On Tuesday 13 July 2004 15:11, Maximilian Wilhelm wrote: > * If all disc have the same size > size(RAID) = (n - 1 / n) * disc size. > * If one disc failes, replace it and be happy.
3.75 * 36 = 135 GB is what I get - this means that an array of 4 discs reserves 1/4 of its size each? > > So you would have ~108GB useable space. Mh, I'll check the formula, with 5 discs, it is said that you pay 20% more that you get. What I read is that the parity blocks take alltogether only the size of one disk, hence I'd calculate that with 4 disks 25 % are used for parity, leaving 3 x 38 = 108 GB which had been your result :) Is the formula maybe (n - 1) * disk size? Regards Ralf