On Friday 04 June 2010 15:59:05 Tom Lane wrote: > Marc Cousin <cousinmarc@xxxxxxxxx> writes: > > I hope I'm not going to expose an already known problem, but I couldn't > > find it mailing list archives (I only found > > http://archives.postgresql.org/pgsql- hackers/2009-12/msg01543.php). > > You sure this isn't the well-known "ext4 actually implements fsync > where ext3 didn't" issue? I doubt it. It reads to me like he is testing the two methods on the same installation with the same kernel > > with wal_sync_method = open_datasync (new default) > > marc=# INSERT INTO test SELECT generate_series(1,100000); > > INSERT 0 100000 > > Time: 16083,912 ms > > > > with wal_sync_method = fdatasync (old default) > > > > marc=# INSERT INTO test SELECT generate_series(1,100000); > > INSERT 0 100000 > > Time: 954,000 ms Its not actually surprising that in such a open_datasync is hugely slower than fdatasync. With open_datasync every single write will be synchronous, very likely not reordered/batched/whatever. In contrast to that with fdatasync it will only synced in way much bigger batches. Or am I missing something? I always thought the synchronous write methods to be a fallback kludge and didnt realize its actually the preferred method... Andres -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
