Re: fsync = true beneficial on ext3?

Actually, I don't think even that is a valid test. The absence of a
failure doesn't mean one can't occur in this case. Doesn't matter if you
try the test 1 or 10,000 times; the test will only be conclusive if you
actually see a failure.

On Mon, Feb 09, 2004 at 10:19:15AM -0700, scott.marlowe wrote:
> On Sun, 8 Feb 2004, 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?
> >
> > 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?
>
> With all the other posts on this topic, I just want to point out that it's
> all theory until you build your machine, set it up, initiate a hundred or
> so parallel transactions, and pull the plug in the middle.
>
> Without pulling the plug, you just don't know for sure.  And you need to
> do it a few times, in case your machine "got lucky" once and might fail on
> subsequent power fails.
>
>
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--
Jim C. Nasby, Database Consultant                  jim@nasby.net
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