KKR & Global Infrastructure Partners have closed on their acquisition of CyrusOne, taking the company private.

The two firms last year announced they were acquiring the Nasdaq-listed colocation firm for $15 billion – the largest M&A deal in data center industry history.

“CyrusOne has built one of the strongest data center companies in the world and has a strong track record of development and operational expertise in addition to delivering best-in-class service to its customers,” said Waldemar Szlezak, Partner at KKR, and Will Brilliant, partner at GIP. “We are excited to work together with the company’s proven team to build on CyrusOne’s market leadership and support their customers’ growing data center infrastructure requirements. We see numerous opportunities ahead to continue expanding CyrusOne’s footprint across key global digital gateway markets and look forward to leveraging our global resources, access to long term capital and deep expertise to support the company’s growth.”

KKR’s investment is being made primarily from its global infrastructure and real estate equity strategies, and GIP’s investment is being made from its global infrastructure funds.

CyrusOne was formed in 2000, and was acquired by ABRY Partners in 2007. ABRY then sold the company to Cincinnati Bell Inc. in 2010. CyrusOne went public in 2013.

“This transaction is a testament to the tremendous work by the entire CyrusOne team,” said Dave Ferdman, co-founder and interim president and CEO of CyrusOne. “We have built one of the world’s leading data center companies with a presence across key US and international markets supporting our customers’ mission-critical digital infrastructure requirements while creating significant value for our stockholders.”

Morgan Stanley & Co. LLC and DH Capital, LLC acted as financial advisors to CyrusOne; Cravath, Swaine & Moore LLP, Venable LLP, and Eversheds Sutherland (International) LLP acted as its legal counsel.

Goldman Sachs & Co., Barclays, Wells Fargo Securities, LLC, Citigroup, and J.P. Morgan acted as financial advisors to KKR and GIP, with KKR Capital Markets leading the structuring on the financing. Kirkland & Ellis LLP and Dentons (UK & Europe) acted as legal counsel to the acquiring consortium and KKR, and Paul, Weiss, Rifkind, Wharton & Garrison LLP acted as legal counsel to GIP.

Pantheon Infrastructure, a recently-listed venture fund from Pantheon Ventures invested in the take-private of CyrusOne through a KKR-affiliated investment vehicle. The firm’s portion of the net asset value of the vehicle is approximately £21 million.

This month has also seen CyrusOne take part in a blood donation drive.

The company has teamed with Loudoun County Economic Development and the American Red Cross of Loudoun and Prince William Counties in Virginia for a blood drive campaign called #DataCentersSleeveUp.

CyrusOne said it had over 10 percent of its US employees sign up for blood donations and over 420 people from 11 industry partners participated. Other firms involved in the campaign include AWS, Microsoft, Digital Realty, Equinix, Yondr, Sabey, QTS, Stack, Aligned, Vantage, and CloudHQ.