Multiple Hard Drives Working Together: All about RAIDs

PC World - Stevey, admitted confused by the benefits of RAIDs, asked the Answer Line forum to explain these hard drive groups.

A Redundant Array of Independent Disks (RAID) puts multiple hard drives together to improve on what a single drive can do on its own. Depending on how you configure a RAID, it can increase your computer's speed while giving you a single "drive" that can hold as much as all of the drives combined. Or you can use a RAID to increase reliability, so that your computer will keep working after a hard drive crash. Some RAIDS allow you to do both.

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Here are three of the most popular RAID configurations:

RAID 0

This type of RAID turns the two or more drives inside of it into one bigger, faster storage unit. But it significantly increases the odds of a crashed drive taking all of your files with it.

When you save a file, a RAID 0 splits it into sections and distributes it across the various drives. Since all of the drive heads are working together on different parts of the same file, the array can write and read much faster than a single drive.

It also gives you a lot of storage. If you've got four 1TB drives in a RAID 0 array, you effectively have a single 4TB drive.

But those four drives quadruple the likelihood that one of them will crash. And because every file is distributed across all of the drives, if one drive crashes, you lose everything.

RAID 1

Turn two 1TB drives into a RAID 1 array, and you get the capacity and speed of a single 1TB drive. So what's the point? Protection.

In a RAID 1 array, the two drives mirror each other, so that they both contain the exact same data. If one drive fails, the other keeps working. No files are lost, and there's no downtime.

But don't confuse RAID 1 with a real backup. A hard drive crash isn't the only disaster that can destroy your files. If a fire, burglar, Trojan, or bad mistake on your part hits one one of those drives, it will likely hit the other.

RAID 5

Here you can get the benefits of RAID 0 and RAID 1: capacity, speed, and protection. But you'll need at least three drives, and only two of those three will be used for storage.

Like RAID 0, a RAID 5 array breaks data into sections that are stored on two or more drives, resulting in increased speed and capacity. But it devotes one additional drive to parity, saving information on the other drives' information.

If one of the non-parity drive dies, the parity drive can look at what's on the working drive (or drives), and calculate what would have been on the dead one. The RAID and the computer will continue to work, although the extra calculations will slow things down.

Read the original forum discussion.

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