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                                                                    EXHIBIT 99.3

                                                                       EXHIBIT B

                                VOTING AGREEMENT

         VOTING AGREEMENT, dated as of May 7, 2000 (the "Agreement"), by and
among QLogic Corporation, a Delaware corporation ("Buyer"), and each shareholder
of Ancor Communications, Incorporated (the "Company"), whose signature is set
forth on the signature pages to this Agreement (each a "Shareholder" and,
collectively, the "Shareholders"). Capitalized terms which are used but not
defined herein shall have the meanings ascribed to them in the Merger Agreement
(as defined below).

                                   WITNESSETH:

         WHEREAS, simultaneously with the execution and delivery of this
Agreement, Buyer and the Company are entering into an Agreement and Plan of
Merger, dated as of the date hereof (the "Merger Agreement"), which provides for
a wholly owned subsidiary of Buyer to be merged with and into the Company in
accordance with the Minnesota Business Corporation Act and the terms of the
Merger Agreement, as a result of which the Company will be the surviving
corporation and will be a wholly owned subsidiary of Buyer;

         WHEREAS, the Shareholders have agreed to enter into this Agreement in
connection with the execution of the Merger Agreement.

         NOW, THEREFORE, in consideration of the premises and of the mutual
covenants and agreements set forth herein, the parties hereto, intending to be
legally bound, agree as follows:

         1. Agreement to Vote. At such time as the Company convenes a meeting of
or otherwise seeks a vote of, the Company's shareholders for the purpose of
approving the Merger, each of the Shareholders hereby agrees to vote all shares
of Company Common Stock owned by such Shareholder (whether held directly or
beneficially) approving the Merger.

         2. Limitation. Except for sales of Company Common Stock or except for
transfers of Company Common Stock to persons assuming this Agreement, each
Shareholder shall retain at all times the right to vote such Shareholder's
shares of Company Common Stock in such Shareholder's sole discretion and without
any other limitation on all matters, other than those set forth in Section 1,
that are at any time or from time to time presented for consideration by the
Company's shareholders generally.

         3. Representation and Warranty of the Shareholders. The Shareholders
severally, but not jointly, hereby represent and warrant to Buyer that the
signature page of this Agreement correctly sets forth the number of shares of
Company Common Stock owned by each Shareholder as of the date of this Agreement.
Each Shareholder has good title to all of the shares of Company Common Stock set
forth below his name on the signature page hereto free and clear of all liens,
security interests and encumbrances or any restrictions on transfer.

         4. Capacity. The parties hereby agree that the Shareholders are
executing this Agreement solely in their capacity as shareholders of the
Company. Nothing contained in this

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Agreement shall limit or otherwise affect, in any manner, the conduct or
exercise of the Shareholders' fiduciary duties as officers or directors of the
Company, where applicable.

         5. Termination. This Agreement shall terminate upon the earlier of (i)
the date of approval of the Merger by the Company's shareholders (ii) the
termination of the Merger Agreement in accordance with its terms, or (iii) upon
the mutual agreement of the parties hereto. In the event this Agreement is
terminated, this Agreement shall immediately become void, there shall be no
liability under this Agreement on the part of Buyer, its officers or directors
or the Shareholders, and all rights and obligations of the parties to this
Agreement shall cease and be of no further legal effect.

         6. Counterparts. This Agreement may be executed via facsimile in two or
more counterparts, each of which, when executed, shall be deemed to be an
original and all of which together shall constitute one and the same document.

         7. Governing Law. This Agreement shall be governed by and construed in
accordance with the laws of the State of Delaware, without giving effect to the
principles of conflicts of laws thereof.

                                    * * * * *

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

                               QLOGIC CORPORATION


                               By: /s/ Thomas R. Anderson
                                   ---------------------------------------------
                                   Thomas R. Anderson, Chief Financial Officer


                               SHAREHOLDERS


                               By: /s/ Gerald Bestler
                                   ---------------------------------------------
                                   Name:  Gerald Bestler
                                   Number of Shares Held:  23,000


                               By: /s/ Calvin G. Nelson
                                   ---------------------------------------------
                                   Name:  Calvin G. Nelson
                                   Number of Shares Held:  28,676


                               By: /s/ Steven E. Snyder
                                   ---------------------------------------------
                                   Name:  Steven E. Snyder
                                   Number of Shares Held:  22,885


                               By: /s/ Kenneth Hendrickson
                                   ---------------------------------------------
                                   Name:  Kenneth Hendrickson
                                   Number of Shares Held:  58,755

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