Re: win32 performance - fsync question

Evgeny Rodichev wrote:
> There are two different concerns here.
> 
> 1. transactions loss because of unexpected power loss and/or system failure
> 2. inconsistent database state
> 
> For many application (1) is fairly acceptable, and (2) is not.
> 
> So I'd like to formulate my questions by another way.
> 
> - if PostgeSQL is running without fsync, and power loss occur, which kind
> of damage is possible? 1, 2, or both?

Both. If 1 can happen then 2 can happen.

> - it looks like with proper fwrite/fflush policy it is possible to
> guarantee that only transactions loss may occur, but database
> keeps some consistent state as before (several) last transactions.
> Is it true for PostgeSQL?

No - if fsync is on and the transaction is reported as committed then it 
should still be there when the power returns. Provided you don't suffer 
hardware failure you should be able to rely on a committed transaction 
actually being written to disk. That's what fsync does for you.

--  Richard Huxton  Archonet Ltd