SEC FORM 4

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person^*

McIlwain Matthew S

(Last)

(First)

(Middle)

C/O MADRONA VENTURE GROUP, LLC

1000 SECOND AVE., STE. 3700

(Street)

SEATTLE

98104

(City)

(State)

(Zip)

2. Issuer Name and Ticker or Trading Symbol
Isilon Systems, Inc. [ ISLN ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
02/26/2009

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock								31,750⁽¹⁾	D
Common Stock	02/26/2009		P		50,994⁽²⁾	A	$2.252	8,665,135	I	See footnote⁽³⁾
Common Stock	02/27/2009		P		49,041⁽⁴⁾	A	$2.3043	8,714,176	I	See footnote⁽⁵⁾

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)

Explanation of Responses:

1. 4,000 shares were acquired through reporting person's 401k plan.

2. Reflects a weighted-average price. These shares were purchased in multiple transactions at prices ranging from $2.07 to $2.50, inclusive. For all transactions reported in this Form 4 utilizing a weighted-average price, the reporting person will 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.

3. Represents 6,986,632 shares held by Madrona Venture Fund I-A, LP, 760,411 shares held by Madrona Venture Fund I-B, LP and 918,092 shares held by Madrona Managing Director Fund, LLC. Mr. McIlwain is a managing director and member of various entities affiliated with Madrona Venture Group, LLC. Mr. McIlwain does not have sole voting or dispositive authority over these shares and disclaims beneficial ownership of these shares except to the extent of his pecuniary interest therein.

4. Reflects a weighted-average price. These shares were purchased in multiple transactions at prices ranging from $2.16 to $2.3518, inclusive. For all transactions reported in this Form 4 utilizing a weighted-average price, the reporting person will 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.

5. Represents 7,026,173 shares held by Madrona Venture Fund I-A, LP, 764,715 shares held by Madrona Venture Fund I-B, LP and 923,288 shares held by Madrona Managing Director Fund, LLC. Mr. McIlwain is a managing director and member of various entities affiliated with Madrona Venture Group, LLC. Mr. McIlwain does not have sole voting or dispositive authority over these shares and disclaims beneficial ownership of these shares except to the extent of his pecuniary interest therein.

	Keenan Conder, Attorney-in-Fact	03/02/2009
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
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