Re: 3ware 9650 issues

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On Sun, 22 Jun 2008 at 1:01am, Ruslan Sivak wrote

Joshua Baker-LePain wrote:
On Sat, 21 Jun 2008 at 9:12pm, John R Pierce wrote

I have no experience with that raid card, most of our larger systems use external SAN storage, but I will say that, IMHO, is a very large raid-6. we usually don't make single raid sets much large than 7-8 drives, and for a very large storage system, will stripe multiple raid5/6 sets rather than have one huge one.

Would that I had such luxuries. This is a university lab with needs for massive amounts of data and not much money with which to do it.

Wouldn't striping a bunch of raid6 volumes give you about the same amount of space?

No.  We have 24 drives.  Use one for a hot spare -> leaves 23.

1 array:  23 drives, - 2 for parity -> capacity = 21 * drive capacity
2 arrays: array1 = 12 drives - 2 for parity -> 10 drives
          array2 = 11 drives - 2 for parity -> 9 drives
                                    -> capcity = 19 * drive capcity
3 arrays: array1 = 8 drives - 2 for parity -> 6 drives
          array2 = 8 drives - 2 for parity -> 6 drives
          array3 = 7 drives - 2 for parity -> 5 drives
                                    -> capcity = 17 * drive capacity

With 1TB drives, you're losing 2TB worth of volume space for each increased number of arrays. That's a lot of space.

Unless I misunderstood you...

--
Joshua Baker-LePain
QB3 Shared Cluster Sysadmin
UCSF
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