Data Domain to Attend VMworld 2007 as a Silver Sponsor

Market Wire, September, 2007

What:         Data Domain (NASDAQ: DDUP) today announced that it will be a
              Silver Sponsor of VMworld, hosted by VMware, on September
              11-13 at the Moscone Center in San Francisco. VMworld brings
              together thousands of IT professionals and executives,
              developers, technology providers and industry experts in the
              largest virtualization/storage industry event.

              Data Domain (booth 1036), a VMware Technology Alliance
              Partner, will showcase its market leading Deduplication
              Storage systems for a broad range of nearline applications.
              The company's systems significantly reduce backup data volume
              to lower backup costs and simplify data recovery. Data Domain
              allows for easy and efficient integration with the latest
              VMware backup processes, achieving up to 40x data reduction
              of .vmdk files and enabling remote replication via the WAN.

Session:      "Optimizing Data Protection in Virtual Environments with
              Deduplication and WAN Acceleration (panel discussion)"

              Date/Time/Location: Tuesday, September 11th, 5:00pm-6:00pm
              PT, Esplanade 303

              Data Domain Panelist: Devin Hamilton, Senior Technology
              Specialist

              Session Description: Like physical systems, virtual machines
              contain large quantities of important data that needs to be
              protected to ensure regulatory compliance, recoverability and
              disaster recovery. As organizations expand their use of
              virtualization, the amount of important data in virtual
              machines also grows, creating challenges in efficiently
              storing, accessing and transferring that data. Deduplication
              and WAN acceleration are two technologies that customers are
              using to optimize their storage and bandwidth usage,
              particularly for data protection. In this session, you'll
              hear from leading vendors about their products for
              deduplication and WAN acceleration and how they are being
              used by VMware customers to address key challenges in
              efficient data protection.


Session:      "Data Protection Best Practices--Optimizing backup/recovery
              for branch and VMware environment"

              Date/Time/Location: Tuesday, September 11th / 2:00pm-2:30pm /
              Cisco's Booth #429

              Speakers: Devin Hamilton, Senior Technology Specialist, Data
              Domain and Feng Meng, Product Marketing Manager, Cisco Wide
              Area Application Services


Session:      "Data Protection Best Practices--Optimizing backup/recovery
              for branch and VMware environment"

              Date/Time/Location: Wednesday, September 12th / 10:00am-
              10:30am / Cisco's Booth #429

              Speakers: Devin Hamilton, Senior Technology Specialist, Data
              Domain and Feng Meng, Product Marketing Manger, Cisco Wide
              Area Application Services

Event:        VMworld 2007
              September 11-13
              Moscone Center
              San Francisco, CA

Registration: For additional event information or to attend the conference,
              visit  http://www.vmware.com/vmworld/ .

Data Domain
Booth:        Booth #1036

ABOUT DATA DOMAIN

Data Domain® is the leading provider of Deduplication Storage systems for disk backup and network-based disaster recovery. Over 1,000 companies worldwide have deployed Data Domain's market-leading protection storage systems to significantly reduce backup data volume, lower their backup costs and simplify data recovery. Data Domain delivers the performance, reliability and scalability to address the data protection needs of enterprises of all sizes. Data Domain's products integrate into existing customer infrastructures and are compatible with leading enterprise backup software products. To find out more about Data Domain, visit www.datadomain.com . Data Domain is headquartered at 2300 Central Expressway, Santa Clara, CA 95050 and can be contacted by phone at 1-866-933-3873 or by e-mail at sales@datadomain.com .

Forward-Looking Statements

This press release contains forward-looking statements regarding our products' 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 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 more fully in our 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.