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Redundant Arrays of Inexpensive Disks (RAID)

Most of the reliability features and issues discussed in this part of the site relate to making drives themselves more reliable. However, there is only so much you can do to improve the reliability of a single drive without the cost becoming exorbitant. Furthermore, since most people aren't willing to pay for ultra-reliable drives, manufacturers have little incentive to develop them. For those applications where reliability is paramount, the quality of no single-drive solution is sufficient. For these situations, many businesses and power users are increasingly turning to the use of multiple drives in a redundant or partially-redundant array configuration. The common term that refers to this technology is Redundant Arrays of Inexpensive (or Independent) Disks, abbreviated RAID.

The principle behind RAID is "belt and suspenders": if you store redundant information across multiple disks, then you insulate yourself from disaster in the event that one of the disks fails. If done properly, you also improve performance--sometimes in a substantial way--by allowing the drives to be accessed in parallel. And you can make it so bad drives can be replaced without the system even being taken down.

RAID is a big topic unto itself; there are many different ways that RAID can be implemented; various hardware and software considerations; and many tradeoffs to be considered when implementing a system. I have therefore created a separate area that discusses RAID in detail. Check it out if the subject interests you. RAID is rapidly increasing in popularity, and I believe it will only be a few years before it starts showing up even in high-end home systems.

Next: Hard Disk Warranty and Disaster Recovery Issues

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