X0303 4 2010-04-29 false 0001373671 Isilon Systems, Inc. ISLN 0001378831 Weld Gwen E 3101 WESTERN AVENUE SEATTLE WA 98121 false true false false VP HR and Organizational Dev Common Stock 2010-04-29 4 S false 7000 13.2786 D 141516 D The sales reported by Ms. Weld were effected pursuant to a Rule 10b5-1 trading plan adopted on November 1, 2009. The "Amount" and "Price" reported in this Column 4 reflect the aggregate number and weighted-average price, respectively, of shares disposed. These shares were sold in multiple transactions at prices ranging from $13.15 to $13.39, inclusive. The reporting person undertakes to provide to the issuer, any security holder of the issuer, or the SEC staff, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth herein. Keenan Conder, Attorney-in-Fact 2010-04-30