Legacy Glossary

This is a glossary of older terms. While many of the definitions are unchanged, some of the definitions may be out of date and some of the terms may no longer be in use in the Data Center industry. This legacy glossary provides definitions for hundreds of information and communications technology (ICT) and data center terms and acronyms. Arranged alphabetically and searchable, the glossary explains common industry vocabulary.
1 A B C D E F G H I K L M N O P R S T U V W Z
Unshielded Twisted-pair Cable (UTP)

An electrically conducting cable, comprising one or more pairs, none of which is shielded. There may be an overall shield, in which case the cable is referred to as unshielded twisted-pair with overall shield (from ISO/IEC 11801: 1995)


A type of air conditioning system that discharges air upward into an overhead duct system


Uninterruptible power supply

UPS, Rotary

A flywheel-driven UPS that is used for applications requiring ride-through of short-duration power system outages, voltage dips, etc. The flywheel-driven rotary UPS typically does not include batteries, and support times are usually on the order of a few seconds to a few minutes

UPS, Static

Typically uses batteries as an emergency power source to provide power to data communications facilities until emergency generators come on line


* The time during which a computer is operational. Downtime is the time when it isn't operational
* Sometimes measured in terms of a percentile. For example, one standard for uptime that is sometimes discussed is a goal called five 9s, which is a computer that is operational 99.999 percent of the time

Utility Computing

The vision of utility computing is to access information services in a fashion similar to those provided by telephone, cable TV, or electric utilities. It is a service provisioning model in which a service provider makes computing resources and infrastructure management available to the customer as needed and charges them for specific usage rather than a flat rate. Like other types of ondemand computing, such as grid computing, the utility model seeks to maximize the efficient use of resources and/or minimize associated costs