Re: fsync = true beneficial on ext3?

Would a battery backed Card do the trick?




On Tuesday 10 February 2004 00:42, Bruce Momjian wrote:
> Ed L. wrote:
> > I'm curious what the consensus is, if any, on use of fsync on ext3
> > filesystems with postgresql 7.3.4 or later.  I did some recent
> > performance tests demonstrating a 45%-70% performance improvement for
> > simple inserts with fsync off on one particular system.  Does fsync =
> > true buy me any additional recoverability beyond ext3's journal recovery?
>
> Yes, it does.  Without fsync, you can't be sure the data has been pushed
> to the disk drive in case of an OS crash or power failure.
>
> > If we write something without sync'ing, presumably it's immediately
> > journaled?  So even if the DB crashes prior to fsync'ing, are we fully
> > recoverable?  I've been running a few pgsql clusters on ext3 with fsync =
> > false, suffered numerous OS crashes, and have yet to lose any data or see
> > any corruption from any of those crashes.  Have I just been lucky?
>
> The fsync makes sure it hits the drive, rather than staying in the
> kernel cache during an OS failure.