Tom,
> When you get right down to it, what we use fsync for is to force write
> ordering --- Unix kernels do not guarantee write ordering any other way.
> We use it to ensure WAL records hit disk before data file changes do.
>
> Bottom line: I wouldn't run with fsync off in a mission-critical
> database. If you're prepared to accept a risk of having to restore from
> your last backup after a system crash, maybe it's okay.
Thanks for that overview. Sadly, even with fsynch on, I was forced to restore
from backup because the data needs to be 100% reliable and the crash was due
to a disk lockup on a checkpoint ... beyond the ability of WAL to deal with,
I think.
One last, last question: I was just asked a question on IRC, and I can't find
docs defining fsynch, fdatasynch, opensynch, and opendatasynch beyond section
11.3 which just says that they are all synch methods. Are there docs?
--
-Josh Berkus
Aglio Database Solutions
San Francisco
