Re: Perfomance Tuning

On Tue, 12 Aug 2003, Neil Conway wrote:

> On Tue, Aug 12, 2003 at 12:52:46AM -0400, Bruce Momjian wrote:
>  I don't use Linux and was just repeating what I had heard from others,
> > and read in postings.  I don't have any first-hand experience with ext2
> > (except for a laptop I borrowed that wouldn't boot after being shut
> > off), but others on this mailing list have said the same thing.
>
> Right, and I understand the need to answer users asking about
> which filesystem to use, but I'd be cautious of bad-mouthing
> another OSS project without any hard evidence to back up our
> claim (of course if we have such evidence, then fine -- I
> just haven't seen it). It would be like $SOME_LARGE_OSS
> project saying "Don't use our project with PostgreSQL, as
> foo@bar.org had data corruption with PostgreSQL 6.3 on
> UnixWare" -- kind of annoying, right?

Wow, you put my thoughts exactly into words for me, thanks Neil.

> > > (a) ext3 does metadata-only journalling by default
> >
> > If that is true, why was I told people have to mount their ext3 file
> > systems with metadata-only.  Again, I have no experience myself, but why
> > are people telling me this?
>
> Perhaps they were suggesting that people mount ext2 using
> data=writeback, rather than the default of data=ordered.
>
> BTW, I've heard from a couple different people that using
> ext3 with data=journalled (i.e. enabling journalling of both
> data and metadata) actually makes PostgreSQL faster, as
> it means that ext3 can skip PostgreSQL's fsync request
> since ext3's log is flushed to disk already. I haven't
> tested this myself, however.

Now that you mention it, that makes sense.  I might have to test ext3 now
that the 2.6 kernel is on the way, i.e. the 2.4 kernel should be settling
down by now.