Initial Statement of Beneficial Ownership (3)

FORM 3	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES	OMB APPROVAL OMB Number: 3235-0104 Estimated average burden hours per response... 0.5
	Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

1. Name and Address of Reporting Person ^*

CG Subsidiary Holdings L.L.C.

2. Date of Event Requiring Statement (MM/DD/YYYY) 1/1/2020

3. Issuer Name and Ticker or Trading Symbol

CoreSite Realty Corp [COR]

(Last) (First) (Middle)

C/O THE CARLYLE GROUP, 1001, PENNSYLVANIA AVE., N.W., SUITE 220 SOUTH

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

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

(Street)

WASHINGTON, DC 20004-2505

(City) (State) (Zip)

5. If Amendment, Date Original Filed(MM/DD/YYYY)

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 Beneficially Owned
1.Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

*Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)*
1. Title of Derivate Security (Instr. 4)	2. Date Exercisable and Expiration Date (MM/DD/YYYY)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
1. Title of Derivate Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security		6. Nature of Indirect Beneficial Ownership (Instr. 5)
Operating Partnership Units	⁽¹⁾	⁽¹⁾	Common Stock	10725390	⁽¹⁾	I	See footnotes ⁽²⁾⁽³⁾⁽⁴⁾⁽⁵⁾

Explanation of Responses:
(1)	The operating partnership units are redeemable at any time for cash or, at the election of the Issuer, exchangeable for shares of common stock on a one-for-one basis, and have no expiration date.
(2)	Consists of (i) 2,082,097 common units held by CoreSite CRP III Holdings, LLC; (ii) 421,780 common units held by CoreSite CRP III Holdings (VCOC), LLC; (iii) 1,459,136 common units held by CoreSite CRP IV Holdings, LLC; (iv) 248,488 common units held by CoreSite CRP IV Holdings (VCOC I), LLC; (v) 638,671 common units held by CoreSite CRP IV Holdings (VCOC II), LLC; and (vi) 5,875,218 common units held by CoreSite CRP V Holdings, LLC.
(3)	Following an internal reorganization and by reason of the relationships described below, the reporting person may be deemed to share beneficial ownership of the securities reported herein. The reporting person disclaims beneficial ownership of any such securities, except to the extent of its pecuniary interest therein.
(4)	Carlyle Group Management L.L.C. holds an irrevocable proxy to vote a majority of the shares of The Carlyle Group Inc., which is a publicly traded entity listed on NASDAQ. The Carlyle Group Inc. is the sole shareholder of Carlyle Holdings I GP Inc., which is the managing member of Carlyle Holdings I GP Sub L.L.C., which is the general partner of Carlyle Holdings I L.P., which, with respect to the securities reported herein, is the managing member of CG Subsidiary Holdings L.L.C., which is the sole member of TC Group, L.L.C., which is the general partner of TC Group Sub L.P., which is the managing member of each of Carlyle Realty III GP, L.L.C., CRP III AIV GP, L.L.C., Carlyle Realty IV GP, L.L.C., CRP IV AIV GP, L.L.C. and Carlyle Realty V GP, L.L.C.
(5)	Carlyle Realty III GP, L.L.C. is the general partner of Carlyle Realty III, L.P. which is the manager of CoreSite CRP III Holdings, LLC. CRP III AIV GP, L.L.C. is the general partner of CRP III AIV GP, L.P., which is the general partner of CRQP III AIV, L.P., which is the managing member of CoreSite CRP III Holdings (VCOC), LLC. Carlyle Realty IV GP, L.L.C. is the general partner of Carlyle Realty IV, L.P., which is the manager of CoreSite CRP IV Holdings, LLC. CRP IV AIV GP, L.L.C. is the general partner of CRP IV AIV GP, L.P., which is the general partner of each of CRP IV-A AIV, L.P. and CRQP IV AIV, L.P., which are the managing members of CoreSite CRP IV Holdings (VCOC I), LLC and CoreSite CRP IV Holdings (VCOC II), LLC, respectively. Carlyle Realty V GP, L.L.C. is the general partner of Carlyle Realty V, L.P., which is the manager of CoreSite CRP V Holdings, LLC.

Remarks:
Exhibit 24 -Power of Attorney

Reporting Owners
Reporting Owner Name / Address	Relationships
Reporting Owner Name / Address	Director	10% Owner	Officer	Other
CG Subsidiary Holdings L.L.C. C/O THE CARLYLE GROUP, 1001 PENNSYLVANIA AVE., N.W., SUITE 220 SOUTH WASHINGTON, DC 20004-2505		X

Signatures
CG Subsidiary Holdings L.L.C., By: Carlyle Holdings I L.P., its managing member, By: /s/ Anne Frederick, attorney-in-fact for Curtis L. Buser, Chief Financial Officer		1/13/2020
^**Signature of Reporting Person		Date