Colocation centre

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For the methods for the solution of differential equations, see Collocation method. For the corpus linguistics notion, see Collocation.

A colocation centre (also spelled co-location, or 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 connect them to a variety of telecommunications and network service providers—with a minimum of cost and complexity.


Many colocation providers sell to a wide range of customers, ranging from large enterprises to small companies.[1] Typically, the customer owns the 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.[2]

  • Cabinets – A cabinet is a locking unit that holds a server rack. In a multi-tenant data center, servers within cabinets share raised-floor space with other tenants, in addition to sharing power and cooling infrastructure.[3]
  • Cages – A cage is dedicated server space within a traditional raised-floor data center; it is surrounded by mesh walls and entered through a locking door. Cages share power and cooling infrastructure with other data center tenants.
  • Suites – A suite is a dedicated, private server space within a traditional raised-floor data center; it is fully enclosed by solid partitions and entered through a locking door. Suites may share power and cooling infrastructure with other data center tenants, or have these resources provided on a dedicated basis.
  • Modules – data center modules are purpose-engineered modules and components to offer scalable data center capacity. They typically use standardized components, which make them easily added, integrated or retrofitted into existing data centers, and cheaper and easier to build.[4] In a colocation environment, the data center module is a data center within a data center, with its own steel walls and security protocol, and its own cooling and power infrastructure. “A number of colocation companies have praised the modular approach to data centers to better match customer demand with physical build outs, and allow customers to buy a data center as a service, paying only for what they consume.”[5]

Building features[edit]

Buildings with data centres inside them are often easy to recognize due to the amount of cooling equipment located outside or on the roof.[6]

Colocation facilities have many other special characteristics:

A typical server rack, commonly seen in colocation
  • Fire protection systems, including passive and active elements, as well as implementation of fire prevention programmes in operations. Smoke detectors are usually installed to provide early warning of a developing fire by detecting particles generated by smouldering components prior to the development of flame. This allows investigation, interruption of power, and manual fire suppression using hand held fire extinguishers before the fire grows to a large size. A fire sprinkler system is often provided to control a full scale fire if it develops. Clean agent fire suppression gaseous systems are sometimes installed to suppress a fire earlier than the fire sprinkler system. Passive fire protection elements include the installation of fire walls around the space, so a fire can be restricted to a portion of the facility for a limited time in the event of the failure of the active fire protection systems, or if they are not installed.
  • 19-inch racks for data equipment and servers, 23-inch racks for telecommunications equipment.
  • Cabinets and cages for physical access control over tenants' equipment.
  • Overhead or underfloor cable rack (tray) and fibreguide, power cables usually on separate rack from data.
  • Air conditioning is used to control the temperature and humidity in the space. ASHRAE recommends a temperature range and humidity range for optimal electronic equipment conditions versus environmental issues.[7] The electrical power used by the electronic equipment is converted to heat, which is rejected to the ambient air in the data centre space. Unless the heat is removed, the ambient temperature will rise, resulting in electronic equipment malfunction. By controlling the space air temperature, the server components at the board level are kept within the manufacturer's specified temperature/humidity range. Air conditioning systems help keep equipment space humidity within acceptable parameters by cooling the return space air below the dew point. Too much humidity and water may begin to condense on internal components. In case of a dry atmosphere, ancillary humidification systems may add water vapour to the space if the humidity is too low, to avoid static electricity discharge problems which may damage components.
  • Low-impedance electrical ground.
  • Few, if any, windows.

Colocation data centres are often audited to prove that they live up to 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. 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".[8] Other data center compliance standards include HIPAA (Health Insurance Portability and Accountability Act (HIPAA) audit) and PCI DSS Standards.

Physical security[edit]

Most colocation centres have high levels of physical security, including on-site security guards. Others may simply be guarded continuously. They may also employ CCTV.

Some colocation facilities require that employees escort customers, especially if there are not individual locked cages or cabinets for each customer. In other facilities, a PIN code or proximity card access system may allow customers access into the building, and individual cages or cabinets have locks. Biometric security measures, such as fingerprint recognition, voice recognition and "weight matching", are also becoming more commonplace in modern facilities. Man-traps are also used, where a hallway leading into the data centre has a door at each end and both cannot be open simultaneously; visitors can be seen via CCTV and are manually authorized to enter.


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 48VDC (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.


Cooling within the data center can be done in multiple ways.Typically though, what "cooling" refers to is the removal of heat. Consider the heat you feel coming out of the back of your cable box, laptop or desktop computer. Now consider how much heat is produced from the thousands of servers and other IT equipment inside the data center. In order to keep this heat from damaging the sensitive IT equipment, data center operators utilize a few different technologies including the Computer Room Air Conditioner (CRAC), Computer Room Air Handler (CRAH) and chiller plant. More progressive operators have opted to use conductive cooling. Whereas traditional cooling technologies rely on chilled water systems, which consume and waste a lot of power and water, conductive cooling leverages refrigerant and consumes far less water and energy.

The operator of a colocation facility generally provides air conditioning for the computer and telecommunications equipment in the building. The cooling system generally includes some degree of redundancy.

In older facilities, the cooling system capacity often limits the amount of equipment that can operate in the building, more so than the available square footage.

Internal connections[edit]

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 hosted inside a colocation centre, where customers can connect for peering.[9]

External connections[edit]

Colocation facilities generally have multiple locations for fibre optic cables to enter the building, to provide redundancy so that communications can continue if one bundle of cables is damaged. Some also have wireless backup connections, for example via satellite.

See also[edit]


  1. ^ Pashke, Jeff. "Going Open – Software vendors in transition". 451 Research. Retrieved 6 March 2016. 
  2. ^ "Colocation: Managed or unmanaged?". 7L Networks. Retrieved 6 March 2016. 
  3. ^ "Colocation Benefits And How To Get Started". Psychz Networks. Retrieved 18 February 2015. 
  4. ^ DCD Intelligence “Assessing the Cost: Modular versus Traditional Build”, October 2013 Archived 7 October 2014 at the Wayback Machine.
  5. ^ John Rath, “DCK Guide To Modular Data Centers: The Modular Market”, “Data Center Knowledge”, October 2011
  6. ^ Examples can be seen at
  7. ^ "Thermal Guidelines for Data Processing Environments, 3rd Ed. - ASHRAE Store". 
  8. ^ "Colocation America". SSAE 16 Compliance. 
  9. ^ "Learn About Colocation Benefits And How To Get Started". Psychz.Net. 

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