CoreSite Realty Corporation is an owner, developer and operator of strategically located data centers in some of the growing data center markets in the United States, including Los Angeles, the San Francisco Bay and Northern Virginia areas, Chicago and New York City. Its data centers feature ample and redundant power, advanced cooling and security systems and many are points of dense network interconnection. It leases its space to a customer base ranging from enterprise customers to less space-intensive, more network-centric customers. As of December 31, 2009, its largest customer represented approximately 5.7% of its annualized rent. As of December 31, 2009, its property portfolio included 10 operating data center facilities, one data center under construction and one development site, which comprise over two million net rentable square feet, of which approximately one million NRSF is existing data center space. The Company focuses on becoming a real estate investment trust.