Re: fsync = true beneficial on ext3?

JM wrote:
> Would a battery backed Card do the trick?

No because the fsync causes the data to hit the card. Without the
fscync, the data could remain only in the kernel cache.

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> 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.
>

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