Data Domain, Inc. Watch

from S-1/A 6 pages Second Amendment to Amended and Restated Investors’ Rights Agreement

from S-1/A 7 pages Amendment to Amended and Restated Investors’ Rights Agreement

from S-1/A 2 pages Number Ddup Datadomain Incorporated Under the Laws of the State of Delaware Shares See Reverse for Certain Definitions Cusip 23767p 10 9 This Certifies That Is the Record Holder of Fully Paid and Nonassessable Shares of Common Stock, $0.0001 Par Value, of Data Domain, Inc. Transferable on the Books of the Corporation in Person or by Duly Authorized Attorney Upon Surrender of This Certificate Properly Endorsed. This Certificate Is Not Valid Until Countersigned by the Transfer Agent and Registered by the Registrar. Witness the Facsimile Seal of the Corporation and the Facsimile Signatures of Its Duly Authorized Officers. Dated: President & Chief Executive Officer Secretary Countersigned and Registered: Wells Fargo Bank, N. A. Transfer Agent and Registrar By: Authorized Signature

from S-1 27 pages Data Domain, Inc. Amended and Restated Investors’ Rights Agreement March 14, 2007