Use RAID 1 for your OS. It is fault tolerant. You lose the hard drive to failure, you have a spare to move or repoint your boot.ini file. RAID 0 is not fault tolerant. You lose one drive, say bye bye ...
Suppose you have a system that has RAID0 with 2 disks. This is used for an internal proxy, something like Squid, but take any RAID0 use for this question. Disk #1 goes bad, hosing the system, and ...