The full text of the letter that EMC sent to Data Domain’s President and Chief Executive Officer follows below:

June 1, 2009

Mr. Frank Slootman
President and Chief Executive Officer
Data Domain, Inc.
2421 Mission College Boulevard
Santa Clara, California  95054

Dear Frank:

On behalf of EMC, I am pleased to submit to you and your Board of Directors a proposal to acquire Data Domain which is substantially superior to the NetApp proposal.  We are highly impressed with your business and your team, and we are confident that a business combination will deliver substantial benefits to your company’s stockholders, customers, employees and partners.  We are disappointed that we were not given an opportunity to explore a business combination prior to the announcement of your proposed transaction with NetApp, particularly since I believe you should have been aware of our interest.

EMC proposes to acquire all outstanding Data Domain common stock for $30.00 per share in cash.  This price represents a 20% premium to NetApp's cash and stock offer and is a Superior Proposal as defined in your merger agreement with NetApp.  The Board of EMC has unanimously approved this proposal. 

EMC’s proposal is not subject to any financing or due diligence contingency, and we will use existing cash balances to finance the transaction.

In order to consummate this transaction quickly, we intend to effect a first step tender offer for all outstanding Data Domain common stock followed by a second step merger for any remaining shares.  We are enclosing with this letter a form of agreement to effect our proposed transaction which is substantially identical to the agreement between you and NetApp except as to our superior price and except for changes reflecting our faster two-step structure.  We are prepared to execute this agreement immediately upon your Board of Directors’ determination that EMC has made a Superior Proposal as provided in the merger agreement with NetApp.  We are utilising the two-step structure to enable us to pay Data Domain’s stockholders as quickly as possible after signing a definitive agreement, and to further expedite this timing, we are promptly commencing the tender offer.  Consistent with the terms of your agreement with NetApp, we expect to follow the process set forth in the Annex to this letter to enter into a signed agreement with Data Domain as quickly as possible.

In comparison to your proposed transaction with NetApp, EMC’s proposal represents a far superior alternative for your stockholders.

- EMC’s proposal provides higher absolute value for each Data Domain share.
  - As an all cash offer, EMC’s proposal offers greater certainty of value.
  - With a tender offer structure, EMC’s transaction offers a faster time to close.

A transaction with EMC also represents a far more compelling alternative to your customers, employees and partners.  For example:

ˇ The customer use cases for Data Domain’s data deduplication technologies and EMC’s existing data deduplication technologies are generally distinct.  The combination of Data Domain’s leading target-based deduplication technologies and EMC’s leading source-based deduplication technologies will allow the combined company to address the broad range of customers’ data protection needs in a unified and complementary way.  The marketplace for storage software solutions is complex, dynamic and highly competitive.  Having superior deduplication technology solutions that combine the strengths of Data Domain and EMC in this storage software marketplace will help customers better achieve their needs as the market continues to evolve.
ˇ EMC’s world-class sales organisation of approximately 9,000 professionals in over 400 offices around the globe, its extensive network of several thousand partners and its strong relationships with many of the premier enterprises worldwide will dramatically accelerate the deployment of Data Domain’s solutions.
ˇ The combination of Data Domain’s and EMC’s technologies will provide the basis for the next-generation of disk-based back-up and archiving solutions for customers by providing functionally superior and cost-effective alternatives to tape-based information backup.
ˇ Next-generation disk-based back-up and archiving solutions represent key enabling technologies for the build-out and customer use of true high-reliability cloud computing infrastructures for both enterprises’ own virtualised data centres (“private” clouds) and third party providers (“public” clouds).

We will maintain the senior management team under your leadership and operate Data Domain as a product division within EMC.  As a part of EMC, Data Domain will have access to EMC’s superior global resources and we will enhance this division with additional EMC technology, products and capital.  The combination with EMC represents a unique opportunity for your management team and employees to benefit from the greater resources of EMC and to become important leaders within a larger organisation committed to leadership in next-generation information infrastructure solutions.

EMC has a long and distinguished track record of skillfully acquiring and integrating leading technology companies.  Because of our considerable experience, I am confident that we can successfully integrate our companies, retain the talented employees of Data Domain and realise the full potential of this combination.

We look forward to executing the definitive agreement attached.

                                                                        Very truly yours,

                                                                        /s/ Joseph M. Tucci

                                                                        Joseph M. Tucci                                                                         Chairman, President and Chief Executive Officer                                                                         EMC Corporation