Herve' > Hum ... it's only for speed aspect ... I was using postgresql with this > option since 7.01 ... and for me fsync=on was so slow ... > Is it really no time consuming for the system to bring it ON now with > v7.4.3 ??
Well, I wouldn't do it until you've figured out the current performance problem. The issue with having fsync=off is that, if someone yanks the power cord on your server, there is a significant chance that you will have to restore the database from backup becuase it will be corrupted. But clearly you've been living with that risk for some time. It *is* true that there is significantly less performance difference between 7.4 with fsync off and on than there was between 7.1 with fsync off and on. But there is still a difference. In 7.0 and 7.1 (I think), when you turned fsync off it turned WAL off completely, resulting in a substantial difference in disk activity. Now, it just stops checkpointing WAL but WAL is still recording -- meaning that disk activity decreases some but not a lot. The difference is more noticable the more vulnerable to contention your disk system is. The other reason not to think of fsync=off as a permanent performance tweak is that we're likely to remove the option sometime in the next 2 versions, since an increasing number of features depend on WAL behavior, and the option is largely a legacy of the 7.0 days, when WAL was sometimes buggy and needed to be turned off to get the database to start. -- Josh Berkus Aglio Database Solutions San Francisco ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster