Actualy my statistics were off a bit I realised - chance of failure for one drive is 1 in X. change of failure in RAID 0 is 7 in X, chance of one drive failure in 14 drive RAID 5 is 14 in X,13 in X for second drive, total probably is 182 in X*X, which is much lower than RAID 0.
Your drive performance is less than stellar for a 14 drive stripe, and CPU usage for writes is very high. Even so - this should be enough through put to get over 100 rows/sec assuming you have virtualy no stored procs (I have noticed that stored procs in plpgsql REALLY slow pg_sql down). Alex Turner netEconomist On Mon, 14 Mar 2005 15:54:34 -0500, Arshavir Grigorian <[EMAIL PROTECTED]> wrote: > Alex Turner wrote: > > 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 13.1 > > On 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 > ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])