What Is RAID?

RAID (for redundant arrays inexpensive disks) hooks up several arrays of relatively small disks in parallel to do the job of a larger disk. The disks are separated from the system unit in a cabinet that, because it comprises a sophisticated system wthin the computer system, is often referred to as the disk subsystem. The subsystem is set up to record redundant copies of information so that, in the event of a system crash, the redundant data can be used to reconstructed the lost data. Computer systems define several different levels of RAID.

In the most expensive known as RAID Level 1 a backup disk pack corresponds to each production disk pack. If any production pack fails, its backup immediately takes over.Level 1 RAID is swappable, meaning that a defective pack can be taken offline for repair and replaced without even turning the power off. Duplicating the entire contents of a disk on another disk in this manner is sometimes described as disk mirroring. If the disk system crashes, any lost data can be reconstructed from the contents of the parity disks.

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