programs are designed to align with the objectives of our strategic plan developed by senior leadership, or the Strategic Plan, and reward teamwork and contribution to the successful achievement of our enterprise goals and financial objectives.

20152017 Developments

•

Reaffirmed ourWe continued to execute the Strategic Plan which is focused onto shift our revenue mix to faster growing businesses, making demonstrable gains in each of the three core pillars for growth—growth and value pillars: Developed Markets⁽¹⁾, Emerging Markets⁽²⁾, and Adjacent Businesses⁽³⁾; extended



•

In developed markets, our financial outlooksuccessful revenue management efforts drove strong internal storage revenue growth; we continue to 2020 atmaintain revenue growth from existing customers through revenue management programs and sales of services and focus on volume growth from further penetration of unvended customers such as those in the mid-market and U.S. federal government vertical market segments



•

We shifted our Investor Day in October 2015; and embarkedrevenue mix toward fast-growing businesses:



•

Emerging markets now represent more than 18% of total revenue, on a multi-year2014 constant currency basis, almost double the relative size from four years ago. Our progress was supported by strong internal growth and acquisitions;



•

We expanded our data center business through investments, acquisition and organic growth; in 2017, due to the growth of our data center business, we reclassified the business as a separate reportable operating segment; and



•

We continued to grow our other Adjacent Businesses, including entertainment and fine art storage and services



•

We achieved synergies from the Recall acquisition and the transformation program,initiative we began in 2015, or the Transformation Program, intendedInitiative, continuing to improve operational efficiencyproduce savings that allowed the Company to invest in data centers, Adjacent Businesses, innovation and provide additional investment fordividend growth



•

Entered into agreement to acquire Recall, which is expected to deliver meaningful synergies and earnings accretion once completed



•

AchievedWe achieved operational performance generally in line with expectations measured in constant currency; however,

⁽¹⁾

"Developed Markets" include United States, Canada, Western Europe, Australia, and New Zealand.

⁽²⁾

"Emerging Markets" include Central and Eastern Europe, Latin America, Africa, and Asia (excluding Australia and New Zealand).

⁽³⁾

"Adjacent Businesses" primarily include our entertainment, fine art and consumer storage and services businesses. For the strengtheningpurposes of our Strategic Plan and the U.S. dollar negatively impactedevaluation of performance under our reported resultscompensation programs, "Adjacent Businesses" include our data center business, which was part of our Adjacent Businesses reporting segment until the fourth quarter of 2017, at which time data centers became its own reporting segment.

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•

ContinuedWe continued to deliver rewards through our pay-for-performancepay for performance model that balances short-term operational performance and the creation of long-term stockholder value:



•

our executives were rewarded for 20152017 operational performance through our short-term incentive programprogram; and



•

the value of our executives' long-term incentives, the largest portion of their compensation, declined significantly due to the declinebenefited from an increase in our share price during 2017, partially offset by underperformance of our performance units, or PUs, due to the continued strength of the U.S. dollar since 2015 and total stockholder return performance over the impact of the strengthening U.S. dollar on the performance of certain of our Performance Units, or PUs, which are measured on a reported basis (i.e., including the impact of currency fluctuation)three-year period ending in 2017

Leadership Transition

President, International

        As previously disclosed in our Proxy Statement for our 2017 Annual Meeting of Stockholders, effective March 31, 2017, Mr. Marc A. Duale resigned from his role as the Company's President, International, and the Company entered into a separation agreement and a separate advisory agreement with Mr. Duale. The separation agreement provides substantially the same severance benefits as are contained in Mr. Duale's amended and restated employment agreement. Beginning May 1, 2017, in accordance with the terms of the advisory agreement, the Company retained Mr. Duale to provide advisory services to the Company for an initial period of up to 12 months. Mr. Duale continues to provide advisory services to the Company, and the Company extended the term of the advisory agreement through May 1, 2019.

        Further information regarding Mr. Duale's agreements can be found under the "Compensation Discussion and Analysis—Components of Compensation—Employment Agreements—Marc Duale" and "—Severance Policy—Separation and Advisory Agreements with Marc Duale" sections of this Proxy Statement.

        In connection with Mr. Duale's resignation, Mr. Ernest W. Cloutier assumed the role of Executive Vice President & GM, International. In connection with his new role, Mr. Cloutier began an expatriate assignment on August 1, 2017. Further information regarding Mr. Cloutier's expatriate agreement can be found under the "Compensation Discussion and Analysis—Components of Compensation—Employment Agreements—Ernest Cloutier" section of this Proxy Statement.

Chief Technology Officer

        Ms. Fidelma Russo joined the Company on March 13, 2017 and assumed the role of Executive Vice President, Chief Technology Officer of the Company. The Compensation Committee approved the following compensation arrangement for Ms. Russo:

•

annual base salary of $485,000;



•

target short-term performance-based incentive opportunity equal to 70% of annual base salary;



•

initial awards of restricted stock units, or RSUs, with an aggregate grant date value of approximately $1,100,000 (approximately $900,000 awarded in March 2017 and approximately $200,000 awarded in February 2018);



•

an annual long-term incentive award with an aggregate grant date value of approximately $700,000 (awarded in March 2017), as follows:



•

RSUs corresponding to $210,000 in economic value;



•

stock options corresponding to $140,000 in economic value; and

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•

PUs corresponding to $350,000 in economic value, 50% of which are correlated with total stockholder return performance over a three-year period ending December 2019 and 50% of which are correlated with the Company's performance measured against financial goals over the same three-year period; and



•

eligibility to participate in the Severance Program (as defined herein).

Strategic Plan

        During 2015, we continued to make progress executing onWe developed the Strategic Plan which includes (i)in 2013 to focus our business strategy and increase revenue. The Strategic Plan consists of three core growth and value pillars that drive our business strategygrowth and the value of our business. We refer to generate more income from developed marketsthese three pillars as the growth and higher growth markets and businesses and (ii) enabling activitiesvalue pillars. In addition, the Strategic Plan includes certain initiatives that are designed to improve efficiency and leverage scale to increase our dividend and support the investmentgrowth and execution ofvalue pillars. We refer to these initiatives as the three

⁽¹⁾

"Developed Markets" include United States, Canada, western Europe and Australia.

⁽²⁾

"Emerging Markets" include central and eastern Europe, Latin America and the Asia Pacific region (excluding Australia).

⁽³⁾

"Adjacent Businesses" primarily include our data center and fine art storage businesses.

core pillars and maintain and strengthen our dividend.enabling activities. The Strategic Plan's growth and value pillars, as well as the enabling activities, are represented in the following graphic:

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        The table below highlights the significant 20152017 achievements with respect to each core growth and value pillar of our Strategic Plan:

Aligning Program Design with the Strategic Plan

        In connection with the continued execution of the Strategic Plan, theThe Compensation Committee periodically reviews our executive compensation programs to maintain the alignment of our incentives with our strategic objectives, including our Strategic Plan, and the creation of stockholder value. Our executive compensation programs include short-term and long-term incentive components.

        OurWe designed our short-term incentive program is designed to reward all of our executive officers for executing the Company's annual operating plan and demonstrating annual progress during the year toward the Company's achievement of multi-year strategic objectives. Results are measured on a constant currency

basis to remove the effects of foreign currency exchange rate fluctuations and measure achievement primarily within the control of management. Our short-term incentive program consists of two general criteria for evaluation:

•

evaluating the performance of our executive officers: (i) our financial performance (70% of short-term incentive opportunity): primarily rewards and (ii) the achievement of certain strategic objectives (30% of the short-term incentive opportunity).




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•

For the purposes of our short-term incentive program, we measure our financial performance against targets using revenue, Adjusted OIBDAEBITDA⁽⁴⁾ goals,, which is our primary measure of profit;profit, and adjusted funds from operations, or AFFO⁽⁵⁾, which measures our excess cash flows used primarily to reinvest in the business and increase returns to our stockholders through dividends. Our executive officers can earn additional short-term incentive awards may be earned for profitable revenue growth in excess of targets; andtargets.



•

strategic objectives (30%For the purposes of our short-term incentive opportunity): rewardsprogram, we measure the achievement during the year of certainstrategic objectives with respect to each core growth and value pillar of the Strategic Plan as well as other key initiatives related to real estate ownership, talentcapital efficiency, safety and safety.achievement of synergies. (For a description of these strategic objectives, see "Componentsthe "Compensation Discussion and Analysis—Components of Compensation—Short-Term Performance-Based Incentives—Strategic Objectives."Objectives" section of this Proxy Statement.)

        Our long-term incentive program rewards our success over a multi-year period relative to internal financial performance targets and stockholder returns through a portfolio of stock-basedstock based awards, including:

•

Storage Revenue PUs, which reward achievement of success in storage rental revenue growth objectives, subject to achieving a minimum level of return on invested capital, or ROIC.⁽⁵⁾⁽⁶⁾ Storage rental revenue growth is a key driver of cash flow, which in turn supports growth inof our dividend.dividends. Due, in part, to the three-year performance period of our Storage Revenue PUs, results are measured on a reported basis and includewithout regard to the effect of currency fluctuation;



•

Relative TSR PUs, or TSR-Based PUs, which reward total stockholder return, or TSR, performance, including the impact of changes in share price and reinvested dividends, which beginning in 2017 are measured relative to the MSCI US REIT Index over a three-year period (previously TSR was measured relative to the majority of the S&P 500 over a three-year period;500);



•

Stock Options,, which reward share price growth. Our stock optionsoption awards generally have an exercise price equal to the closing price of our Common Stock on the date of grant, or Fair Market Value of our stock at the date of grant, but our CEO's stock options have an exercise price 25% above the Fair Market Value at the date of grant. Stock options vest ratably over three years and are generally exercisable until the tenth anniversary of the grant date; and



•

Restricted Stock Units, or RSUs, which support retention and provide additional alignment with stockholders and vest ratably over three years.

        The Compensation Committee annually evaluates our incentive programs to ensure they continue to support our Strategic Plan and adopts changes where appropriate. In 2015 the Compensation

   

---

⁽⁴⁾

Adjusted OIBDAEBITDA is defined as income (loss) from continuing operations before interest expense, net, provision (benefit) for income taxes, depreciation and amortization, and also excludes certain items that we believe are not indicative of our core operating income before depreciation, amortization, intangible impairments,results, specifically: (i) loss (gain) loss on disposal/write-down of property, plant and equipment net (excluding real estate), Recall Costsnet; (ii) intangible impairments; (iii) other expense (income), net; (iv) gain on sale of real estate, net of tax; and REIT Costs. "Recall Costs" include operating expenditures associated with our proposed acquisition of Recall, including(v) costs to complete the Recall acquisition, including advisory and professional fees, as well as costs incurred to integrate Recall with our existing operations, including moving, severance, facility upgrade, REIT conversion and system upgrade costs. "REIT Costs" includecosts, as well as certain costs associated with our conversion to a REIT, excluding REIT compliance costs beginning January 1, 2014 which we expect to recur in future periods.shared service center initiative for our finance, human resources and information technology functions, or Recall Costs.



⁽⁵⁾

AFFO is defined as net income excluding depreciation on real estate assets, gain on sale of real estate, net of tax, loss (gain) on disposal/write-down of property, plant and equipment (excluding real estate), net, intangible impairments, other expense (income), net, Recall Costs, the tax impact of reconciling items and discrete tax items, loss (income) from discontinued operations, net of tax, loss (gain) on sale of discontinued operations, net of tax, non-cash rent expense or income, plus depreciation on non-real estate assets, amortization expense of customer relationship intangible assets, deferred financing costs and permanent withdrawal fees, stock-based compensation expense and the impact of reconciling to normalized cash taxes, less maintenance capital expenditures and non-real estate investments, excluding Recall integration capital expenditures.



⁽⁶⁾

ROIC is defined as net operating profit after taxes plus depreciation and amortization less non-growth capital expenditures divided by the average of the beginning and ending balance of total debt plus stockholders equity and non-controlling interest less cash plus accumulated depreciation on racking.




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Market Value. Stock option awards granted to our CEO from 2014 through 2016, however, have an exercise price 25% above the Fair Market Value at the date of grant. Stock options vest ratably over three years and are generally exercisable until the tenth anniversary of the grant date; and

•

RSUs, which support retention and provide additional alignment with stockholders and vest ratably over three years.

        The Compensation Committee annually evaluates our incentive programs to ensure they continue to support the Strategic Plan and adopts modifications where appropriate. In 2017, the Compensation Committee approved a series of refinements to better alignour 2017 incentive programs to strengthen alignment of our incentive programs with ourthe Strategic Plan, including:

•

refining the strategic measures contained in the short-term performance-based incentive program:



•

in our Developed Markets, we now utilize storage revenue internal growth, which reflects both volume growthselected innovation as an additional strategic measure focusing on the development and pricing,testing of new product concepts with a target of generating a new product offering that will contribute to measure achievement;the 2018 annual operating plan; and



•

we now consider a metric relatedachieved cost savings associated with the Transformation Initiative, in addition to the realization of certain security and safety related objectives toachieved synergies associated with Recall that was a strategic measure achievement; andin 2017.



•

implementing the second phase ofmodifying our long-term incentive, strategy, adoptedor LTI, program for our CEO and the PU structure for all recipients, which was further refined in 2014,2018, as discussed in the "Compensation Discussion and refined our performance metric to reflect our conversion to a real estate investment trust, or REIT:Analysis—2018 Updates" section of this Proxy Statement:



•

we granted TSR-Based PUsbegan two-year transition of our CEO LTI mix from one which included premium priced option to a broadmix consistent with executive vice presidents, or EVPs, using a multi-year approach to minimize the short-term changes;



•

changed the peer group of executives, including allfor measurement of our executive officers, consistent withRelative TSR PUs from the majority of the S&P 500 to the MSCI US REIT Index, which is the primary REIT index and an appropriate peer group in which to compare our long-term incentive strategy adopted in 2014;TSR performance; and



•

we changedmodified the revenue metric of certainpayout curve of our PU awardsStorage Revenue PUs to storage rental revenue from total revenue.align financial performance with payout levels in a manner that the Compensation Committee determined provide appropriate performance incentives and rewards for the performance targets.

20152017 Compensation Decisions &and Performance


Pay Opportunity

        Following its annual review of performance for 2016, executive development and relevant market benchmark data, the Compensation Committee approved increases in pay opportunity for certain of our Named Executive Officers, including our CEO. In each case, the majority (or, in the case of our CEO, the entirety) of the increase in pay




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opportunity was delivered through variable compensation,




which increased the proportion of compensation tied to achievement of performance goals or stock price appreciation.

Executive		Changes in Pay Opportunity		Considerations
William L. Meaney		• increased target bonus by 1015 percentage points to 135%150% of base salary • increased potential economic value of long-term incentive awards by $1,150,000$1,250,000 to $5,150,000$6,750,000		• reflects the Board's assessment of Mr. Meaney's performance and changes in relevant market benchmarks, which increased in part due to the effects of the Recall acquisition
				• 100% of the increased pay opportunity was delivered through variable compensation primarily long-term incentives • first increase in annual pay opportunity since joining the Company in 2013, which reflects the Board's assessment of Mr. Meaney's performance and increases to relevant market benchmarks
Roderick DayErnest Cloutier		• increased target bonus by 5 percentage points to 85% of base salary by 5% • increased potential economic value of long-term incentive awards by $250,000$50,000 to $1,250,000$750,000		• more than 90%reflects our CEO's assessment of Mr. Cloutier's performance and increased responsibility as a result of his transition into the role of EVP & GM, International • 100% of the increased pay opportunity was delivered through variable compensation primarily long-term incentives • reflects our CEO's assessment of Mr. Day's performance since his appointment in 2014 and his position relative to market benchmarks
Patrick Keddy		• increased base salary by 12%approximately 6% • increased target bonus by 105 percentage points to 70%85% of base salary • increased potential economic value of long-term incentive awards by $550,000$50,000 to $750,000$800,000		• more than 75% of the increased pay opportunity was delivered through variable compensation • reflects significantly increased responsibility in connection withour CEO's assessment of Mr. Keddy's appointmentperformance as EVP & GM, North America & Western Europe in April 2015and his position relative to market benchmarks

        Ms. Russo joined the Company March 13, 2017, and her pay opportunity is described in the "Compensation Discussion and Analysis—Chief Technology Officer" section of this Proxy Statement. No changes were made to Mr. Brown's pay opportunity for 2017.

Performance & Compensation Results

        Our short-term incentive awards reflect operational performance without regard to currency fluctuation, butIn 2017, our long-term incentive awards are measured on reported results.

        In 2015, our operationalfinancial performance, after adjusting for the impact of acquisitions and dispositions during the year and measured in constant currency, exceededand performance against strategic objectives, on average, achieved 100% of the goals on average, established by the Compensation Committee. Consequently, the pay-for-performance structure ofCommittee and our variable compensation programs delivered aboveexecutives exceeded expectations relative to their individual goals and objectives. Combining financial performance with individual performance, our target short-term incentive awards. On average, our short-term incentive awards achieved 119.35%115% of target; primarily as a result oftarget, on average, calculated based on the following operational results:

•

Adjusted OIBDA was 102.6%EBITDA and revenue achieved a combined payout of 100.85% of target reflecting our focus on continuous improvement and the early impact of the Transformation Program;due primarily to Adjusted EBITDA exceeding target levels;



•

enterprise revenueAFFO performance was 99.3%101.2% of target, reflecting improved internal growth; however, they were below the targets set by our Compensation Committee; andwhich resulted in a payout of 107.8% of target;



•

strategic objectives, on average, achieved 94%a combined payout of target performance with five92.5% of the six metrics meeting or exceeding target performance.target; and




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•

the Compensation Committee approved individual performance modifiers based on performance against individual goals and objectives that, on average, added 14% to the combined financial and strategic performance results discussed above.

        For 2017, our long-term incentive awards however,reflect operational performance without regard to currency fluctuation. However, certain of our performance units granted in 2015, which are measured on reported results, werecontinue to be negatively impacted by the strengtheningstrong U.S. dollar and the decline in our share price.dollar. As a result, long-term incentives, on average, are tracking significantly below the potential economic value at the time of their grant, which corresponds with the experience of our stockholders as measured over the same time period:grant:

•

our TSR during 20152017 was approximately –25.7%13% relative to 1.4%approximately 5% for the S&P 500 Total ReturnMSCI US REIT Index;



•

Mr. Meaney's 2013 TSR-Based PUs did not meetwith a performance period ending in 2017 earned 78.5% of target shares, reflecting performance during the minimum performance threshold ofrelevant period at the 30^th41st percentile of the S&P 500, excluding financial services companies, during the performance period and, as a result, no shares were earned under this award;companies; and



•

PUs based on Storage Revenue & ROIC performance for the various PUs awarded during 2014three-year period ending in 2017 earned 51.8% of target shares, reflecting performance between the target level and 2015, for which the performance periods have not been completed, are currently forecast, on average,minimum level, primarily due to pay significantly below the potential economic value at the time of their grant, which reflects the impact of share price decline, negative foreign currency impacts and revenue growth underperforming the goals set by the Compensation Committee, without regard to currency fluctuation.

Realizable Pay Analysis

        Realizable pay reflects actual bonuses earned and the current value of equity awards, which are subject to adjustment based on changes in our share price and the achievement of performance goals.        The Compensation Committee and the Company believe a realizable pay analysis with respect to our CEO is a valuable data point tohelps evaluate the pay-for-performancepay for performance effectiveness of our compensation programs and to evaluate the directional alignment of our equity awards with the experience of our stockholders.

        The realizable pay analysis compares realizable pay, or Realizable Pay, to pay opportunity, or Pay Opportunity, in the context of our operational performance and the performance of our Common Stock, where:

•

Pay Opportunity represents the target value of compensation awarded for each year and includes base salary, target bonus and the potential economic value of equity awards as measured at the date of grant; and



•

Realizable Pay represents the current value of Pay Opportunity adjusted for achievement relative to performance goals, changes to our share price through December 31, 2017 and the amount of dividends accrued on certain of our equity awards.

        The table below illustrates the relationship between the Pay Opportunity of our CEO for the five fiscal 2013, 2014 and 2015years ended 2017 and the realizable value of that compensationRealizable Pay measured at the end of 2015.2017. Over the three-yearfive year period ending onended December 31, 2015,2017, total Realizable Pay represents approximately 68%108% of




Pay Opportunity, primarily reflecting the underperformance, on average, of our PU awards, and the impact of our share price performance on other stock-basedpremium priced stock options,




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partially offset by the underperformance, on average, of our PU awards. All values below are shown in thousands.



Pay Opportunity—equals, for each of fiscal 2013, 2014, 2015, 2016 and 2015:2017: (1) annual base salary for the applicable fiscal year,plus (2) target bonus for the applicable fiscal year,plus (3) the potential economic value of equity awards approved during the applicable fiscal year by the Compensation Committee (as(in the case of each equity award, as measured at the date of grant). No target value is included forPay Opportunity does not include items reported in the "All Other Compensation" column of the "Compensation Tables—Summary Compensation Table.Table—Summary Compensation Table for 2015, 2016 and 2017" section of this Proxy Statement.

Realizable Pay—equals, for each of fiscal 2013, 2014, 2015, 2016 and 2015:2017: (1) annual base salary for the applicable fiscal year,plus (2) actual paid bonus for the applicable fiscal year,plus (3) in-the-moneyin the money value of stock options granted during the applicable year,plus (4) value of RSUs granted during the applicable fiscal year, including accrued dividends thereon,plus (5) value of PUs granted during the applicable fiscal year, reflecting actual achievement for awards granted in fiscal 2013, 2014 and 2015 and estimated performance as of the end of Fiscal 2015fiscal 2017 for awards granted in fiscal 20142016 and fiscal 20152017 (accordingly, the actual number of PUs that may be credited under these programs will vary). All equity values are calculated using the closing price of our Common Stock as of December 31, 2017.

2018 Updates


The company adopted changes in 2018 affecting our LTI Program and our CEO's pay opportunity. Certain of these changes are discussed below.

LTI Program Design

        Following an internal review of the Company's LTI design, the Compensation Committee approved a series of changes primarily intended to strengthen alignment of the LTI program's design with metrics that the Compensation Committee believes more accurately measure management's performance. The changes affect both the mix of LTI vehicles and the structure of PUs.




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LTI Mix—the Compensation Committee approved two changes to the LTI mix for EVPs:

Vehicle		2017		2018
PUs Stock Options RSUs		50% 20% 15%		55% 30% 30%		• stock option portion reduced from 20% to 15%, primarily to manage share usage due to the dilutive nature of stock options • PU portion increased from 50% to 55%, maintaining the focus on performance-based LTI (stock options and PUs)

PU Design—The Compensation Committee approved changes intended to increase focus on elements that more accurately measure management performance:

•

performance metrics include total revenue and Adjusted EBITDA growth over a three-year period to reward performance of recipients for top-line growth and bottom-line efficiency; and



•

the portion of PUs tied to internal financial metrics was increased from 50% to 75% to align PU payouts more closely with elements that more accurately measure management performance.

Chief Executive Officer Pay Opportunity

        In connection with its annual compensation program review, the Board approved an increase to Mr. Meaney's pay opportunity for 2018.

Item		Changes in Pay Opportunity		Considerations
Pay Opportunity		• increased annual base salary by 10%, the first increase since joining the Company in 2013 • increased potential economic value of long-term incentive awards by $1,500,000 to $8,250,000		• the increase in annual base salary and long-term incentives reflects the Board's assessment of Mr. Meaney's performance and increases in relevant market benchmarks • 94% of the increased pay opportunity was delivered through variable compensation
LTI Mix		• completed the second step in the two-year transition of our CEO LTI mix to a mix consistent with our EVPs (as described in the LTI Program Design section immediately above)		• strengthens alignment of LTI program design with Company performance

Say-on-Pay Vote Response and Stockholder Engagement


        We have an annual stockholder advisory vote on executive compensation, a "say-on-pay" vote, to provide stockholders with an additional tool to voice their opinions about executive compensation, with a goal of maintaining an alignment of interests between our stockholders and our executives. The Compensation Committee considered the results of the advisory vote by stockholders on the "say-on-pay" proposal presented to stockholders at the Company's 20152017 Annual Meeting of Stockholders. As in previous years, there was overwhelming support at the 20152017 annual meeting for the compensation program offered to the Company's Named Executive Officers, with approximately 98%97% of votes cast in favor.favor of our compensation program. Accordingly, in 2015,2017, the Compensation Committee made no direct changes to the Company's executive compensation programs as a result of the say-on-pay vote at the Company's 20152017 Annual Meeting of Stockholders.




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        In March 2018, the Company's management conducted outreach with certain stockholders related to our executive compensation. Even though we have received significant support from stockholders through our say-on-pay votes, the Company and the Compensation Committee believes it is important to periodically engage directly with our stockholders in order to gain a better understanding of our stockholders' views on our executive compensation practices. We contacted 12 stockholders that, collectively, held approximately 56% of our outstanding Common Stock, and ultimately we communicated with seven stockholders that, collectively, held approximately 31% of our outstanding Common Stock. The stockholders with whom we communicated reiterated their support for our approach to executive compensation while sharing their perspective on what they most value in executive compensation programs. The findings will be reported to and will be considered by the Compensation Committee in connection with its annual review of our incentive plans.

        Our executive compensation programs reflect a number of best practices, implemented by the Compensation Committee in recent years, including:

•

compensation clawback policy;






•

executive and director stock ownership requirements, which exclude unvested and unearned shares, including a requirement to retain certain50% of after-tax shares until the requirement is met;



•

between 71%72% and 87%89% of the target direct compensation for our Named Executive Officers' target direct compensationOfficers is at-risk;



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"double trigger" feature, requiring both a change in control and termination of employment before the acceleration of vesting of awards granted under both the 2002 Plan and the 2014 Plan;



•

a prohibition on hedging or pledging of shares of Common Stock;



•

the Compensation Committee retains an independent compensation consultant;



•

we do not offer excise tax gross-ups in connection with a change in control;



•

we do not offer pensions or supplemental executive retirement plans; and



•

limited use of executive perquisites that recognize standard local practices in international markets.

        In early 2016, the Company's management conducted outreach with certain stockholders related to our executive compensation. Even though we have received significant support from stockholders through our say-on-pay votes, the Company and the Compensation Committee believes it is important to periodically engage directly with our stockholders in order to gain a better understanding of our stockholders' views on our executive compensation practices. We ultimately engaged with stockholders representing 35% of our outstanding shares of Common Stock, and the stockholders with whom we communicated reiterated their support for our approach to executive compensation while sharing their perspective on what they most value in executive compensation programs. The findings were reported to and considered by the Compensation Committee in connection with its annual review of our incentive plans.

Compensation Philosophy and Design Principles


        The purpose of our executive compensation programs is to attract, retain and focus the talents and energies of executives,our Executive Officers, including our Named Executive Officers, on meeting the current and future objectives of the Company, most notably the creation of stockholder value. The design principles that govern our Named Executive Officer compensation programs are described below.

        General program competitiveness—Our compensation program servesprograms serve to attract and retain top performing executive officers. All of our executive compensation programs target pay levels are established with reference to relevant market data to evaluate their competitiveness.data. The relative position of each Named Executive Officer's compensation compared to the market data referenced reflects his or her experience and proficiency in performing the duties of his or her position.

        Pay for performance—A substantial percentage of each Named Executive Officer's total compensation opportunity is contingent on annual and multi-year performance, as discussed above under the heading "Aligning Program Design with the Strategic Plan." If performance exceeds the target, then an award can pay out in excess of the target value. Conversely, if performance does not achieve the target, compensationan award can fallpay out below an award'sthe target levelvalue and, in fact, be as low as zero.




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        Internal parity—The total compensation opportunity for each Named Executive Officer reflects the responsibility, scope and complexity of that individual's role within the Company.

        Stockholder alignment—Our compensation programs for our Named Executive Officers align with the interests of our stockholders by emphasizingrewarding performance criteria that drivedrives both short-term results and long-term stockholder value creation. Our Named Executive Officers, includingEVPs and our CEO, are also subject to minimum share ownership requirements, as discussed under the "Executive"Compensation Discussion and Analysis—Components of Compensation—Long-Term Equity Compensation—Executive Stock Ownership Guidelines" section of this Proxy Statement.




        Alignment with various business strategies—Beginning in 2014, we structured our executive compensation programs primarily to provide common rewards forreward the achievement of enterprise financial goals and strategic objectives. Our annual short-term incentive program continues to provide for individual differentiation reflectingthat reflects each executive's responsibility for the individual performance of suchand the contribution to the executive's function's or business unit's contributionunit toward the commonenterprise goals, and such executive's bonus may be adjusted according to achievement versusmeasured against individual objectives.

Establishing Compensation


Process

        In applying our compensation philosophy and design principles to establish appropriate compensation programs and target compensation levels, the Compensation Committee:

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Annuallyannually approves a recommendation to the Board for the salary, short-term and long-term incentive compensation for our CEO. The Compensation Committee's recommendation reflects (1) an analysis of the Company's performance against predetermined financial goals and its evaluation of our CEO's performance against predetermined individual objectives, (2) performance feedback from our CEO's direct reports, which is also shared with other members of the Board, and (3) input from members of the Board. The Compensation Committee's recommendation is then presented to the independent members of the Board for approval.approval;



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Annuallyannually reviews and approves the salary, short-term and long-term incentive compensation for our other Named Executive Officers.Officers;



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Annuallyannually reviews and approves the structure of our short-term and long-term incentive programs for all Named Executive Officers, including performance metrics, performance and payout grids and the weighting applied to each metric. The review typically balances an internal and external perspective developed in collaboration with members of management and the Compensation Committee's independent compensation consultant. Based upon this review, the Compensation Committee may maintain or modify the amount and mix of grants under our incentive programs.programs;



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Annuallyannually establishes the individual goals and objectives utilized in our short-term incentive program for our CEO and reviews the individual goals for theour other Named Executive Officers recommended by our CEO.CEO;



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Periodicallyperiodically evaluates the effectiveness and competitiveness of other executive compensation programs, such as executive benefits, perquisites and our severance policies. These periodic evaluations are conducted to ensure alignment with our internal strategy and objectives and to consider external market practices.practices; and



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Annuallyannually establishes the financial performance goals that are utilized in our short-term and long-term incentive plans. The annual financial performance targets are initially based upon our annual operating plan approved by the Board, assuming constant currency, and may be adjusted during the year. The multi-year performance targets are aligned with achieving our Strategic Plan. When




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the financial targets are set, the Compensation Committee approves a policy which identifiesseries of adjustment factors that identify the nature of potential adjustments to the target levels that may be considered throughout the fiscal year. Our internal audit team reviews the potential adjustments and reports the results to our AuditCompensation Committee. The Compensation Committee considers these reports and may adjust financial targets based on the adjustment factors approved at the beginning of the year.

        In 2015,2017, the Compensation Committee approved adjustments to performance goal targets, or the Adjustment Factors, to (1) eliminate the effects of unbudgeted acquisitions and dispositions, (2) eliminate the effects of

75th percentiles of relevant market data as one frame of reference in making its compensation decisions. Final compensation decisions reflect a variety of factors, including each executive's experience, performance rating, the relative importance of the executive's role within the organization, as well as where each executive's pay level falls relative to the market data.

        Plan design—When designing or assessing the design of our compensation programs, the Compensation Committee reviews programs of the Custom Peer Group to establish typical market practice. The Compensation Committee evaluates our specific circumstances and business objectives and follows market practice with respect to the design of our programs where appropriate but may deviate from market practice where the Compensation Committee deems it is in the best interest of the Company and ourits stockholders.

Components of 2017 Compensation

Role of ConsultantsOverview

        The Compensation Committee has retained the services of an independent compensation consultant to provide ongoing advice and perspective to the Compensation Committee in the following areas related to the compensation of our Named Executive Officers:

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market pay analyses and market trends;



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assistance with the review and selection of the Custom Peer Group;



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ongoing support with regard to the latest relevant regulatory, technical and/or accounting considerations affecting compensation and benefit programs;



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assistance with the design of executive compensation or benefit programs, as needed; and



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preparation for and attendance at selected Compensation Committee meetings.

        Since May 2012, the Compensation Committee has engaged Pay Governance LLC, or Pay Governance, to assist the Compensation Committee by providing ongoing executive compensation consulting. Pay Governance reports directly to the Compensation Committee and has regular meetings with the chairperson of the Compensation Committee.

        Pay Governance does not provide any other services to the Company except providing assistance on director compensation matters for the Nominating and Governance Committee. The Compensation Committee has reviewed the nature of the relationship with its independent compensation consultants and determined that there were no conflicts that impacted the advice and guidance provided to the Compensation Committee.

Components of Compensation

        Our Named Executive Officers' total direct compensation, or TDC, for our Executive Officers is designed to reward our Named Executive Officersthem based on achievement of financial and strategic goals and returns to stockholders andstockholders. TDC consists of base salary, target bonus and long-term incentive grant value.

        As depicted below, approximately 87%89% of our CEO's target TDC, and, on average, 71%72% of the target TDC of our other Named Executive Officers' target TDCOfficers (where applicable, excluding the value of new hire inducement equity awards), is tied directly to the achievement of financial goals, strategic objectives or stock price appreciation through our short-term and long-term incentive programs.

CEO		Other Named Executive Officers

        Below is a summary of the elements, objectives, risk mitigation factors and key features of our TDC program for our Named Executive Officers. A more detailed discussion of each element and the associated pay decisions follows this section.

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Base salary and benefits are designed to attract and retain highly qualified individuals; in order to avoid excessive risk taking, it is important that not all cash compensation be variable.



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Annual cash short-term incentive compensation awards are designed to focus the entire senior executive team, including the Namedall Executive Officers toward achieving enterprise goals while recognizing their individual contributions, including:



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attaining financial goals in line with our annual budget;



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achievement ofachieving strategic objectives;



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performanceperforming relative to initiatives in areas within their control; and