RAID
RAID can protect uptime. RAID levels 1, 0+1/10, 5 and 6 (and their variants such as 50 and 51) make up for a mechanical hard disk failure. Even after the disk failed, the data on the array can still be used. Instead of a time consuming restore from tape, DVD or other slow backup media, RAID allows data to be restored to a replacement disk from the other members of the array. During this restoration process, it is available to users in a degraded state. This is very important to enterprises, as downtime quickly leads to lost earning power. For home users, it can protect uptime of large media storage arrays, which would require time consuming restoration from dozens of DVD or quite a few tapes in the event of a disk failing that is not protected by redundancy.