Monday, August 6, 2001		Bits & Bytes

Plenum cable: Cable that is run in the plenum spaces of buildings. In building construction, the plenum (pronounced PLEH-nuhm) is the space that is used for air circulation in heating and air conditioning systems, typically between the structural ceiling and the suspended ceiling or under a raised floor. The plenum space is typically used to house the communication cables for the buildings computer and telephone network(s). However, use of plenum areas for cable storage poses a serious hazard in the event of a fire as once the fire reaches the plenum space there are few barriers to contain the smoke and flames. Plenum cable is coated with a fire-retardant coating (usually Teflon) so that in case of a fire it does not give off toxic gasses and smoke as it burns.

Failover: A backup operation that automatically switches to a standby database, server or network if the primary system fails or is temporarily shut down for servicing. Fail over is an important fault tolerance function of mission-critical systems that rely on constant accessibility. Fail over automatically and transparently to the user redirects requests from the failed or down system to the backup system that mimics the operations of the primary system.