A data center is a facility used for housing a large amount of electronic equipment, typically computers and communications equipment. As the name implies, a data center is usually maintained by an organization for the purpose of handling the data necessary for its operations. A bank for example may have a data center, where all its customers' account information is maintained and transactions involving this data are carried out. Practically every company mid-sized and upwards has some kind of data center, and large companies often have dozens of data centers.

As data is a crucial aspect of most organizational operations, organizations tend to be very protective of their data. A data center must therefore keep high standards for assuring the integrity and functionality of its hosted computer environment. This is depicted in its physical and logical layout.

Prior to and during the dot com crash, thousands of square feet of general-purpose data centers were built in the hope of filling them with servers for web hosting and application service providers. This demand went largely unrealised.
A colocation centre is a type of data center.

Physical Layout

A data center can occupy one room of a building, one or more floors, or up to the whole building. Most of the equipment is often in the form of 1U servers (so-called "pizza boxes") racked up in 19 inch rack cabinets, which are usually placed in single rows forming corridors between them. This allows people access to the front and rear of each cabinet. Some equipment such as mainframe computers and storage devices is often as big as the racks themselves, and are placed alongside them.

The physical environment of the data center is usually under strict control:

• Air conditioning is used to keep the room cool, generally around 17 degrees Celsius. This is crucial since electronic equipment in a confined space generates much excess heat, and tends to malfunction if cooling is not handled.

• Backup power is often available. This can include one or more uninterruptible power supplies and diesel generators located close by.

• Data centers typically have raised flooring made up of 2 foot (600mm) removable square tiles. These allow (in theory) all data and power cabling to be laid neatly and safely in cable trays below.

• Data centers often have elaborate fire prevention and fire extinguishing systems. Using water on operational electrical equipment can do just as much damage as a fire so using it is not an option - also ordinary water and electricity don't mix well. Originally halon gas was used in the event of a fire to extinguish flames - an inert gas that pushes all the oxygen out of the room. However this has now been banned in some countries because of the danger it poses to people if they are trapped in the same room without emergency breathing oxygen supplies. More recent alternatives include Argonite and FM200, and even systems based on ultra-pure water.

• Physical security also plays a large role with data centers. Personal access to the site is usually restricted to a select few. Video camera survellience and permanent security guards are almost always present if the data center is large or contains sensitive information on any of the systems within .