On Dec 15, 2007 6:51 AM, rihad <rihad@xxxxxxx> wrote: > http://www.postgresql.org/docs/8.3/static/wal-configuration.html > > Is it right that checkpoint_timeout means the amount of time up to which > you agree to lose data in the event of a power crash? No, dear god, no. :) Once something is committed, it won't be lost due to a server crash unless your hardware is lying about fsync. The data that hasn't been checkpointed has to be replayed upon a crash / restart, that's all. > What if I set it > to 1 hour (and bump checkpoint_segments accordingly), does it mean that > I'm willing to lose up to 1 hour of data? Nope, but it could take a very long time to recover from a crash / kill -9 situation as all that data gets replayed. > I'm thinking about increasing > checkpoint_timeout to mitigate the full_page_writes bloat. You'd be better off working on tuning the background writer so that you lose some small% of performance all the time but never have huge spike in checkpointing. > BTW how are transactions WAL logged? Do the logs include data too? In > this case, am I right that the effects of full_page_writes=on serve as a > starting data page on top of which to replay transactions when doing > crash recovery? full_page_writes = on = you CAN recover from a server crash / kill -9. Off not so much guaranteed. ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
