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

Alex Turner

On Fri, 11 Mar 2005 16:13:05 -0500, Arshavir Grigorian <[EMAIL PROTECTED]> 
> Hi,
> I have a RAID5 array (mdadm) with 14 disks + 1 spare. This partition has
> an Ext3 filesystem which is used by Postgres. Currently we are loading a
> 50G database on this server from a Postgres dump (copy, not insert) and
> are experiencing very slow write performance (35 records per second).
> Top shows that the Postgres process (postmaster) is being constantly put
> into D state for extended periods of time (2-3 seconds) which I assume
> is because it's waiting for disk io. I have just started gathering
> system statistics and here is what sar -b shows: (this is while the db
> is being loaded - pg_restore)
>                tps        rtps     wtps      bread/s  bwrtn/s
> 01:35:01 PM    275.77     76.12    199.66    709.59   2315.23
> 01:45:01 PM    287.25     75.56    211.69    706.52   2413.06
> 01:55:01 PM    281.73     76.35    205.37    711.84   2389.86

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