Hot Spare and Hot Swapping
Hot spares gives system administrators the ability to quickly recover from component failureanother mechanism to deal with component failure. In a common use, a hot spare enables a RAID system to automatically failover to a spare hard drive should one of the other drives in the RAID array fail. A hot spare does not require any manual interventionrather, a redundant drive resides in the system at all times, just waiting to take over if another drive fails. The hot spare drive will take over automatically, leaving the failed drive to be removed at a later time. Even though hot-spare technology adds an extra level of protection to your system, after a drive has failed and the hot spare has been used, the situation should be remedied as soon as possible.
Hot swapping is the ability to replace a failed component while the system is running. Perhaps the most commonly identified hot-swap component is the hard drive. In certain RAID configurations, when a hard drive crashes, hot swapping allows you simply to take the failed drive out of the server and install a new one.
The benefits of hot swapping are very clear in that it allows a failed component to be recognized and replaced without compromising system availability. Depending on the system's configuration, the new hardware will normally be recognized automatically by both the current hardware and the operating system. Nowadays, most internal and external RAID subsystems support the hot-swapping feature. Some hot-swappable components include power supplies and hard disks.