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Using 8mb cache Hard disks in RAID arrays does not speed it up that much compared to 2mb cache Hard disks. By themselves, they do perform a little better though..
RAID (Reduntant Array of Inexpensive Disks) is a way of making a set of hard drives look like a single disk on a computer.
There are a few types, the 2 popular ones for desktop systems are:
RAID 0 "Striping"
- Gets 2 (or more) identical disks and formats them as one disk. two 80 Gb disks look like one 160 Gb disk, for example. The data is shared equally through the array, by "Striping" the data. One chunk goes to one hard drive, the next chunk goes to the other, and it interleaves. RAID 0 arrays are very fast, and mine did 55 Mb/second on a good day. If one hard drive breaks, you lose ALL the data.
RAID 1 "Mirroring"
- Takes 2 disks and copies the data identically to both hard drives. Two 80Gb drives look like an 80Gb disk in Explorer. If one drive breaks, the other takes over and you keep the data. Used when data is very important.
There are other types as well: 3, 5, 0+1...
If you decide on a RAID 0 array, backup and store the important data. RAID 0 is fast but a little less reliable..