Definition of HOT SPARE in Network Encyclopedia.
What is Hot Spare?
A hot spare is a backup component that can be placed into service immediately when a primary component fails, without needing to shut down all system.

The term HOT is an adjective referring to actions that can be performed on systems or hardware devices while the power for the device is still turned on or while the device still has a live network connection or telecommunications link.
“Hot” technologies are used in:
- Fault-tolerant disk drive systems such as RAID systems
- Redundant power supply systems
- Modular Ethernet switches and routers
- Redundant high-speed data communication links
Examples of disk storage systems that use “hot” technologies include the following:
- Hot-rebuild system: A drive subsystem that can automatically rebuild its original drive configuration after drive failure
- Hot-spare system: A drive subsystem that has additional unused drives that can be called into action when drive failure occurs
- Hot-swap system: A drive subsystem in which drives are mounted on trays and can be removed and replaced without shutting down the system
TIP
When you buy a hardware RAID unit, be sure that it has hot-rebuild, hot-spare, and hot-swap capabilities.