Re: Q: Hard Disc Layout for Tjener? (Raid)
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?