[Box Backup-dev] Userland RAID question

Chris Wilson boxbackup-dev at fluffy.co.uk
Fri Apr 21 10:39:31 BST 2006


Hi Martin,

On Fri, 2006-04-21 at 08:55 +0100, Martin Ebourne wrote:

> (the last disk is always the parity disk in RAID5).

Maybe I'm splitting hairs, but I don't think that's strictly true. The
parity in RAID 5 is divided between all the disks in a round-robin
fashion, to avoid one disk becoming the bottleneck for all writes. I
think that RAID 4 is where one disk holds all the parity.
[http://en.wikipedia.org/wiki/RAID5#RAID_5]

Nevertheless, the total capacity of the array is the same in both cases,
which is the sum of the sizes of n-1 disks.

Cheers, Chris.
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