RAID = Redundant Array of Independent Disks (Originally it was Redundant Array of Inexpensive Disks... anyway)
Basically it's a way to store data into mutiple harddisks. There are many types of RAID functions, here I'll just list few ones that are most commonly seen.
1. RAID 0: Also known as disk striping. This type offers the best peformance. Basically it interleaves two or more HDs so that they act as one single HD. Data would be stored and managed collectively in these drives as a single unit. Doing so can greatly reduce access time and to achieve highest possible sustained data transfer rate. You can think of it as two hardrives are now combined as one single drive. Datas are actually stored in the two actual drives. But since we can access two hardrives to get/store data, less access time would be needed for a transaction. However, if one of the drives in RAID 0 is broken, you would lose all the data. (ie, no fault tolerance.)
2. RAID 1: This type is also known as Disk Mirroring. Basically it still consists of two or more disks. But now the data would be duplicated into each of the disk drive. The result is that your data will be completely backed-up. (ie, best fault tolerance.) Also, the READ performance would increace, since each of the disks could be read at the same time. But WRITE performance would stay the same as single-drive.
3. RAID 0+1: It combines RAID 0 & 1. You need at least 4 harddisks for this type of RAID. Basically it has features from both RAID 0 & 1. It offers the best performance along with the best data safety.
The above 3 types can be commonly seen these days. Usually when you see a motherboard with RAID capability, it means that the board support these 3 types of RAID. There are, of course, other types. But I think I'll stop right here (so that you will not feel bored...)
Hope this would help.... and if I said anything incorrect... please correct me...
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