X0303 4 2009-07-31 false 0001373671 Isilon Systems, Inc. ISLN 0001378830 Patel Sujal M C/O ISILON SYSTEMS, INC. 3101 WESTERN AVENUE SEATTLE WA 98121 true true false false President & CEO Common Stock 2009-07-31 4 S false 12000 5.0151 D 2913164 D The sales reported were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 5, 2008. The amount and price reported in this Column 4 reflect the aggregate number and weighted-average purchase price, respectively, of the securities acquired. These shares were purchased in multiple transactions at prices ranging from $5.00 to $5.075, inclusive. For all transactions reported in this Form 4 utilizing a weighted-average price, the reporting person undertakes to provide to the issuer, any security holder of the issuer, or the SEC staff, upon request, information regarding the number of shares sold at each price within the range. Keenan Conder, Attorney-in-Fact 2009-08-04