Redundant array of independent disks

In computing, a redundant array of independent disks (more commonly known as a RAID) is a system of using multiple hard drives for sharing or replicating data among the drives. Depending on the version chosen, the benefit of RAID is one or more of increased data integrity, fault-tolerance, throughput or capacity compared to single drives. In its original implementations (in which it was an abbreviation for "Redundant Array of Inexpensive Disks"), its key advantage was the ability to combine multiple low-cost devices using older technology into an array that offered greater capacity, reliability, or speed, or a combination of these things, than was affordably available in a single device using the newest technology.

Related Topics:
Computing - Hard drive - Data - Data integrity - Fault-tolerance - Throughput

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At the very simplest level, RAID combines multiple hard drives into one single logical unit. Thus, instead of seeing several different hard drives, the operating system sees only one. RAID is typically used on server computers, and is usually implemented with identically-sized disk drives. With decreases in hard drive prices and wider availability of RAID options built into motherboard chipsets, RAID is also being found and offered as an option in more advanced end user computers. This is especially true in computers dedicated to storage-intensive tasks, such as video and audio editing.

Related Topics:
Operating system - Server - Motherboard

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The original RAID specification suggested a number of prototype "RAID levels", or combinations of disks. Each had theoretical advantages and disadvantages. Over the years, different implementations of the RAID concept have appeared. Most differ substantially from the original idealized RAID levels, but the numbered names have remained. This can be confusing, since one implementation of RAID 5, for example, can differ substantially from another. RAID 3 and RAID 4 are often confused and even used interchangeably.

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The very definition of RAID has been argued over the years. The use of the term redundant leads many to split hairs over whether RAID 0 is a "real" RAID type. Similarly, the change from inexpensive to independent confuses many as to the intended purpose of RAID. There are even some single-disk implementations of the RAID concept. For the purpose of this article, we will say that any system which employs the basic RAID concepts to recombine physical disk space for purposes of reliability, capacity, or performance is a RAID system.

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