X0303 4 2010-08-02 false 0001373671 Isilon Systems, Inc. ISLN 0001186035 HELSEL BRETT 3101 WESTERN AVENUE SEATTLE WA 98121 false true false false SVP Engineering Common Stock 2010-08-02 4 M false 37500 4.76 A 45700 D Common Stock 2010-08-02 4 M false 12500 2.57 A 58200 D Common Stock 2010-08-02 4 S false 25000 18.0593 D 33200 D Common Stock 2010-08-02 4 S false 12500 18.0611 D 20700 D Common Stock 2010-08-02 4 S false 12500 18.0657 D 8200 D Stock Option (Right to Buy) 4.76 2010-08-02 4 M false 37500 0 D 2018-05-12 Common Stock 37500 252500 D Stock Option (Right to Buy) 2.57 2010-08-02 4 M false 12500 0 D 2019-05-15 Common Stock 12500 82500 D The option is exercisable at the rate of 25% of the shares on March 11, 2009 and 1/12th of the remaining shares on each quarterly anniversary thereafter, such that the option will be fully exercisable on March 11, 2012. The option is exercisable at the rate of 25% of the shares on May 1, 2010 and 1/12th of the remaining shares on each quarterly anniversary thereafter, such that the option will be fully exercisable on May 1, 2013. The sales reported by Mr. Helsel were effected pursuant to a Rule 10b5-1 trading plan adopted on February 25, 2010. 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 $17.75 to $18.60, 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 in footnote (4) to this Form 4. The sales reported by Mr. Helsel were effected pursuant to a Rule 10b5-1 trading plan adopted on February 25, 2010. 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 $17.78 to $18.59, 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 in footnote (6) to this Form 4. The sales reported by Mr. Helsel were effected pursuant to a Rule 10b5-1 trading plan adopted on February 25, 2010. 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 $17.78 to $18.59, 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 in footnote (8) to this Form 4. Keenan M. Conder, Attorney-in-Fact 2010-08-04