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

[Ralf Gesellen'setter <rgx@gmx.de>]

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