Re: wal_buffers, redux

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