X0303 4 2010-12-17 1 0001373671 Isilon Systems, Inc. ISLN 0001112239 SEQUOIA CAPITAL X C/O SEQUOIA CAPITAL 3000 SAND HILL RD, BLDG 4-250 MENLO PARK CA 94025 0 0 1 0 0001206787 SC X MANAGEMENT LLC C/O SEQUOIA CAPITAL 3000 SAND HILL RD, BLDG 4-250 MENLO PARK CA 94025 0 0 1 0 0001127112 SEQUOIA CAPITAL X PRINCIPALS FUND LLC C/O SEQUOIA CAPITAL 3000 SAND HILL RD, BLDG 4-250 MENLO PARK CA 94025 0 0 1 0 0001119873 SEQUOIA TECHNOLOGY PARTNERS X LP C/O SEQUOIA CAPITAL 3000 SAND HILL RD, BLDG 4-250 MENLO PARK CA 94025 0 0 1 0 Common Stock 2010-12-17 2010-12-17 4 U 0 11651603 33.85 D 0 I See footnote Represents 9,291,352 shares held by Sequoia Capital X, 999,345 shares held by Sequoia Capital X Principals Fund and 1,360,906 shares held by Sequoia Technology Partners X. SC X Management, LLC is the sole general partner of Sequoia Capital X and Sequoia Technology Partners X LP, and the managing member of Sequoia Capital X Principals Fund. As a result, SC X Management LLC may be deemed to share voting and dispositive power with respect to the shares of Common Stock held by Sequoia Capital X, Sequoia Technology Partners X LP and Sequoia Capital X Principals Fund. SC X Management LLC disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein. By Sequoia Capital X, By SC X Management, LLC, its General Partner By Douglas M Leone, its Managing Member, By Melinda Dunn as attorney-in-fact 2010-12-21 By Sequoia Capital X Principals Fund LLC, By SC X Management, LLC, its General Partner By Douglas M Leone, its Managing Member, By Melinda Dunn as attorney-in-fact 2010-12-21 By Sequoia Technology Partners X LP, By SC X Management, LLC, its General Partner By Douglas M Leone, its Managing Member, By Melinda Dunn as attorney-in-fact 2010-12-21 By SC X Management, LLC, By Douglas M Leone, its Managing Member, By Melinda Dunn as attorney-in-fact 2010-12-21