What are RAID Levels? – Redundant Array of Independent Disks

RAID – or Redundant Array of Independent Disks – comes in different flavours from RAID 0 and RAID 1 to combination of those two, and going up to RAID 5 and RAID 10.
You can use either IDE, Serial ATA or SCSI disks in RAID configurations, but not a mixture of any of them.
Some basics for RAID levels:
RAID 0
RAID 0 is simply the combination of two or more hard disks to appear to the computer as one large hard disk. It’s also called striping. You could take two 250 GB hard disks, set them up as RAID 0 and the PC will see them as a single 500 GB hard disk. Once that is configured and setup for all practical purposes the PC will behave like there is only one 500 GB hard disk in the machine.
The main advantage of striping is the extra speed that you will get. Writing to hard disks is the bottleneck in most modern PCs. However with RAID 0 the writing is split across two drives, and the PC is writing simultaneously to both; that does speed things up. You won’t get 100% speed increases but 20-30% is quite possible.
The main disadvantage is that there is double the risk of a hard disk failure. You need only one of your two drives to go faulty and you’ve lost all your data.
RAID 1
RAID 1, also called mirroring, is setting up the two disks such that the second one mirrors the first providing you an up to the minute backup if something ever goes wrong with the first disk. Should the first hard disk fail you simply remove it, put the second disk in it’s place and carry on where you left off.
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RAID Levels in Depth:
http://www.acnc.com/04_01_00.html