Re: RAID Suggestion for webserver

[Bart-Jan Vrielink <bartjan@vrielink.net>]

On Sun, 2002-02-10 at 22:38, Jason Lim wrote:

> 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.
> 
> The question becomes... which provides more performance and is more
> reliable?

RAID10 will give you the most performance. Not only do you have 4 disks
working for you all the time, instead of 3 with RAID5, you (or more
accurate: your CPU) also don't have to calculate the parity which is
used by RAID5.

Both will survive a 1 disk crash with no problems and both will appear
as a RAID0 array when running in degraded mode. However, the reliability
is different when a second disk fails. In RAID5 with spare you are out
of luck when a second disk fails while the spare is rebuilding.
With RAID10 and 1 failed disk, you only have the disk that is in the
same stripe as the failed disk that is save to fail.
I'm not sure if the raid card supports a stripe of two mirrors. This
setup will survive a 2 disk failure.

-- 
Tot ziens,

Bart-Jan