On Mon, 11 Feb 2002, Jason Lim wrote: > Disk space is not a major consideration: this is not a fileserver. It is a > webserver, so we're looking at more sporadic random small file reads. I > know its not likely to happen (that is, that more than 1 disk dies at a > time), but I want to get the server pretty much "remote controlled" even > in the event of disaster.
ahh, ok - I was assuming a distributed serving system for some reason... > Okay, as you said, with RAID10 and 4 40G HDs, usable space is 80Gs. > > On the other hand, with RAID5 and 3 40G HDs, usable space is also 80Gs, > with 1 spare HD for rebuilding. err, unless I'm mistaken: RAID10: mirrored system = total/2 = 80 striped system = single * 2 = 80 combined that gives you a mirrored & striped "drive". this gives you 80GB total RAID5: the "spare" is distributed over all of the disks...in the case of 4 disks, one of the disks can be thought of as a spare, which leaves you with 3 * 40 = 120 GB. depending on the failure type, this is your outcome: RAID10: lose 1 drive - you're ok, 'cus you can reconstruct it from the mirror lose 2 drives - depends on which drives...if it's the identical one on the mirrored side, you're screwed. if it's the opposing one, you can reconstruct from the mirror (all the while your whole system is down unless the striped setup can use the left-over drive that's not damaged). RAID5: lose 1 drive - you're ok, 'cus you can reconstruct it from the other drives lose 2 drives - you're screwed. So if storage space is not an concern, I guess RAID10 would be your best bet. > The question becomes... which provides more performance and is more > reliable? the raid10 from the looks of it... -lev
