On Tue, Mar 13, 2012 at 6:44 PM, Josh Berkus <josh@agliodbs.com> wrote:
>> That's a speedup of nearly a factor of two, so clearly fsync-related
>> stalls are a big problem here, even with wal_buffers cranked up
>> through the ceiling.
>
> Hmmmm. Do you have any ability to test on XFS?
It seems I do.
XFS, with fsync = on:
tps = 14746.687499 (including connections establishing)
XFS, with fsync = off:
tps = 25121.876560 (including connections establishing)
No real dramatic difference there, maybe a bit slower.
On further thought, it may be that this is just a simple case of too
many checkpoints. With fsync=off, we don't have to actually write all
that dirty data back to disk. I'm going to try cranking up
checkpoint_segments and see what happens.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company