On Monday 05 Sep 2011 22:23:32 Scott Marlowe wrote: > On Mon, Sep 5, 2011 at 11:24 AM, Andres Freund <andres@xxxxxxxxxxx> wrote: > > On Monday, September 05, 2011 14:57:43 Richard Shaw wrote: > >> Autovacuum has been disabled and set to run manually via cron during a > >> quiet period and fsync has recently been turned off to gauge any real > >> world performance increase, there is battery backup on the raid card > >> providing some level of resilience. > > > > That doesn't help you against a failure due to fsync() off as the BBU can > > only protect data that actually has been written to disk. Without > > fsync=on no guarantee about that exists. > > Further, if you've got a bbu cache on the RAID card the gains from > fsync=off wll be low / nonexistent. Thats not necessarily true. If you have a mixed load of many small writes and some parallel huge writes (especially in combination with big indexes) fsync=off still can give you quite big performance increases. Even in the presenence of synchronous_commit=off. Andres -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
