Exhibit 32.2

CERTIFICATION OF CHIEF FINANCIAL OFFICER

PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

I, William Richter, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that the Quarterly Report on Form 10-Q of Isilon Systems, Inc. for the three and six months ended June 30, 2009 fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 and that information contained in such Quarterly Report on Form 10-Q fairly presents, in all material respects, the financial condition and results of operations of Isilon Systems, Inc.

Dated: July 31, 2009	By:	/s/ WILLIAM RICHTER
	Name:	William Richter
	Title:	Interim Chief Financial Officer and Vice President of Finance
		(Principal Accounting and Financial Officer)