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A colocation center (also spelled co-location, or shortened to colo) or "carrier hotel", is a type of data centre where equipment, space, and bandwidth are available for rental to retail customers. Colocation facilities provide space, power, cooling, and physical security for the server, storage, and networking equipment of other firms and also connect them to a variety of telecommunications and network service providers with a minimum of cost and complexity[clarification needed].
Many colocation providers sell to a wide range of customers, ranging from large enterprises to small companies. Typically, the customer owns the information technology (IT) equipment and the facility provides power and cooling. Customers retain control over the design and usage of their equipment, but daily management of the data center and facility are overseen by the multi-tenant colocation provider.
Buildings with data centres inside them are often easy to recognize by the amount of cooling equipment located outside or on the roof.
Colocation facilities have many other special characteristics:
Colocation data centres are often audited to prove that they attain certain standards and levels of reliability; the most commonly seen systems are SSAE 16 SOC 1 Type I and Type II (formerly SAS 70 Type I and Type II) and the tier system by the Uptime Institute or TIA. For service organizations today, SSAE 16 calls for a description of its "system". This is far more detailed and comprehensive than SAS 70's description of "controls". Other data center compliance standards include Health Insurance Portability and Accountability Act (HIPAA) audit and PCI DSS Standards.
Colocation facilities generally have generators that start automatically when utility power fails, usually running on diesel fuel. These generators may have varying levels of redundancy, depending on how the facility is built. Generators do not start instantaneously, so colocation facilities usually have battery backup systems. In many facilities, the operator of the facility provides large inverters to provide AC power from the batteries. In other cases, customers may install smaller UPSes in their racks.
Some customers choose to use equipment that is powered directly by 48 VDC (nominal) battery banks. This may provide better energy efficiency, and may reduce the number of parts that can fail, though the reduced voltage greatly increases necessary current, and thus the size (and cost) of power delivery wiring. An alternative to batteries is a motor–generator connected to a flywheel and diesel engine.
Many colocation facilities can provide redundant, A and B power feeds to customer equipment, and high end servers and telecommunications equipment often can have two power supplies installed.
Colocation facilities are sometimes connected to multiple sections of the utility power grid for additional reliability.
Colocation facility owners have differing rules regarding cross-connects between their customers, some of whom may be carriers. These rules may allow customers to run such connections at no charge, or allow customers to order such connections for a monthly fee. They may allow customers to order cross-connects to carriers, but not to other customers. Some colocation centres feature a "meet-me-room" where the different carriers housed in the centre can efficiently exchange data.
Most peering points sit in colocation centres and because of the high concentration of servers inside larger colocation centres, most carriers will be interested in bringing direct connections to such buildings. In many cases, there will be a larger Internet exchange point hosted inside a colocation centre, where customers can connect for peering.