A backup device
such as a hard disk
that is in a standby mode, meaning it is online and available should the primary device go offline
or fail. The system would detect the failure and automatically switch to the hot spare to use as a replacement. Hot spare is commonly used in RAID
arrays where additional drives are attached to the controller and left in standby mode until a failure occurs.
Compare with hot standby.
See hot swapping, also called hot plugging.