SC 13D/A

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

(Rule 13d-101)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

TO § 240.13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO

§ 240.13d-2(a)

(Amendment No. 2)1

Quantum Corporation

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

747906204

(CUSIP Number)

JEFFREY C. SMITH

STARBOARD VALUE LP

830 Third Avenue, 3rd Floor

New York, New York 10022

(212) 845-7977

STEVE WOLOSKY, ESQ.

OLSHAN FROME WOLOSKY LLP

Park Avenue Tower

65 East 55th Street

New York, New York 10022

(212) 451-2300

(Name, Address and Telephone Number of Person

Authorized to Receive Notices and Communications)

May 13, 2013

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box ¨.

Note:  Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits.  See § 240.13d-7 for other parties to whom copies are to be sent.

_______________

1              The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP NO. 747906204

1	NAME OF REPORTING PERSON STARBOARD VALUE AND OPPORTUNITY MASTER FUND LTD
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) o   (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS WC
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION CAYMAN ISLANDS
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER 26,128,823*
	8	SHARED VOTING POWER - 0 -
	9	SOLE DISPOSITIVE POWER 26,128,823*
	10	SHARED DISPOSITIVE POWER - 0 -
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 26,128,823*
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 10.3%
14	TYPE OF REPORTING PERSON CO

* Includes Shares underlying certain convertible senior subordinated notes.

2

CUSIP NO. 747906204

1	NAME OF REPORTING PERSON STARBOARD VALUE AND OPPORTUNITY S LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) o   (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS WC
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER 5,862,924*
	8	SHARED VOTING POWER - 0 -
	9	SOLE DISPOSITIVE POWER 5,862,924*
	10	SHARED DISPOSITIVE POWER - 0 -
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,862,924*
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 2.4%
14	TYPE OF REPORTING PERSON OO

* Includes Shares underlying certain convertible senior subordinated notes.

3

CUSIP NO. 747906204

1	NAME OF REPORTING PERSON STARBOARD VALUE AND OPPORTUNITY C LP
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) o   (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS WC
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER 3,008,940*
	8	SHARED VOTING POWER - 0 -
	9	SOLE DISPOSITIVE POWER 3,008,940*
	10	SHARED DISPOSITIVE POWER - 0 -
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 3,008,940*
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 1.2%
14	TYPE OF REPORTING PERSON PN

* Includes Shares underlying certain convertible senior subordinated notes.

4

CUSIP NO. 747906204

1	NAME OF REPORTING PERSON STARBOARD VALUE R LP
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) o   (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS OO
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER 3,008,940*
	8	SHARED VOTING POWER - 0 -
	9	SOLE DISPOSITIVE POWER 3,008,940*
	10	SHARED DISPOSITIVE POWER - 0 -
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 3,008,940*
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 1.2%
14	TYPE OF REPORTING PERSON PN

* Includes Shares underlying certain convertible senior subordinated notes.

5

CUSIP NO. 747906204

1	NAME OF REPORTING PERSON STARBOARD VALUE R GP LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) o   (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS OO
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER 3,008,940*
	8	SHARED VOTING POWER - 0 -
	9	SOLE DISPOSITIVE POWER 3,008,940*
	10	SHARED DISPOSITIVE POWER - 0 -
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 3,008,940*
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 1.2%
14	TYPE OF REPORTING PERSON OO

* Includes Shares underlying certain convertible senior subordinated notes.

6

CUSIP NO. 747906204

1	NAME OF REPORTING PERSON STARBOARD VALUE LP
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) o   (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS OO
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER 44,243,875*
	8	SHARED VOTING POWER - 0 -
	9	SOLE DISPOSITIVE POWER 44,243,875*
	10	SHARED DISPOSITIVE POWER - 0 -
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 44,243,875*
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 17.0%
14	TYPE OF REPORTING PERSON PN

* Includes Shares underlying certain convertible senior subordinated notes.

7

CUSIP NO. 747906204

1	NAME OF REPORTING PERSON STARBOARD VALUE GP LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) o   (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS OO
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER 44,243,875*
	8	SHARED VOTING POWER - 0 -
	9	SOLE DISPOSITIVE POWER 44,243,875*
	10	SHARED DISPOSITIVE POWER - 0 -
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 44,243,875*
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 17.0%
14	TYPE OF REPORTING PERSON OO

* Includes Shares underlying certain convertible senior subordinated notes.

8

CUSIP NO. 747906204

1	NAME OF REPORTING PERSON STARBOARD PRINCIPAL CO LP
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) o   (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS OO
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER 44,243,875*
	8	SHARED VOTING POWER - 0 -
	9	SOLE DISPOSITIVE POWER 44,243,875*
	10	SHARED DISPOSITIVE POWER - 0 -
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 44,243,875*
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 17.0%
14	TYPE OF REPORTING PERSON PN

* Includes Shares underlying certain convertible senior subordinated notes.

9

CUSIP NO. 747906204

1	NAME OF REPORTING PERSON STARBOARD PRINCIPAL CO GP LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) o   (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS OO
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER 44,243,875*
	8	SHARED VOTING POWER - 0 -
	9	SOLE DISPOSITIVE POWER 44,243,875*
	10	SHARED DISPOSITIVE POWER - 0 -
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 44,243,875*
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 17.0%
14	TYPE OF REPORTING PERSON OO

* Includes Shares underlying certain convertible senior subordinated notes.

10

CUSIP NO. 747906204

1	NAME OF REPORTING PERSON JEFFREY C. SMITH
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) o   (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS OO
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION USA
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER - 0 -
	8	SHARED VOTING POWER 44,243,875*
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 44,243,875*
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 44,243,875*
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 17.0%
14	TYPE OF REPORTING PERSON IN

* Includes Shares underlying certain convertible senior subordinated notes.

11

CUSIP NO. 747906204

1	NAME OF REPORTING PERSON MARK R. MITCHELL
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) o   (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS OO
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION USA
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER - 0 -
	8	SHARED VOTING POWER 44,243,875*
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 44,243,875*
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 44,243,875*
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 17.0%
14	TYPE OF REPORTING PERSON IN

* Includes Shares underlying certain convertible senior subordinated notes.

12

CUSIP NO. 747906204

1	NAME OF REPORTING PERSON PETER A. FELD
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) o   (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS OO
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION USA
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER - 0 -
	8	SHARED VOTING POWER 44,243,875*
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 44,243,875*
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 44,243,875*
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 17.0%
14	TYPE OF REPORTING PERSON IN

* Includes Shares underlying certain convertible senior subordinated notes.

13

CUSIP NO. 747906204

The following constitutes Amendment No. 2 to the Schedule 13D filed by the undersigned (“Amendment No. 2”).  This Amendment No. 2 amends the Schedule 13D as specifically set forth herein.

Item 2. Identity and Background.

Item 2 is hereby amended and restated as follows:

(a)           This statement is filed by:

(i) Starboard Value and Opportunity Master Fund Ltd, a Cayman Islands exempted company (“Starboard V&O Fund”), with respect to the Shares directly and beneficially owned by it;

(ii) Starboard Value and Opportunity S LLC, a Delaware limited liability company (“Starboard LLC”), with respect to the Shares directly and beneficially owned by it;

(iii) Starboard Value and Opportunity C LP, a Delaware limited partnership (“Starboard C LP”), with respect to the Shares directly and beneficially owned by it;

(iv) Starboard Value LP (“Starboard Value LP”), as the investment manager of Starboard V&O Fund, Starboard C LP and of a certain managed account (the “Starboard Value LP Account”) and the manager of Starboard LLC;

(v) Starboard Value GP LLC (“Starboard Value GP”), as the general partner of Starboard Value LP;

(vi) Starboard Principal Co LP (“Principal Co”), as a member of Starboard Value GP;

(vii) Starboard Principal Co GP LLC (“Principal GP”), as the general partner of Principal Co;

(viii) Starboard Value R LP (“Starboard R LP”), as the general partner of Starboard C LP;

(ix) Starboard Value R GP LLC (“Starboard R GP”), as the general partner of Starboard R LP;

(x) Jeffrey C. Smith, as a member of Principal GP and as a member of each of the Management Committee of Starboard Value GP and the Management Committee of Principal GP;

(xi) Mark R. Mitchell, as a member of Principal GP and as a member of each of the Management Committee of Starboard Value GP and the Management Committee of Principal GP; and

(xii) Peter A. Feld, as a member of Principal GP and as a member of each of the Management Committee of Starboard Value GP and the Management Committee of Principal GP.

14

CUSIP NO. 747906204

Each of the foregoing is referred to as a “Reporting Person” and collectively as the “Reporting Persons.”  Each of the Reporting Persons is party to that certain Joint Filing Agreement, as further described in Item 6.  Accordingly, the Reporting Persons are hereby filing a joint Schedule 13D.

(b)           The address of the principal office of each of Starboard LLC, Starboard C LP, Starboard Value LP, Starboard Value GP, Principal Co, Principal GP, Starboard R LP, Starboard R GP, and Messrs. Smith, Mitchell and Feld is 830 Third Avenue, 3rd Floor, New York, New York 10022.  The address of the principal office of Starboard V&O Fund is 89 Nexus Way, Camana Bay, PO Box 31106, Grand Cayman KY1-1205, Cayman Islands.  The officers and directors of Starboard V&O Fund and their principal occupations and business addresses are set forth on Schedule A to the Schedule 13D and are incorporated by reference in this Item 2.

(c)           The principal business of Starboard V&O Fund is serving as a private investment fund.  Starboard V&O Fund has been formed for the purpose of making equity investments and, on occasion, taking an active role in the management of portfolio companies in order to enhance shareholder value.  Starboard LLC and Starboard C LP have been formed for the purpose of investing in securities and engaging in all related activities and transactions.  Starboard Value LP provides investment advisory and management services and acts as the investment manager of Starboard V&O Fund, Starboard C LP and the Starboard Value LP Account and the manager of Starboard LLC.  The principal business of Starboard Value GP is providing a full range of investment advisory, pension advisory and management services and serving as the general partner of Starboard Value LP.  The principal business of Principal Co is providing investment advisory and management services.  Principal Co is a member of Starboard Value GP.  Principal GP serves as the general partner of Principal Co.  Starboard R LP serves as the general partner of Starboard C LP. Starboard R GP serves as the general partner of Starboard R LP.  Messrs. Smith, Mitchell and Feld serve as members of Principal GP and the members of each of the Management Committee of Starboard Value GP and the Management Committee of Principal GP.

(d)           No Reporting Person, nor any person listed on Schedule A to the Schedule 13D, annexed hereto, has, during the last five years, been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors).

(e)           No Reporting Person, nor any person listed on Schedule A to the Schedule 13D, has, during the last five years, been party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

(f)           Messrs. Smith, Mitchell and Feld are citizens of the United States of America.  The citizenship of the persons listed on Schedule A to the Schedule 13D is set forth therein.

Item 3. Source and Amount of Funds or Other Consideration.

Item 3 is hereby amended and restated as follows:

The Shares purchased by each of Starboard V&O Fund, Starboard LLC and Starboard C LP and held in the Starboard Value LP Account were purchased with working capital (which may, at any given time, include margin loans made by brokerage firms in the ordinary course of business) in open market purchases, except as otherwise noted, as set forth in Schedule A, which is incorporated by reference herein.  The aggregate purchase price of the 26,128,823 Shares beneficially owned by Starboard V&O Fund is approximately $38,354,507, excluding brokerage commissions.  Such aggregate purchase price includes $18,960,000, which is the purchase price of $18,960,000 principal amount of Notes (as defined in the Schedule 13D) convertible into 11,511,839 Shares.  The aggregate purchase price of the 5,862,924 Shares beneficially owned by Starboard LLC is approximately $8,606,755, excluding brokerage commissions.  Such aggregate purchase price includes $4,260,000, which is the purchase price of $4,260,000 principal amount of Notes convertible into 2,586,521 Shares.  The aggregate purchase price of the 3,008,940 Shares beneficially owned by Starboard C LP is approximately $3,867,186, excluding brokerage commissions.  Such aggregate purchase price includes $565,788, which is the purchase price of $550,000 principal amount of the Notes convertible into 333,940 Shares.  The aggregate purchase price of the 9,243,188 Shares held in the Starboard Value LP Account is approximately $13,579,188, excluding brokerage commissions.  Such aggregate purchase price includes $6,780,000, which is the purchase price of $6,780,000 principal amount of Notes convertible into 4,116,575 Shares.

15

CUSIP NO. 747906204

Item 4. Purpose of Transaction.

Item 4 is hereby amended to add the following:

On May 13, 2013, Starboard (as defined in the Settlement Agreement) and the Issuer entered into a settlement agreement (the “Settlement Agreement”). The following description of the Settlement Agreement is qualified in its entirety by reference to the Settlement Agreement, which is attached as Exhibit 99.1 hereto and is incorporated herein by reference.

Pursuant to the terms of the Settlement Agreement, the Issuer agreed, among other things: (i) to immediately increase the size of the Board of Directors of the Issuer (the “Board”) from eight (8) to nine (9) members; (ii) to appoint Jeffrey Smith to the Board immediately; (iii) to nominate and solicit proxies for the election of Louis DiNardo and Philip Black (together with Messrs. DiNardo and Smith, the “Starboard Nominees”) to the Board at the 2013 annual meeting of stockholders of the Issuer (the “2013 Annual Meeting”); (iv) in the interim, to appoint Messrs. DiNardo and Black as observers to the Board, subject to attorney-client privilege and their execution of a confidentiality agreement; (v) promptly following the date of the Settlement Agreement, but no later than 30 days from such date, to appoint Mr. Smith to the Leadership and Compensation Committee of the Board; and (vi) promptly following the conclusion of the 2013 Annual Meeting, but no later than 30 days thereafter, to appoint Mr. DiNardo as chairman of the Governance Committee of the Board and appoint Mr. Black to the Audit Committee of the Board.  If any Starboard Nominee is unable to serve as a director, resigns or is removed as a director prior to the 2014 annual meeting of stockholders of the Issuer (the “2014 Annual Meeting”) and at such time Starboard beneficially owns in the aggregate, excluding Shares underlying the Notes, at least three percent (3.0%) of the Issuer’s then outstanding Shares, then Starboard can recommend substitute person(s) who meet certain independence and experience criteriafor approval by the Corporate Governance and Nominating Committee of the Board and appointment by the Board within five (5) business days after such committee’s approval.

The Issuer further agreed not to increase the size of the Board to more than nine (9) directors during the Standstill Period (as defined in the Settlement Agreement) and to use its reasonable best efforts to hold the 2013 Annual Meeting no later than September 15, 2013.

Pursuant to the terms of the Settlement Agreement, Starboard agreed, among other things: (i) not to nominate any person for election at the 2013 Annual Meeting; (ii) not to submit any proposal for consideration at, or bring any other business before, the 2013 Annual Meeting, directly or indirectly; (iii) not to initiate, encourage or participate in any “withhold” or similar campaign with respect to the 2013 Annual Meeting, directly or indirectly; (iv) to appear in person or by proxy at the 2013 Annual Meeting and vote all Shares beneficially owned by it in favor of the election of each of the Issuer’s nominees for election to the Board and in accordance with the Board’s recommendation with respect to the Issuer’s “say-on-pay” proposal, unless Institutional Shareholder Services Inc. recommends otherwise; and (v) to obtain an irrevocable resignation letter from Mr. Smith pursuant to which he will resign from the Board and all applicable committees thereof if at any time during the Standstill Period Starboard’s aggregate beneficial ownership of the Shares, excluding Shares underlying the Notes, decreases to less than three percent (3.0%) of the Issuer’s then outstanding Shares.

16

CUSIP NO. 747906204

In addition, Starboard agreed, from the date of the Settlement Agreement through the earlier of (a) fifteen (15) business days prior to the deadline for the submission of stockholder nominations for the  2014 Annual Meeting and (b) one-hundred (100) days prior to the first anniversary of the 2013 Annual Meeting, not to, directly or indirectly, in any manner: (i) engage in any solicitation of proxies or consents or become a “participant” in a “solicitation” as such terms are defined in Regulation 14A under the Securities Exchange Act of 1934, as amended (the “Exchange Act”) of proxies or consents; (ii) form, join or in any way participate in any “group” (within the meaning of Section 13(d)(3) of the Exchange Act) with respect to the Shares;  (iii) deposit any Shares in any voting trust or subject any Shares to any arrangement or agreement with respect to the voting of any Shares, other than any such voting trust, arrangement or agreement solely among the members of Starboard; (iv) seek or encourage any person to submit nominations in furtherance of a “contested solicitation,” or take other action,  for the election or removal of directors with respect to the Issuer; (v) (A) make any proposal for consideration by stockholders at any annual or special meeting of stockholders of the Issuer, (B) make any offer or proposal with respect to a merger, acquisition, recapitalization, restructuring, disposition or other business combination involving the Issuer, or encourage, initiate or support any other third party in any such related activity or (C) make any public communication in opposition to any Issuer acquisition or disposition activity approved by the Board; (vi) seek, alone or in concert with others, representation on the Board; (vii) seek to advise, encourage, support or influence any person with respect to the voting or disposition of any securities of the Issuer at any annual or special meeting of stockholders; or (viii) make any request or submit any proposal to amend the terms of the Settlement Agreement other than through non-public communications with the Issuer that would not be reasonably determined to trigger public disclosure obligations for Starboard or the Issuer.

On May 14, 2013, the Issuer and Starboard jointly issued a mutually agreeable press release to announce they have reached a Settlement Agreement.

Item 5. Interest in Securities of the Issuer.

Items 5(a)-(c) are hereby amended and restated to read as follows:

The aggregate percentage of Shares reported owned by each person named herein is calculated using as the numerator the respective Shares held by each Reporting Person, including Shares issuable upon conversion of the Notes, and as the denominator 240,962,472 Shares outstanding, as of February 1, 2013, which is the total number of Shares outstanding as reported in the Issuer’s Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on February 8, 2013, plus the number of Shares issuable upon conversion of the Notes held by such Reporting Person.

A. Starboard V&O Fund

(a) As of the close of business on May 14, 2013, Starboard V&O Fund beneficially owned 26,128,823Shares, including 11,511,839 Shares underlying the Notes.

Percentage: Approximately 10.3%

17

CUSIP NO. 747906204

(b) 1. Sole power to vote or direct vote: 26,128,823

2. Shared power to vote or direct vote: 0

3. Sole power to dispose or direct the disposition: 26,128,823

4. Shared power to dispose or direct the disposition: 0

(c) Starboard V&O Fund has not entered into any transactions in the Shares during the past sixty days.

B. Starboard LLC

(a) As of the close of business on May 14, 2013, Starboard LLC beneficially owned 5,862,924Shares, including 2,586,521 Shares underlying the Notes.

Percentage: Approximately 2.4%

(b) 1. Sole power to vote or direct vote: 5,862,924

2. Shared power to vote or direct vote: 0

3. Sole power to dispose or direct the disposition: 5,862,924

4. Shared power to dispose or direct the disposition: 0

(c) Starboard LLC has not entered into any transactions in the Shares during the past sixty days.

C. Starboard C LP

(a) As of the close of business on May 14, 2013, Starboard C LP beneficially owned 3,008,940 Shares, including 333,940 Shares underlying the Notes.

Percentage: Approximately 1.2%

(b) 1. Sole power to vote or direct vote: 3,008,940

2. Shared power to vote or direct vote:  0

3. Sole power to dispose or direct the disposition: 3,008,940

4. Shared power to dispose or direct the disposition: 0

(c) The transactions in the Shares by Starboard C LP during the past sixty days are set forth in Schedule A and are incorporated herein by reference.

D. Starboard R LP

(a) Starboard R LP, as the general partner of Starboard C LP, may be deemed the beneficial owner of the 3,008,940 shares owned by Starboard C LP.

Percentage: Approximately 1.2%

(b) 1. Sole power to vote or direct vote: 3,008,940

2. Shared power to vote or direct vote: 0

3. Sole power to dispose or direct the disposition: 3,008,940

4. Shared power to dispose or direct the disposition: 0

(c) Starboard R LP has not entered into any transactions in the Shares during the past sixty days.  The transactions in the Shares on behalf of Starboard C LP during the past sixty days are set forth in Schedule A and are incorporated herein by reference.

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E.           Starboard R GP

(a) Starboard R GP, as the general partner of Starboard R LP, may be deemed the beneficial owner of the 3,008,940 shares owned by Starboard C LP.

Percentage: Approximately 1.2%

(b) 1. Sole power to vote or direct vote: 3,008,940

2. Shared power to vote or direct vote: 0

3. Sole power to dispose or direct the disposition: 3,008,940

4. Shared power to dispose or direct the disposition: 0

(c) Starboard R GP has not entered into any transactions in the Shares during the past sixty days.  The transactions in the Shares on behalf of Starboard C LP during the past sixty days are set forth in Schedule A and are incorporated herein by reference.

F. Starboard Value LP

(a) As of the close of business on May 14, 2013, 9,243,188 Shares were held in the Starboard Value LP Account, including 4,116,575 Shares underlying the Notes.  Starboard Value LP, as the investment manager of Starboard V&O Fund, Starboard C LP and the Starboard Value Account and the manager of Starboard LLC, may be deemed the beneficial owner of the (i) 26,128,823Shares owned by Starboard V&O Fund, (ii) 5,862,924 Shares owned by Starboard LLC, (iii) 3,008,940 Shares owned by Starboard C LP and (iv) 9,243,188 Shares held in the Starboard Value LP Account.

Percentage: Approximately 17.0%

(b) 1. Sole power to vote or direct vote: 44,243,875

2. Shared power to vote or direct vote: 0

3. Sole power to dispose or direct the disposition: 44,243,875

4. Shared power to dispose or direct the disposition: 0

(c) Starboard Value LP has not entered into any transactions in the Shares during the past sixty days. The transactions in the Shares on behalf of Starboard C LP during the past sixty days are set forth in Schedule A and are incorporated herein by reference.

G. Starboard Value GP

(a) Starboard Value GP, as the general partner of Starboard Value LP, may be deemed the beneficial owner of the (i) 26,128,823Shares owned by Starboard V&O Fund, (ii) 5,862,924 Shares owned by Starboard LLC, (iii) 3,008,940 Shares owned by Starboard C LP and (iv) 9,243,188 Shares held in the Starboard Value LP Account.

Percentage: Approximately 17.0%

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CUSIP NO. 747906204

(b) 1. Sole power to vote or direct vote: 44,243,875

2. Shared power to vote or direct vote: 0

3. Sole power to dispose or direct the disposition: 44,243,875

4. Shared power to dispose or direct the disposition: 0

(c) Starboard Value GP has not entered into any transactions in the Shares during the past sixty days.  The transactions in the Shares on behalf of Starboard C LP during the past sixty days are set forth in Schedule A and are incorporated herein by reference.

H. Principal Co

(a) Principal Co, as a member of Starboard Value GP, may be deemed the beneficial owner of the (i) 26,128,823 Shares owned by Starboard V&O Fund, (ii) 5,862,924 Shares owned by Starboard LLC, (iii) 3,008,940 Shares owned by Starboard C LP and (iv) 9,243,188 Shares held in the Starboard Value LP Account.

Percentage: Approximately 17.0%

(b) 1. Sole power to vote or direct vote: 44,243,875

2. Shared power to vote or direct vote: 0

3. Sole power to dispose or direct the disposition: 44,243,875

4. Shared power to dispose or direct the disposition: 0

(c) Principal Co has not entered into any transactions in the Shares during the past sixty days.  The transactions in the Shares on behalf of Starboard C LP during the past sixty days are set forth in Schedule A and are incorporated herein by reference.

I. Principal GP

(a) Principal GP, as the general partner of Principal Co, may be deemed the beneficial owner of the (i) 26,128,823Shares owned by Starboard V&O Fund, (ii) 5,862,924 Shares owned by Starboard LLC, (iii) 3,008,940 Shares owned by Starboard C LP and (iv) 9,243,188 Shares held in the Starboard Value LP Account.

Percentage: Approximately 17.0%

(b) 1. Sole power to vote or direct vote: 44,243,875

2. Shared power to vote or direct vote: 0

3. Sole power to dispose or direct the disposition: 44,243,875

4. Shared power to dispose or direct the disposition: 0

(c) Principal GP has not entered into any transactions in the Shares during the past sixty days.  The transactions in the Shares on behalf of Starboard C LP during the past sixty days are set forth in Schedule A and are incorporated herein by reference.

J. Messrs. Smith, Mitchell and Feld

(a) Each of Messrs. Smith, Mitchell and Feld, as a member of Principal GP and as a member of each of the Management Committee of Starboard Value GP and the Management Committee of Principal GP, may be deemed the beneficial owner of the (i) 26,128,823Shares owned by Starboard V&O Fund, (ii) 5,862,924 Shares owned by Starboard LLC, (iii) 3,008,940 Shares owned by Starboard C LP and (iv) 9,243,188 Shares held in the Starboard Value LP Account.

Percentage: Approximately 17.0%

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(b) 1. Sole power to vote or direct vote: 0

2. Shared power to vote or direct vote: 44,243,875

3. Sole power to dispose or direct the disposition: 0

4. Shared power to dispose or direct the disposition: 44,243,875

(c) None of Messrs. Smith, Mitchell or Feld has entered into any transactions in the Shares during the past sixty days.  The transactions in the Shares on behalf of Starboard C LP during the past sixty days are set forth in Schedule A and are incorporated herein by reference.

Item 6. Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer.

Item 6 is amended to add the following:

On May 13, 2013, Starboard and the Issuer entered into a Settlement Agreement defined and described in Item 4 above and attached as Exhibit 99.1 hereto.

On May 14, 2013, Starboard R LP and Starboard R GP entered into a joinder agreement to that certain Joint Filing Agreement dated as of November 1, 2012 by and among Starboard V&O Fund, Starboard LLC, Starboard Value LP, Starboard Value GP, Principal Co, Principal GP and Messrs. Smith, Mitchell and Feld, pursuant to which each of Starboard R LP and Starboard R GP agreed to be bound by the terms and conditions set forth therein, including, the joint filing on behalf of each of them of statements on Schedule 13D, and any amendments thereto, with respect to the securities of the Issuer.  A copy of the joinder agreement is attached hereto as Exhibit 99.2 and is incorporated herein by reference.  A copy of the Joint Filing Agreement was filed as Exhibit 99.1 to the Schedule 13D.

Item 7. Material to be Filed as Exhibits.

Item 7 is amended to add the following exhibits:

99.1 Settlement Agreement, dated as of May 13, 2013, by and among Starboard and Quantum Corporation.

99.2 Joinder Agreement dated May 14, 2013 to the Joint Filing Agreement.

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CUSIP NO. 747906204

SIGNATURES

After reasonable inquiry and to the best of his knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated:  May 15, 2013

STARBOARD VALUE AND OPPORTUNITY MASTER FUND LTD By: Starboard Value LP,        its investment manager   STARBOARD VALUE AND OPPORTUNITY S LLC By: Starboard Value LP,        its manager   STARBOARD VALUE AND OPPORTUNITY C LP By: Starboard Value R LP,        its general partner   STARBOARD VALUE R LP By: Starboard Value R GP LLC,        its general partner   STARBOARD VALUE LP By: Starboard Value GP LLC,        its general partner   STARBOARD VALUE GP LLC By: Starboard Principal Co LP,        its member   STARBOARD PRINCIPAL CO LP By: Starboard Principal Co GP LLC,        its general partner   STARBOARD PRINCIPAL CO GP LLC   STARBOARD VALUE R GP LLC

By:	/s/ Jeffrey C. Smith
	Name:	Jeffrey C. Smith
	Title:	Authorized Signatory

/s/ Jeffrey C. Smith

JEFFREY C. SMITH

Individually and as attorney-in-fact for Mark R. Mitchell and Peter A. Feld

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CUSIP NO. 747906204

SCHEDULE A

Transactions in the Shares During the Past Sixty Days

Shares of Common Stock Purchased Price Per Share($) Date of Purchase

STARBOARD VALUE AND OPPORTUNITY C LP

500,000	1.2500	04/01/2013
500,000	1.2500	04/02/2013
125,000	1.2337	04/02/2013
300,000	1.2322	04/03/2013
250,000	1.2301	04/04/2013

EX-99.1

Exhibit 99.1

AGREEMENT

This Agreement (this “Agreement”) is made and entered into as of May 13, 2013, by and among Quantum Corporation, a Delaware corporation (the “Company”), and the entities and natural persons listed on Exhibit A hereto and their respective Affiliates (collectively, “Starboard”) (each of the Company and Starboard, a “Party” to this Agreement, and collectively, the “Parties”).

RECITALS

WHEREAS, the Company and Starboard have engaged in various discussions and communications concerning the Company’s business, assets and financial performance;

WHEREAS, Starboard is deemed to beneficially own shares of common stock of the Company (the “Common Stock”) totaling, in the aggregate, 44,243,875 shares, including shares underlying the Company’s convertible senior subordinated notes, or approximately seventeen percent (17.0%)of the Common Stock of the Company issued and outstanding on the date hereof; and

WHEREAS, the Company and Starboard have determined to come to an agreement with respect to the election of members of the Company’s board of directors (the “Board”) at the 2013 annual meeting of stockholders of the Company (the “2013 Annual Meeting”) and certain other matters, as provided in this Agreement.

NOW, THEREFORE, in consideration of the foregoing premises and the mutual covenants and agreements contained herein, and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Parties hereto, intending to be legally bound hereby, agree as follows:

1.             Board Matters; Board Appointments; 2013 Annual Meeting.

(a)           The Company agrees that the Board and all applicable committees of the Board shall take all necessary actions, effective immediately following the execution of this Agreement, to (i) increase the size of the Board from eight (8) members to nine (9) members, and (ii) appoint Jeffrey Smith (“Nominee One”) as a member of the Board.  The Company further agrees that prior to the mailing of its definitive proxy statement for the 2013 Annual Meeting, the Board and all applicable committees of the Board shall take all necessary actions, subject to Section 1(d) and (j) below, to nominate Louis DiNardo (“Nominee Two”) and Philip Black (“Nominee Three,” and together with Nominee One and Nominee Two, the “Starboard Nominees”) for election to the Board at the 2013 Annual Meeting.  During the Standstill Period (as defined below), the Board and all applicable committees of the Board shall not increase the size of the Board to more than nine (9) directors.

(b)           Upon the execution of this Agreement, Starboard hereby agrees not to (i) nominate any person for election at the 2013 Annual Meeting, (ii) submit any proposal for consideration at, or bring any other business before, the 2013 Annual Meeting, directly or indirectly, or (iii) initiate, encourage or participate in any “withhold” or similar campaign with respect to the 2013 Annual Meeting, directly or indirectly, and shall not permit any of its Affiliates or Associates to do any of the items in this Section 1(b). Starboard shall not publicly or privately encourage or support any other stockholder to take any of the actions described in this Section 1(b).

(c)           The Company agrees that it will recommend, support and solicit proxies for the election of the Starboard Nominees at the 2013 Annual Meeting in the same manner as for the Company’s other nominees standing for election to the Board at the 2013 Annual Meeting.

(d)           The Company agrees that if any of the Starboard Nominees or any Replacement Director (as defined below) is unable to serve as a director, resigns as a director or is removed as a director prior to the 2014 annual meeting of stockholders of the Company (the “2014 Annual Meeting”), and at such time Starboard beneficially owns in the aggregate, excluding shares of Common Stock underlying the Company’s convertible senior subordinated notes, at least three percent (3.0%) of the Company’s then outstanding Common Stock (subject to adjustment for stock splits, reclassifications, combinations and similar adjustments), Starboard shall have the ability to recommend a substitute person(s) for approval by the Corporate Governance and Nominating Committee of the Board (the “Governance Committee”), in good faith after exercising its fiduciary duties, which approval shall not be unreasonably withheld (any such replacement nominee recommended in accordance with the terms of this Section 1(d) shall be referred to as the “Replacement Director”).  Any Replacement Director shall (i) other than in the case of a substitute for Nominee One, be independent of Starboard, (ii) qualify as “independent” pursuant to NYSE listing standards, as do Nominee Two and Nominee Three, and (iii) have relevant financial and business experience. In the event the Governance Committee does not accept a substitute person recommended by Starboard, Starboard will have the right to recommend additional substitute person(s), who meet the requirements of (i) through (iii) in the preceding sentence. Upon the recommendation of a Replacement Director nominee by the Governance Committee, the Board shall vote on the appointment of such Replacement Director to the Board no later than five (5) business days after the Governance Committee recommendation of such Replacement Director; provided, however, that if the Board does not elect such Replacement Director to the Board, the Parties shall continue to follow the procedures of this Section 1(d) until a Replacement Director is elected to the Board.

(e)           At the 2013 Annual Meeting, Starboard agrees to appear in person or by proxy at the 2013 Annual Meeting and vote all shares of Common Stock beneficially owned by it (i) in favor of the election of each of the Company’s nominees for election to the Board (ratably with respect to all nominees) and (ii) and in accordance with the Board’s recommendation with respect to the Company’s “say-on-pay” proposal, unless Institutional Shareholder Services Inc. recommends otherwise with respect to such “say-on-pay” proposal.

(f)           Starboard agrees that it will cause its Affiliates and Associates to comply with the terms of this Agreement. As used in this Agreement, the terms “Affiliate” and “Associate” shall have the respective meanings set forth in Rule 12b-2 promulgated by the Securities and Exchange Commission under the Securities Exchange Act of 1934, as amended, or the rules or regulations promulgated thereunder (the “Exchange Act”) and shall include all persons or entities that at any time during the term of this Agreement become Affiliates or Associates of any person or entity referred to in this Agreement.

(g)           As of the date of this Agreement, each of Nominee Two and Nominee Three is appointed as an observer to the Board (the “Board Observers”) until the 2013 Annual Meeting. Each of the Board Observers will (i) receive copies of all notices and written information furnished to the full Board, reasonably in advance of each meeting to the extent practicable, and (ii) be permitted to be present at all meetings of the full Board (whether by telephone or in person). Notwithstanding the foregoing, (A) the Company shall be entitled to withhold any information and exclude the Board Observers from any meeting, or any portion thereof, as is reasonably determined by the Company to be necessary to protect the Company’s attorney-client privilege, or as otherwise may be appropriate until the Board Observers are elected to the Board, and (B) the Board Observers shall execute a confidentiality agreement in form and substance reasonably acceptable to the Company with respect to the information and discussions to which the Board Observers will have access.

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(h)           The Company shall use its reasonable best efforts to hold the 2013 Annual Meeting no later than September 15, 2013.

(i)           The Company agrees that promptly following the date hereof, but in any event no later than thirty (30) days from the date hereof, the Board will take all action necessary to cause the appointment of Nominee One to the Leadership and Compensation Committee of the Board. The Company further agrees that promptly following the conclusion of the 2013 Annual Meeting, but in any event no later than thirty (30) days thereafter, the Board will take all action necessary to cause (i) the appointment of Nominee Two as chairman of the Governance Committee of the Board and (ii) the appointment of the Nominee Three to the Audit Committee of the Board.

(j)           Starboard agrees to obtain from Nominee One an irrevocable resignation letter pursuant to which Nominee One shall resign from the Board and all applicable committees thereof if at any time during the Standstill Period Starboard’s aggregate beneficial ownership of Common Stock, excluding shares of Common Stock underlying the Company’s convertible senior subordinated notes, decreases to less than three percent (3.0%) of the Company’s then outstanding Common Stock (subject to adjustment for stock splits, reclassifications and similar adjustments). Also at such time, the right of Starboard pursuant to Section 1(d) to participate in the recommendation of a Replacement Director to fill the vacancy caused by any such resignation of Nominee One shall automatically terminate.

(k)           Starboard shall cause each Starboard Nominee (and any Replacement Director) to agree in writing, during the term of any service as a director of the Company, (i) to comply with all policies, procedures, processes, codes, rules, standards and guidelines applicable to members of the Board, including, without limitation, the Company’s code of conduct, insider trading policy, its Regulation FD policy, its related party transactions policy and corporate governance guidelines and (ii) to keep confidential and not publicly disclose discussions and matters considered in meetings of the Board and Board committees, unless previously disclosed publicly by the Company.  Each Starboard Nominee (and any Replacement Director), within five (5) business days of appointment to serve as a director, shall submit to the Company a fully completed copy of the Company’s standard director & officer questionnaire and other reasonable and customary director onboarding documentation required by the Company in connection with the appointment or election of new Board members.

2.            Standstill Provisions.

(a)           Starboard agrees that, from the date of this Agreement until the earlier of (i) the date that is fifteen (15) business days prior to the deadline for the submission of stockholder nominations for the 2014 Annual Meeting pursuant to the Company’s bylaws or (ii) the date that is one hundred (100) days prior to the first anniversary of the 2013 Annual Meeting (the “Standstill Period”), neither it nor any of its Affiliates or Associates under its control or direction will, and it will cause each of such Affiliates and Associates not to, directly or indirectly, in any manner:

(i)      engage in any solicitation of proxies or consents or become a “participant” in a “solicitation” as such terms are defined in Regulation 14A under the Exchange Act of proxies or consents (including, without limitation, any solicitation of consents that improperly seeks to call a special meeting of stockholders), in each case, with respect to securities of the Company;

(ii)      form, join or in any way participate in any “group” (within the meaning of Section 13(d)(3) of the Exchange Act) with respect to the Common Stock (other than a “group” that includes all or some of the persons identified on Exhibit A, but does not include any other entities or persons not identified on Exhibit A as of the date hereof); provided, however, that nothing herein shall limit the ability of an Affiliate of Starboard to join the “group” following the execution of this Agreement, so long as any such Affiliate agrees to be bound by the terms and conditions of this Agreement;

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(iii)    deposit any Common Stock in any voting trust or subject any Common Stock to any arrangement or agreement with respect to the voting of any Common Stock, other than any such voting trust, arrangement or agreement solely among the members of Starboard and otherwise in accordance with this Agreement;

(iv)    seek or encourage any person to submit nominations in furtherance of a “contested solicitation” for the election or removal of directors with respect to the Company or seek, encourage or take any other action with respect to the election or removal of any directors;

(v)     (A) make any proposal for consideration by stockholders at any annual or special meeting of stockholders of the Company, (B) make any offer or proposal (with or without conditions) with respect to any  merger, acquisition, recapitalization, restructuring, disposition or other business combination involving the Company, or encourage, initiate or support any other third party in any such related activity or (C) make any public communication in opposition to any Company acquisition or disposition activity approved by the Board;

(vi)    seek, alone or in concert with others, representation on the Board, except as specifically contemplated in Section 1;

(vii)   seek to advise, encourage, support or influence any person with respect to the voting or disposition of any securities of the Company at any annual or special meeting of stockholders, except in accordance with Section 1; or

(viii)  make any request or submit any proposal to amend the terms of this Agreement other than through non-public communications with the Company that would not be reasonably determined to trigger public disclosure obligations for any Party.

(b)           Except as expressly provided in Section 1 or Section 2(a), each member of Starboard shall be entitled to:

(i)      vote their shares on any other proposal duly brought before the 2013 Annual Meeting, or otherwise vote as each member of Starboard determines in its sole discretion; or

(ii)     disclose, publicly or otherwise, how it intends to vote or act with respect to any securities of the Company, any stockholder proposal or other matter to be voted on by the stockholders of the Company and the reasons therefore; provided that, as applicable, all such activity is in compliance with the requirements of this Agreement.

3.             Representations and Warranties of the Company.

The Company represents and warrants to Starboard that (a) the Company has the corporate power and authority to execute this Agreement and to bind it thereto, (b) this Agreement has been duly and validly authorized, executed and delivered by the Company, constitutes a valid and binding obligation and agreement of the Company, and is enforceable against the Company in accordance with its terms, except as enforcement thereof may be limited by applicable bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance or similar laws generally affecting the rights of creditors and subject to general equity principles, and (c) the execution, delivery and performance of this Agreement by the Company does not and will not violate or conflict with (i) any law, rule, regulation, order, judgment or decree applicable to the Company, or (ii) result in any breach or violation of or constitute a default (or an event which with notice or lapse of time or both could constitute such a breach, violation or default) under or pursuant to, or result in the loss of a material benefit under, or give any right of termination, amendment, acceleration or cancellation of, any organizational document, agreement, contract, commitment, understanding, or arrangement to which the Company is a party or by which it is bound.

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4.             Representations and Warranties of Starboard.

Starboard represents and warrants to the Company that (a) the authorized signatory of Starboard set forth on the signature page hereto has the power and authority to execute this Agreement and any other documents or agreements to be entered into in connection with this Agreement and to bind it thereto, (b) this Agreement has been duly authorized, executed and delivered by Starboard, and is a valid and binding obligation of Starboard, enforceable against Starboard in accordance with its terms, except as enforcement thereof may be limited by applicable bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance or similar laws generally affecting the rights of creditors and subject to general equity principles, (c) the execution of this Agreement, the consummation of any of the transactions contemplated hereby, and the fulfillment of the terms hereof, in each case in accordance with the terms hereof, will not conflict with, or result in a breach or violation of the organizational documents of Starboard as currently in effect, (d) the execution, delivery and performance of this Agreement by Starboard does not and will not violate or conflict with (i) any law, rule, regulation, order, judgment or decree applicable to Starboard, or (ii) result in any breach or violation of or constitute a default (or an event which with notice or lapse of time or both could constitute such a breach, violation or default) under or pursuant to, or result in the loss of a material benefit under, or give any right of termination, amendment, acceleration or cancellation of, any organizational document, agreement, contract, commitment, understanding or arrangement to which such member is a party or by which it is bound, (e) as of the date of this Agreement, (i) Starboard is deemed to beneficially own in the aggregate 44,243,875 shares of Common Stock, including shares of Common Stock underlying the Company’s convertible senior subordinated notes, and (ii) Starboard does not currently have, and does not currently have any right to acquire, any interest in any other securities of the Company (or any rights, options or other securities convertible into or exercisable or exchangeable (whether or not convertible, exercisable or exchangeable immediately or only after the passage of time or the occurrence of a specified event) for such securities or any obligations measured by the price or value of any securities of the Company or any of its Affiliates, including any swaps or other derivative arrangements designed to produce economic benefits and risks that correspond to the ownership of Common Stock, whether or not any of the foregoing would give rise to beneficial ownership (as determined under Rule 13d-3 promulgated under the Exchange Act), and whether or not to be settled by delivery of Common Stock, payment of cash or by other consideration, and without regard to any short position under any such contract or arrangement), (f) each of Nominee Two and Nominee Three is independent of Starboard, and (g) Starboard has not, directly or indirectly, compensated or agreed to, and will not, compensate Nominee Two or Nominee Three for their service as a nominee or director of the Company with any cash, securities (including any rights or options convertible into or exercisable for or exchangeable into securities or any profit sharing agreement or arrangement), or other form of compensation directly or indirectly related to the Company or its securities, other than cash compensation, if any, to be used by Nominee Two and Nominee Three to purchase securities of the Company, which compensation has been previously disclosed to the Company, has been paid in full prior to the date hereof and Starboard has no remaining compensation obligation to Nominee Two or Nominee Three.

5.            Press Release.

Promptly following the execution of this Agreement, the Company and Starboard shall jointly issue a mutually agreeable press release (the “Mutual Press Release”) announcing certain terms of this Agreement, in the form attached hereto as Exhibit B. Prior to the issuance of the Mutual Press Release, neither the Company nor Starboard shall issue any press release or public announcement regarding this Agreement without the prior written consent of the other Party. Until the 2013 Annual Meeting, neither the Company nor Starboard or  any of the Starboard Nominees shall make any public announcement or statement that is inconsistent with or contrary to the statements made in the Mutual Press Release, except as required by law or the rules of any stock exchange or with the prior written consent of the other Party.

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6.             Specific Performance.

Each of Starboard, on the one hand, and the Company, on the other hand, acknowledges and agrees that irreparable injury to the other party hereto would occur in the event any of the provisions of this Agreement were not performed in accordance with their specific terms or were otherwise breached and that such injury would not be adequately compensable by the remedies available at law (including the payment of money damages). It is accordingly agreed that Starboard, on the one hand, and the Company, on the other hand (the “Moving Party”), shall each be entitled to specific enforcement of, and injunctive relief to prevent any violation of, the terms hereof, and the other party hereto will not take action, directly or indirectly, in opposition to the Moving Party seeking such relief on the grounds that any other remedy or relief is available at law or in equity. This Section 6 is not the exclusive remedy for any violation of this Agreement.

7.             Expenses.

The Company shall reimburse Starboard for its reasonable, documented out-of-pocket fees and expenses (including legal expenses) incurred in connection with the matters related to the 2013 Annual Meeting, the filing of a Schedule 13D amendment in connection with this Agreement and the negotiation and execution of this Agreement, provided that such reimbursement shall not exceed thirty thousand dollars ($30,000) in the aggregate.

8.             Severability.

If any term, provision, covenant or restriction of this Agreement is held by a court of competent jurisdiction to be invalid, void or unenforceable, the remainder of the terms, provisions, covenants and restrictions of this Agreement shall remain in full force and effect and shall in no way be affected, impaired or invalidated. It is hereby stipulated and declared to be the intention of the Parties that the Parties would have executed the remaining terms, provisions, covenants and restrictions without including any of such which may be hereafter declared invalid, void or unenforceable. In addition, the Parties agree to use their best efforts to agree upon and substitute a valid and enforceable term, provision, covenant or restriction for any of such that is held invalid, void or enforceable by a court of competent jurisdiction.

9.             Notices.

Any notices, consents, determinations, waivers or other communications required or permitted to be given under the terms of this Agreement must be in writing and will be deemed to have been delivered: (i) upon receipt, when delivered personally; (ii) upon receipt, when sent by facsimile (provided confirmation of transmission is mechanically or electronically generated and kept on file by the sending party); or (iii) one business day after deposit with a nationally recognized overnight delivery service, in each case properly addressed to the party to receive the same. The addresses and facsimile numbers for such communications shall be:

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If to the Company:
	Quantum Corporation
	1650 Technology Drive, Suite 800
	San Jose, California 95110
	Attention: Shawn Hall
	Telephone: (408) 944-4000
	Facsimile: (408) 944-6581
with a copy (which shall not constitute notice) to:
	Wilson Sonsini Goodrich & Rosati, Professional Corporation
	1301 Avenue of the Americas, 40th Floor
	New York, New York 10019
	Attention: Warren S. de Wied, Esq.
	Telephone: (212) 999-5800
	Facsimile: (212) 999-5899
If to Starboard or any member thereof:
	Starboard Value LP
	830 Third Avenue, 3rd Floor
	New York, New York 10022
	Attention: Jeffrey C. Smith
	Telephone: (212) 845-7977
	Facsimile: (212) 845-7988
with a copy (which shall not constitute notice) to:
	Olshan Frome Wolosky LLP
	Park Avenue Tower
	65 East 55th Street
	New York, New York 10022
	Attention: Steve Wolosky, Esq.
	Telephone: (212) 451-2333
	Facsimile: (212) 451-2222

10.           Applicable Law.

This Agreement shall be governed by and construed and enforced in accordance with the laws of the State of Delaware without reference to the conflict of laws principles thereof. Each of the Parties hereto irrevocably agrees that any legal action or proceeding with respect to this Agreement and the rights and obligations arising hereunder, or for recognition and enforcement of any judgment in respect of this Agreement and the rights and obligations arising hereunder brought by the other party hereto or its successors or assigns, shall be brought and determined exclusively in the Delaware Court of Chancery and any state appellate court therefrom within the State of Delaware (or, if the Delaware Court of Chancery declines to accept jurisdiction over a particular matter, any state or federal court within the State of Delaware). Each of the Parties hereto hereby irrevocably submits, with regard to any such action or proceeding for itself and in respect of its property, generally and unconditionally, to the personal jurisdiction of the aforesaid courts and agrees that it will not bring any action relating to this Agreement in any court other than the aforesaid courts. Each of the Parties hereto hereby irrevocably waives, and agrees not to assert in any action or proceeding with respect to this Agreement, (i) any claim that it is not personally subject to the jurisdiction of the above-named courts for any reason, (ii) any claim that it or its property is exempt or immune from jurisdiction of any such court or from any legal process commenced in such courts (whether through service of notice, attachment prior to judgment, attachment in aid of execution of judgment, execution of judgment or otherwise) and (iii) to the fullest extent permitted by applicable legal requirements, any claim that (A) the suit, action or proceeding in such court is brought in an inconvenient forum, (B) the venue of such suit, action or proceeding is improper or (C) this Agreement, or the subject matter hereof, may not be enforced in or by such courts.

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11.           Counterparts.

This Agreement may be executed in two or more counterparts, each of which shall be considered one and the same agreement and shall become effective when counterparts have been signed by each of the Parties and delivered to the other Party (including by means of electronic delivery or facsimile).

12.           Entire Agreement; Amendment and Waiver; Successors and Assigns; Third Party Beneficiaries.

This Agreement contains the entire understanding of the Parties hereto with respect to its subject matter. There are no restrictions, agreements, promises, representations, warranties, covenants or undertakings between the Parties other than those expressly set forth herein. No modifications of this Agreement can be made except in writing signed by an authorized representative of each the Company and Starboard, except that the signature of an authorized representative of the Company will not be required to permit an Affiliate of Starboard to agree to be listed on Exhibit A and be bound by the terms and conditions of this Agreement. No failure on the part of any party to exercise, and no delay in exercising, any right, power or remedy hereunder shall operate as a waiver thereof, nor shall any single or partial exercise of such right, power or remedy by such party preclude any other or further exercise thereof or the exercise of any other right, power or remedy. All remedies hereunder are cumulative and are not exclusive of any other remedies provided by law. The terms and conditions of this Agreement shall be binding upon, inure to the benefit of, and be enforceable by the Parties hereto and their respective successors, heirs, executors, legal representatives, and permitted assigns. No party shall assign this Agreement or any rights or obligations hereunder without, with respect to any member of Starboard, the prior written consent of the Company, and with respect to the Company, the prior written consent of Starboard. This Agreement is solely for the benefit of the Parties hereto and is not enforceable by any other persons.

13.           Mutual Non-Disparagement.

Subject to applicable law, each of the Parties covenants and agrees that, during the Standstill Period, or if earlier, until such time as the other Party or any of its agents, subsidiaries, affiliates, successors, assigns, officers, key employees or directors shall have breached this Section, neither it nor any of its respective agents, subsidiaries, affiliates, successors, assigns, officers, key employees or directors, shall in any way publicly disparage, call into disrepute, or otherwise defame or slander the other Parties or such other Parties’ subsidiaries, affiliates, successors, assigns, officers (including any current officer of a Party or a Parties’ subsidiaries who no longer serves in such capacity following the execution of this Agreement), directors (including any current director of a Party or a Parties’ subsidiaries who no longer serves in such capacity following the execution of this Agreement), employees, stockholders, agents, attorneys or representatives, or any of their products or services, in any manner that would damage the business or reputation of such other Parties, their products or services or their subsidiaries, affiliates, successors, assigns, officers (or former officers), directors (or former directors), employees, stockholders, agents, attorneys or representatives. For purposes of this Section 13, the Starboard Nominees shall not be deemed to be an agent, affiliate, officer, key employee or director of the Company or Starboard and no actions taken by any agent or other representative of a Party in any capacity other than as a representative of such Party shall be covered by this Agreement.

[The remainder of this page intentionally left blank]

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IN WITNESS WHEREOF, this Agreement has been duly executed and delivered by the duly authorized signatories of the Parties as of the date hereof.

QUANTUM CORPORATION
By:	/s/ Jon W. Gacek
Name:	Jon W. Gacek
Title:	President and Chief Executive Officer

STARBOARD:
STARBOARD VALUE AND OPPORTUNITY MASTER FUND LTD	STARBOARD VALUE LP
By: Starboard Value LP, its investment manager	By: Starboard Value GP LLC, its general partner
STARBOARD VALUE AND OPPORTUNITY S LLC	STARBOARD VALUE GP LLC
By: Starboard Value LP, its manager	By: Starboard Principal Co LP, its member
STARBOARD VALUE AND OPPORTUNITY C LP	STARBOARD PRINCIPAL CO LP
By: Starboard Value LP, its  investment manager	By: Starboard Principal Co GP LLC, its general partner
	STARBOARD PRINCIPAL CO GP LLC

By:	/s/ Jeffrey C. Smith
Name:	Jeffrey C. Smith
Title:	Authorized Signatory

[Signature Page to Agreement]

EXHIBIT A

STARBOARD

STARBOARD VALUE AND OPPORTUNITY MASTER FUND LTD

STARBOARD VALUE AND OPPORTUNITY S LLC

STARBOARD VALUE AND OPPORTUNITY C LP

STARBOARD VALUE LP

STARBOARD VALUE GP LLC

STARBOARD PRINCIPAL CO LP

STARBOARD PRINCIPAL CO GP LLC

JEFFREY C. SMITH

MARK R. MITCHELL

PETER A. FELD

EXHIBIT B

PRESS RELEASE

EX-99.2

Exhibit 99.2

JOINDER AGREEMENT

This JOINDER AGREEMENT (the “Joinder”) is dated as of May 14, 2013 by and between Starboard Value and Opportunity Master Fund Ltd, a Cayman Islands exempted company, Starboard Value and Opportunity S LLC, a Delaware limited liability company, Starboard Value and Opportunity C LP, a Delaware limited partnership, Starboard Value LP, a Delaware limited partnership, Starboard Value GP LLC, a Delaware limited liability company, Starboard Principal Co LP, a Delaware limited partnership, Starboard Principal Co GP LLC, a Delaware limited liability company, Jeffrey C. Smith, Mark R. Mitchell, and Peter A. Feld (collectively, the “Existing Members”) and Starboard Value R LP, a Delaware limited partnership, and Starboard Value R GP LLC, a Delaware limited liability company (the “New Members”).

WHEREAS, the Existing Members are parties to that certain Joint Filing Agreement dated as of November 1, 2012 (the “Agreement”) and that certain Joinder Agreement dated as of March 15, 2013, pursuant to which the Existing Members agreed to the joint filing on behalf of each of them of a Statement on Schedule 13D (including additional amendments thereto) with respect to the shares of Common Stock, $0.01 par value, of Quantum Corporation, a Delaware corporation; and

WHEREAS, the New Members desire to join the group formed by the Existing Members.

NOW, THEREFORE, in consideration of the premises and of the mutual covenants and agreements of the parties herein contained, the parties hereby agree as follows:

1.         Effective immediately, each of the New Members is joined as a party to the Agreement.

2.         Each of the New Members agrees to be bound by the terms of the Agreement, the terms of which are incorporated herein and made a part hereof.

3.         This Joinder may be executed in counterparts, each of which shall be deemed an original and all of which, taken together, shall constitute but one and the same instrument, which may be sufficiently evidenced by one counterpart.

[Signature page on next page]

IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be executed as of the day and year first above written.

STARBOARD VALUE AND OPPORTUNITY MASTER FUND LTD By: Starboard Value LP,        its investment manager   STARBOARD VALUE AND OPPORTUNITY S LLC By: Starboard Value LP,        its manager   STARBOARD VALUE AND OPPORTUNITY C LP By: Starboard Value R LP,        its general partner   STARBOARD VALUE R LP By: Starboard Value R GP LLC,        its general partner   STARBOARD VALUE LP By: Starboard Value GP LLC,        its general partner   STARBOARD VALUE GP LLC By: Starboard Principal Co LP,        its member     STARBOARD PRINCIPAL CO LP By: Starboard Principal Co GP LLC,        its general partner   STARBOARD PRINCIPAL CO GP LLC   STARBOARD VALUE R GP LLC

By:	/s/ Jeffrey C. Smith
	Name:	Jeffrey C. Smith
	Title:	Authorized Signatory

/s/ Jeffrey C. Smith

JEFFREY C. SMITH

Individually and as attorney-in-fact for Mark R. Mitchell and Peter A. Feld