Definition - What does Hot Spare mean?
A hot spare is a backup device that is usually in standby mode but becomes immediately available if a primary computer component fails, malfunctions or goes offline. It is an operative component and considered part of the working system. Hot spares can be power supplies, A/V switches, hard disk drives or network printers. The device is considered hot because it is turned on, although it is not continually active in the system.
A hot spare may be used for both hardware and software backup.
Techopedia explains Hot Spare
A hot spare is a failover component that offers reliability in system configurations. A failover occurs without user involvement and is generally automatic when system failure is detected. It acts like a secondary system that can be switched on if the primary system fails and is designed to rebuild automatically with little or no interruption.
A hot spare is typically a solitary, critical device that a computer needs in order to function. When there is a problem, the system is altered to incorporate the hot spare with its structure. It is intended as a temporary fix and designed to substantially increase system availability during the exchange process.
A hot spare also decreases the mean time of recovery for a device and prevents potential data loss due to disk failure. However, a hot spare does not provide 100 percent protection against momentary system loss when switching to the backup.