> The general question is - does PostgreSQL really need fsync? I suppose it
> is a question for design, not platform-specific one. It sounds like only
> one scenario, when fsync is useful, is to interprocess communication via
> open file. But PostgreSQL utilize IPC for this, so does fsync is really
> required?
NO!
Fsync is so that when your computer loses power without warning, you
will have no data loss.
If you turn it off, you run the risk of losing data if you lose power.
Chris