Protecting your data with RAID

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© December 2005 Tony Lawrence

It is simply wonderful how inexpensive RAID has become. The RAID controller reviewed at http://www.macsimumnews.com sells for $299.00 and prices are still coming down.

That review concentrates on tech specs and performance, but here I'd like to talk about the other reason you want RAID: data protection. RAID means "Redundant Array of Inexpensive Disks" and it's the "redundant" part that I'm talking about. The simplest RAID is RAID-0 or mirroring, which simply writes the same data to two or more disks. If your primary disk failed, the mirror could take over and have no loss of data. RAID-5, which is the other most popular RAID configuration, spreads data over multiple disks and keeps the ability to reconstruct data from any single drive loss "on the fly" - in other words, a disk dies but your system keeps running (a little more slowly), and when you replace the failed drive, everything gets rebuilt and you are back to full protection again.

If performance is an issue, seek professional advice before implementing RAID. RAID 5 can provide very fast reads, but is slower at writing data. In some applications, that's fine: most of the access is just reading and there's very little updating. But other circumstances might be far better off with mirroring.

RAID does not replace backup. It doesn't prevent or allow recovery from accidental deletion or software glitch. It won't protect from malfunction of RAM or the computer's motherboard. I sometimes find people who think that RAID-0 (mirroring) does that; it does not: bad data is written to all disks in the mirror set at the exact same time, so everything is removed or corrupted at once. Do not neglect backup!

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