“Perhaps most important of all, we know that our data is replicated to our contingency site within minutes, minimizing the risk of any disruption in IT functionality at our headquarters in London.” — Colin Everett
Head of IT Strategy and Architecture, Lloyds TSB Corporate Markets

Press Release

Data Domain, Inc. Reports Restatement of Previously Issued Financial Statements For The Calculation of Net Income (Loss) Per Share

SANTA CLARA, Calif. — October 29, 2007 — Data Domain, Inc. (Nasdaq: DDUP) today announced that in its previously issued financial statements for its fiscal years ended December 31, 2004, 2005 and 2006 and for its fiscal quarters ended March 31, 2006 and 2007 and June 30, 2006 and 2007, it erroneously calculated the weighted average number of shares outstanding for the purpose of determining its net income (loss) per share for each of these periods. The effect of the erroneous calculation was to understate the net loss per share for each of these periods, but in all other respects the Company's financial results and financial condition were not affected by the restatement.

Data Domain intends to file its restated Audited Consolidated Financial Statements for the years ended December 31, 2004, 2005 and 2006 as Exhibit 99.1 to a Current Report on Form 8-K that it intends to file tomorrow, which financial statements may be relied upon by investors.

The previously issued financial statements erroneously included as part of the weighted average number of shares outstanding unvested shares of common stock that were issued pursuant to the early exercise of stock options that were subject to repurchase by the Company at the end of each period. Accordingly, the Company’s previously issued financial statements covering such periods should no longer be relied upon because of this error. The effect of this error on each of these periods is as follows:





Data Domain’s independent registered public accounting firm, Ernst & Young LLP, concurs with Data Domain’s conclusion to restate the affected prior periods.

Data Domain and the Data Domain logo are trademarks or registered trademarks of Data Domain, Inc. All other trademarks used or mentioned herein belong to their respective owners.

A copy of this press release can be found on the Investor Relations page of Data Domain’s website at www.datadomain.com

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Contact Information

Data Domain

Michael P. Scarpelli
Chief Financial Officer
408.980.4800
ir@datadomain.com