RAID - Redundent Array of Independent / Inexpensive Disks
Takes multiple hard drives and does either:
RAID 0 - Uses them as one drive, writing half data to each drive for THEORETICAL twice the drive read / write speed. (if you have 2x 20gb HDs, you get full 40gbs)
RAID 1 - Mirrors the data on the first drive to the second, so if one drive dies, you don't loose any data. (if you have 2x 20gb hard drives, you only get to use 20gb of it)
RAID 5 - Mirrors AND Stripes data, plus uses some other thing, I THINK it needs 5 drives, but you get the space of only two of them.
RAID is usually a server kinda thing, and is not usually worth the cost for the average joe.
ECC RAM - Error Checkign RAM, used in servers to find and fix errors in RAM, pretty useless in anythign BUT a server. Basically uses an extra few bits on the RAM chip to verify data.
