I would recommend running a bonnie++ benchmark on your array to see if it's the array/controller/raid being crap, or wether it's postgres. I have had some very surprising results from arrays that theoretically should be fast, but turned out to be very slow.
I would also seriously have to recommend against a 14 drive RAID 5! This is statisticaly as likely to fail as a 7 drive RAID 0 (not counting the spare, but rebuiling a spare is very hard on existing drives).
Thanks for the reply.
Here are the results of the bonnie test on my array:
./bonnie -s 10000 -d . > oo 2>&1
File './Bonnie.23736', size: 10485760000
Writing with putc()...done
Rewriting...done
Writing intelligently...done
Reading with getc()...done
Reading intelligently...done
Seeker 1...Seeker 2...Seeker 3...start 'em...done...done...done...
-------Sequential Output-------- ---Sequential Input-- --Random--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
10000 4762 96.0 46140 78.8 31180 61.0 3810 99.9 71586 67.7 411.8 13.1On a different note, I am not sure how the probability of RAID5 over 15 disks failing is the same as that of a RAID0 array over 7 disks. RAID5 can operate in a degraded mode (14 disks - 1 bad), RAID0 on the other hand cannot operate on 6 disks (6 disks - 1 bad). Am I missing something?
Are you saying running RAID0 on a set of 2 RAID1 arrays of 7 each? That would work fine, except I cannot afford to "loose" that much space.
Care to comment on these numbers? Thanks.
Arshavir
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