PRESS RELEASE

Data Domain Repeats as Top In-Use and In-Plan Deduplication Vendor in Fortune 1000

TheInfoPro™ Storage Wave 11 Study Reveals that Storage Professionals See Data Domain as a Most Exciting Vendor
www.datadomain.com

SANTA CLARA, Calif. — October 22, 2008 — Data Domain, Inc. (Nasdaq: DDUP), the leading provider of deduplication storage systems, today announced that results from the TheInfoPro’s new Wave 11 Storage Study cites Data Domain as the top in-use deduplication vendor by respondents in both Fortune 1000 companies and among midsize enterprises. Further, Fortune 1000 users interviewed see Data Domain as one of the storage technology providers with the most exciting storage products and services in 2008 and moving into 2009. Additionally, according to the study’s Technology Heat Index – which gauges the immediacy of user need and planned spending – Data Domain continues to be the fastest growing in-plan deduplication technology provider by the study participants.

“TheInfoPro sees Data Domain’s achievements gain in both use and planned use with each successive Wave study. Our Wave 11 study shows that more than two-thirds of respondents plan to increase spending on deduplication technology in 2009,” said Robert Stevenson, Managing Director of Storage Research for TheInfoPro. "Quite simply, the results of our Wave 11 interviews with storage professionals show that the Fortune 1000 and midsize enterprise consider deduplication to be the most immediately needed storage solution, and that Data Domain is the top player in the category."

TheInfoPro is an independent research network and leading supplier of market intelligence for the Information Technology (IT) industry. TheInfoPro’s Storage Study details technology adoption trends and timeframes, management techniques and vendor performance data for the storage industry.

Additional results from the participants in TheInfoPro’s new Wave 11 Storage Study include:

• Data Domain is among the top five in consideration vendors for the Fortune 1000, according to the Storage Networking Technology Short List;
• Data Domain demonstrated positive movement in terms of in-plan buying among both Fortune 1000 and mid-sized companies;
• None of the Data Domain customers interviewed have indicated that they are planning to switch from Data Domain;
• Data Domain received the highest possible placement in the “Strategic Vision,” “Technical Innovation,” “Ease of Doing Business,” “Features and Functions,” “Delivery of Products as Promised,” and “Interoperability” Customer Rankings.

“TheInfoPro Wave 11 study shows very clearly that Data Domain is continuing to grow in both deployment and in brand recognition in the Fortune 1000,” said Beth White, Vice President of Marketing for Data Domain. “TheInfoPro’s detailed storage studies are an important validation of our ability to make good on technology promises, and we are pleased to be recognized by the majority of respondents as delivering high-value and exciting storage solutions.”

For more information about Data Domain deduplication storage systems, please visit www.datadomain.com.

ABOUT THEINFOPRO
TheInfoPro (TIP) is an independent research network for the Information Technology (IT) industry. Through a peer network of over 1600 of the world’s largest buyers and users of IT, including Citigroup, FedEx, McGraw-Hill, MasterCard, Pfizer, Vodafone, PepsiCo, JPMorgan Chase, and Harvard University, TIP delivers detailed budget, vendor performance and technology roadmap data without spin or bias. Known as the “voice of the customer,” TIP helps IT professionals, technology providers, and institutional investors make sound decisions on technologies, vendor relationships and investments. Founded in 2002 by alumni of Gartner, Giga, EMC, and Bell Labs, TIP is headquartered in New York City, with offices in San Francisco, Chicago, and Boston. To learn more, visit www.theinfopro.net or call 1-212-672-0010.

About Data Domain
Data Domain® is the leading provider of deduplication storage systems. Over 2100 companies worldwide have purchased Data Domain systems to reduce storage costs and simplify data management. Data Domain delivers the performance, reliability and scalability to address the data protection and nearline storage needs of enterprises of all sizes. Data Domain products integrate into existing customer infrastructures and are compatible with leading enterprise backup and archive software products. To find out more about Data Domain, visit www.datadomain.com. Data Domain is headquartered at 2421 Mission College Blvd., Santa Clara, CA 95054 and can be contacted by phone at 1-866-933-3873 or by e-mail at sales@datadomain.com.

Data Domain Forward-Looking Statements
This press release contains forward-looking statements regarding our fast growing in-plan deduplication technology provider status, top five in consideration status among responding Fortune 1000 enterprises, the immediacy of user need and planned spending on our products and services, anticipated spending on our products and services, and our ability to reduce the amount of stored back-up data and associated storage costs and to provide faster access to data and advanced levels of data protection, and other statements identified by forward-looking words such as "anticipated," "believed," "could," "estimate," "expect," "intend," "may," "should," "will" and "would" or similar words. These forward-looking statements involve risks and uncertainties, as well as assumptions that, if they do not fully materialize or prove incorrect, could cause our results to differ materially from those expressed or implied by such forward-looking statements. The risks and uncertainties include any weakening of general economic and market conditions and customer budgets for information technology spending, our ability to react to trends and challenges in our business and the markets in which we operate; our ability to anticipate market needs or develop new or enhanced products to meet those needs; market acceptance of our products; our ability to scale our distribution channels; our ability to recruit and retain personnel; our ability to compete in our industry; our ability to maintain and expand relationships with technology partners; our ability to protect our intellectual property; shortages or price fluctuations in our supply chain and the performance of our contract manufacturer; general political, economic and market conditions and events; and other risks and uncertainties described in the "Risk Factors" section of our Quarterly Report on Form 10-Q for the quarter ended June 30, 2008 and our other documents filed with or furnished to the Securities and Exchange Commission. All forward-looking statements in this press release are based on information available to us as of the date hereof, and we assume no obligation to update these forward-looking statements.

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

Contact Information

Data Domain

Edward Luboja
203-210-7404
press@datadomain.com

Lois Paul & Partners

Christen Rice
781-782-5869
pchristen_rice@lpp.com

TheInfoPro, Inc

Bernadette Abel
646-649-8539
bernadette@theinfopro.net

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