[JOINT FILING AGREEMENT nd day of February, 2007. Waddell & Reed Financial, Inc. Waddell & Reed Financial Services, Inc. Waddell & Reed, Inc. Waddell & Reed Investment Management Company Ivy Investment Management Company EX-1 2 d477786dex1.htm JOINT FILING AGREEMENT] [Waddell & Reed Investment Management Company - Tax ID No. 48-1106973 Investment Advisor registered under Section 203 of the Investment Advisors Act of 1940 Ivy Investment Management Company - Tax ID No. 03-0481447 Investment Advisor registered under Section 203 of the Investment Advisors Act of 1940 EX-2 3 d477786dex2.htm IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED THE SECURITY] [POWER OF ATTORNEY KNOW ALL MEN BY THESE PRESENTS, THAT IN WITNESS WHEREOF th day of November, 2010. Waddell & Reed Financial, Inc. Henry J. Herrmann Chief Executive Officer Attest: Wendy J. Hills Secretary POWER OF ATTORNEY KNOW ALL MEN BY THESE PRESENTS, THAT IN WITNESS WHEREOF th day of November, 2010. Waddell & Reed Financial Services, Inc. Henry J.] [CUSIP No. 90138A103 13G 1. NAME OF REPORTING PERSON Ivy Investment Management Company Tax ID No. 03-0481447 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) [ ] (b) [ ] 3. SEC USE ONLY 4. CITIZENSHIP OR PLACE OF ORGANIZATION NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH 5. SOLE VOTING POWER 6.]

[JOINT FILING AGREEMENT Dated: February 6, 2013 ATRIX ARTNERS HINA M Matrix China Management I, L.P. Matrix China I GP GP, Ltd. David Su Director ATRIX ARTNERS HINA M Matrix China Management I, L.P. Matrix China I GP GP, Ltd. David Su Director ATRIX HINA ANAGEMENT M Matrix China I GP GP, Ltd.] [CUSIP No. 90138A 10 3 1. Names of Reporting Persons Matrix Partners China I, L.P. 2. Check the Appropriate Box if a Member of a Group (See Instructions) ¨ (a) ¨ (b) 3. SEC Use Only 4. Citizenship or Place of Organization]

[SCHEDULE 13G/A (Amendment No. 1) 21Vianet Group, Inc (Name of Issuer) Class A Common Stock (Title of Class of Securities) 90138A103 (CUSIP Number) December 31, 2012 (Date of Event Which Requires Filing of this Statement) o Rule 13d-1(b) x Rule 13d-1(c) o Rule 13d-1(d) *The remainder of this cover page shall be filled out for a reporting person’s initial filing]