RAID

[Charles Steinkuehler]

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Luke-Jr wrote:
> So anyway... what's the pros/cons of the various RAID configurations possible 
> with 8 of 18 GB HDs? ;)
> Any reason to use RAID 5+0 over just RAID 5? At first glance, while 5+0 allows 
> loss of two disks, that only appears to be the case if both disks are in a 
> separate set of 4. If there's two disks failing, wouldn't that be a 50:50 
> chance on 5+0 being ok, or being dead? Is it worth the 18 GB to get that 
> 50:50 chance?

If you're thinking about RAID 5+0 (presumably dual 4-disk RAID 5 sets),
just run one RAID5 array with 7 disks, and leave the eighth as a
hot-spare.  You can still sort-of loose two disks (as long as they don't
both go within a RAID rebuild time of each other...much better odds than
your 5+0), and you get an extra 18 Gig of drive space.

If you're a bit more nervous about your drives, you could always go with
a RAID 10 setup (dual 4-disk RAID0 stripes, mirrored together).  You
could loose up to 4 disks that way, but it wastes a lot of space.

I'd personally go with a 6 or 7 disk RAID5 and leave 1 or 2 disks as hot
spares.

NOTE: There can be performance issues when doing RAID5, but with 18G
drives, I suspect the limit on system performance will be your disks
(even with 8 of them), rather than calculating parity...might not hurt
to run some tests, however.

- --
Charles Steinkuehler
charles at steinkuehler.net
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