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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@steinkuehler.net