VNET [21Vianet] 6-K/A: 21Vianet Group, Inc. Reports Unaudited Fourth Quarter and

[21Vianet Group, Inc. Reports Unaudited Fourth Quarter and Full Year 2013 Financial Results 4Q13 Net Revenues Up 30.6% YOY to RMB545.9 Million 4Q13 Adjusted EBITDA Up 31.4% YOY to RMB102.9 Million Live Conference Call to be Held at 8:00 PM U.S. Eastern Time, March 6, 2014 BEIJING, March 6, 2014 (GLOBE NEWSWIRE) — 21Vianet Group, Inc. (Nasdaq: VNET) (“21Vianet” or] [EXPLANATORY NOTE 21Vianet Group, Inc. By : Shang-Wen Hsiao Chief Financial Officer Press Release 6-K/A 1 d688339d6ka.htm AMENDMENT NO. 1 TO FORM 6-K]

VNET [21Vianet] 6-K: (Original Filing)

[21Vianet Group, Inc. Reports Unaudited Fourth Quarter and Full Year 2013 Financial Results 4Q13 Net Revenues Up 30.6% YOY to RMB545.9 Million 4Q13 Adjusted EBITDA Up 31.4% YOY to RMB102.9 Million Live Conference Call to be Held at 8:00 PM U.S. Eastern Time, March 6, 2014 BEIJING, March 6, 2014 (GLOBE NEWSWIRE) — 21Vianet Group, Inc. (Nasdaq: VNET) (“21Vianet” or] [FORM 6-K 21Vianet Group, Inc. M5, 1 Jiuxianqiao East Road, Chaoyang District Beijing 100016 The People’s Republic of China (86 10) 8456 2121 x ¨ Form 20-F ¨ ¨ 21Vianet Group, Inc. Shang-Wen Hsiao Chief Financial Officer 6-K 1 d689321d6k.htm FORM 6-K]

VNET [21Vianet] 6-K: 21Vianet Group, Inc. Reports Unaudited Fourth Quarter and

[21Vianet Group, Inc. Reports Unaudited Fourth Quarter and Full Year 2013 Financial Results 4Q13 Net Revenues Up 30.6% YOY to RMB545.9 Million 4Q13 Adjusted EBITDA Up 31.4% YOY to RMB102.9 Million Live Conference Call to be Held at 8:00 PM U.S. Eastern Time, March 6, 2014 BEIJING, March 6, 2014 (GLOBE NEWSWIRE) — 21Vianet Group, Inc. (Nasdaq: VNET) (“21Vianet” or] [FORM 6-K 21Vianet Group, Inc. M5, 1 Jiuxianqiao East Road, Chaoyang District Beijing 100016 The People’s Republic of China (86 10) 8456 2121 x ¨ Form 20-F ¨ ¨ 21Vianet Group, Inc. Shang-Wen Hsiao Chief Financial Officer 6-K 1 d689321d6k.htm FORM 6-K]

VNET [21Vianet] SC 13G/A: (Original Filing)

[SCHEDULE 13G (Rule 13d-102) (Amendment No. 1) 21Vianet Group, Inc. (Name of Issuer) Class A Ordinary Shares, par value US$0.00001 per share 90138A103 (CUSIP Number) December 31, 2013 (Date of Event Which Requires Filing of this Statement) ¨ Rule 13d-1(b) ¨ Rule 13d-1(c) ý Rule 13d-1(d) Page 2 of 7 Pages 13G ­ CUSIP No. 90138A103 1) NAME OF REPORTING]

VNET [21Vianet] SC 13G/A: SCHEDULE 13G (Rule 13d-102) (Amendment No. 1) 21Vianet

[SCHEDULE 13G (Rule 13d-102) (Amendment No. 1) 21Vianet Group, Inc. (Name of Issuer) Class A Ordinary Shares, par value US$0.00001 per share 90138A103 (CUSIP Number) December 31, 2013 (Date of Event Which Requires Filing of this Statement) ¨ Rule 13d-1(b) ¨ Rule 13d-1(c) ý Rule 13d-1(d) Page 2 of 7 Pages 13G ­ CUSIP No. 90138A103 1) NAME OF REPORTING]

VNET [21Vianet] SC 13G/A: (Original Filing)

[Item 1: Reporting Person - FMR LLC Item 4: Delaware Item 5: 28,709,448 Item 6: 0 Item 7: 35,749,182 Item 8: 0 Item 9: 35,749,182 Item 11: 12.634% Item 12: HC Cusip #90138A921 Item 1: Reporting Person - Edward C. Johnson 3d Item 5: 0 Item 6: 0 Item 7: 35,749,182 Item 8: 0 Item 9: 35,749,182 Item 11: 12.634%]

VNET [21Vianet] SC 13G/A: Item 1: Reporting Person – FMR LLC Item

[Item 1: Reporting Person - FMR LLC Item 4: Delaware Item 5: 28,709,448 Item 6: 0 Item 7: 35,749,182 Item 8: 0 Item 9: 35,749,182 Item 11: 12.634% Item 12: HC Cusip #90138A921 Item 1: Reporting Person - Edward C. Johnson 3d Item 5: 0 Item 6: 0 Item 7: 35,749,182 Item 8: 0 Item 9: 35,749,182 Item 11: 12.634%]

VNET [21Vianet] SC 13G/A: (Original Filing)

[1 Name of reporting person Sheng Chen 2 Check the appropriate box if a member of a group ¨ ¨ (a) 3 SEC use only 4 Citizenship or place of organization The People’s Republic of China Number of shares beneficially owned by each reporting person with 5 Sole voting power 1 43,819,561 ordinary shares 6 Shared voting power 0 7]

VNET [21Vianet] SC 13G/A: JOINT FILING AGREEMENT nd Waddell & Reed Financial,

[JOINT FILING AGREEMENT nd Waddell & Reed Financial, Inc. Waddell & Reed Financial Services, Inc. Waddell & Reed, Inc. Waddell & Reed Investment Management Company Ivy Investment Management Company EX-1 2 d663070dex1.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 d663070dex2.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 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 Waddell & Reed Financial Services, Inc.] [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 856,100 (See Item 4)]

VNET [21Vianet] SC 13G/A: (Original Filing)

[JOINT FILING AGREEMENT nd Waddell & Reed Financial, Inc. Waddell & Reed Financial Services, Inc. Waddell & Reed, Inc. Waddell & Reed Investment Management Company Ivy Investment Management Company EX-1 2 d663070dex1.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 d663070dex2.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 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 Waddell & Reed Financial Services, Inc.] [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 856,100 (See Item 4)]

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