RAID was one way of getting around this and using more than four total devices. Before huge drives, RAID 0 was often used to increase capacity for digital imaging storage. Kind of stupid, when some of the Sun systems were already available. I did that on my old Win 95 box. Raid was the only way I had to have eight (12 gig! hahaha) drives at hand.
I have always had more music files than I knew what to do with.
It was stupid, but it worked. This doesn't, yet.
There have to be other ways of
simulating a single drive. I mean,
even RAID-0's supposed to have
redundancy.
I know very little about big server arrays, but I do know that my old board had onboard RAID 0 or RAID 1 and you could set your drives up for either redundancy and security using their RAID 1 functions, but the drives all had to be identical ... or you could use any array of mismatched drives (which I had laying around) in RAID 0 but there was no security. It was only a way to increase capacity in that function. In fact files were sometimes fragmented across every drive. There are much better ways to do this, but that offered a poorboy option to increase storage and since they worked in two-in-parallel it increased delivery rates at the same time.
Obviously if I had more money and really needed "Speed" in those days there were much better options, but I had that option, almost by accident, so I used it.