Also, RAID10 wastes half of your space (need to buy twice as many drives, doubling costs instantly), and while RAID5 isn't as wasteful in terms of disk space, it eats a lot of CPU power (slows down your computer), unless you bought a very expensive "hardware" RAID controller (the kind with a beefy processor doing the XOR'ing onboard -- hundreds of $$$ for something nice). Yeah, I'm a 3ware or nothing kinda guy.