RAID 0 would be the fastest ( & not a true RAID array ) The problem is that if only one of the two H.D.'s fails it corrupts all the data because it splits half to one drive & half to the other when storing.
The other set-up's are redundant which is what RAID is all about. If you think about it, in theory RAID 0 set-up is twice as likely to fail as a single hard drive because there are two of them with unique information. So you take the T.T.F. ( time to failure ) or M.T.B.F. ( mean time between failure ) & multiply the number of H.D.'s running....you will eventually reach a number where immediate failure of at least one of them wll occur. I think the estimated T.T.F. of the average H.D. is something like 80,000 start/stop cycles. In other words if you used 80,000 hard drives with 80,000 start/stop cycles all at the same time; theoretically you should have an instant failure on at least one. Of course that's not entirely accurate because that's based on overall wear, but you get the idea.
That being said, one hard drive has all the unique information on it too, so unless you inted to do a true RAID set-up, you're taking a similar risk by running only one hard drive as you are running two....the total loss of all your information, it's just theoretically more likely with two of them. And we all know brand new stuff can fail instantly with no wear at all.
