Andres Freund <and...@anarazel.de> writes: > On Friday 05 November 2010 19:13:47 Tom Lane wrote: >> If open_dsync is so bad for performance on Linux, maybe it's bad >> everywhere? Should we be rethinking the default preference order?
> I fail to see how it could be beneficial on *any* non-buggy platform. > Especially with small wal_buffers and larger commits (but also otherwise) it > increases the amount of synchronous writes the os has to do tremendously. > * It removes about all benefits of XLogBackgroundFlush() > * It removes any chances of reordering after writing. > * It makes AdvanceXLInsertBuffer synchronous if it has to write outy > Whats the theory about placing it so high in the preferences list? I think the original idea was that if you had a dedicated WAL drive then sync-on-write would be reasonable. But that was a very long time ago and I'm not sure that the system's behavior is anything like what it was then; for that matter I'm not sure we had proof that it was an optimal choice even back then. That's why I want to revisit the choice of default and not just go for "minimum" change. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers