Exhibit 3

IRREVOCABLE PROXY

The undersigned shareholder (the “Shareholder”) of Advanced Digital Information Corporation, a Washington corporation (the “Company”), hereby irrevocably (to the fullest extent permitted by law) appoints Quantum Corporation, a Delaware corporation (“Parent”), acting through any of its Chief Executive Officer, Chief Financial Officer or General Counsel, as the sole and exclusive attorneys and proxies of the undersigned, with full power of substitution and resubstitution, to vote and exercise all voting and related rights (to the full extent that the undersigned is entitled to do so) with respect to all of the shares of capital stock of the Company that now are or hereafter may be beneficially owned by the undersigned, and any and all other shares or equity securities of the Company issued or issuable in respect thereof on or after the date hereof (collectively, the “Shares”) in accordance with the terms of this Irrevocable Proxy until the Expiration Date (as defined below); provided, however, that such proxy and voting and related rights are expressly limited to the matters discussed in clauses (i) through (iii) in the fourth paragraph of this Irrevocable Proxy. Upon the undersigned’s execution of this Irrevocable Proxy, any and all prior proxies given by the undersigned with respect to any Shares are hereby revoked and the undersigned agrees not to grant any subsequent proxies with respect to the Shares until after the Expiration Date.

This Irrevocable Proxy is irrevocable to the fullest extent permitted by law, is coupled with an interest and is granted pursuant to that certain Voting Agreement of even date herewith by and between Parent and the undersigned shareholder (the “Voting Agreement”), and is granted in consideration of Parent entering into that certain Agreement and Plan of Merger of even date herewith (the “Merger Agreement”), among Parent, Agate Acquisition Corp., a Washington corporation and wholly-owned subsidiary of Parent (“Merger Sub”), and the Company. The Merger Agreement provides for, among other things the merger of Merger Sub with and into the Company, pursuant to which all outstanding shares of capital stock of the Company will be converted into the right to receive the consideration set forth in the Merger Agreement.

As used herein, the term “Expiration Date” shall mean the earlier to occur of (i) such date and time as the Merger Agreement shall have been terminated pursuant to Article VIII thereof, (ii) such date and time as the Merger shall become effective in accordance with the terms and provisions of the Merger Agreement, or (iii) May 2, 2007.

The attorneys and proxies named above, and each of them, are hereby authorized and empowered by the undersigned, at any time prior to the Expiration Date, to act as the undersigned’s attorney and proxy to vote the Shares, and to exercise all voting, consent and similar rights of the undersigned with respect to the Shares (including, without limitation, the power to execute and deliver written consents) at every annual, special, adjourned or postponed meeting of shareholders of the Company and in every written consent in lieu of such meeting:

(i) in favor of the adoption of the Merger Agreement, and in favor of each of the other actions contemplated by the Merger Agreement and any action required in furtherance thereof;

(ii) against approval of any proposal made in opposition to, or in competition with, consummation of the Merger or any other transactions contemplated by the Merger Agreement; and

(iii) against any of the following actions (other than those actions that relate to the Merger and any other transactions contemplated by the Merger Agreement): (A) any merger, consolidation, business combination, sale of assets, reorganization or recapitalization of the Company or any subsidiary of the Company with any party, (B) any sale, lease or transfer of any significant part of the assets of the Company or any subsidiary of the Company, (C) any reorganization, recapitalization, dissolution, liquidation or winding up of the Company or any subsidiary of the Company, (D) any material change in the capitalization of the Company or any subsidiary of the Company, or the corporate structure of the Company or any subsidiary of the Company, or (E) any other action that is intended, or could reasonably be expected to, impede, interfere with, delay, postpone, discourage or adversely affect the Merger or any other transactions contemplated by the Merger Agreement.

The attorneys and proxies named above may not exercise this Irrevocable Proxy on any other matter. The undersigned shareholder may vote the Shares on all other matters.

Any obligation of the undersigned hereunder shall be binding upon the successors and assigns of the undersigned.

This Irrevocable Proxy shall terminate, and be of no further force and effect, automatically upon the Expiration Date.

Dated: May 2, 2006	JOHN W. STANTON
	By:	/s/ John W. Stanton
	Name:	John W. Stanton
	Title:	N/A
	SPOUSE
	By:	/s/ Theresa E. Gillespie
	Name:	Theresa E. Gillespie
	Title:	N/A

***** IRREVOCABLE PROXY ****