Re: Would it be OK if I put db file on a ext2 filesystem?

On Dec 12, 2007 9:46 AM, Collin Kidder <adderd@kkmfg.com> wrote:
> Magicloud Wang wrote:
> > Dear,
> >       I think database has its own operation journal, and different journal
> > filesystem does give different performance. So if I put database file on a
> > non-journal filesystem, would it be safe? Does this like using a raw device?
> >
> >
> >
> You lose a little bit of data integrity in exchange for a little bit of
> speed. I suppose it'd be a fine thing to do so long as you can live with
> that trade off. If you want good data integrity you are more likely to
> get it from battery backed RAID5 or RAID10 or something of that sort
> rather than just trusting something like EXT3 or Reiser. EXT2 isn't a
> bad file system.

It's one of things where the known bugs in ext2/3 aren't as bad as
they sound, while the unknown bugs in some newer, less tested file
systems are often worse.  OTOH, ext2/3 do have a 2 TB partition size
limit (or at least used to) so for some things, you just gotta go to a
different file system.

Back to the subject at hand, do you need journaling for the db, this
thread from last year has a lot of good info in it.  It's the one
where I got the impression that ext2 for pg_xlog was fine and dandy.
I remember now, after reading it, that certain types of fsync might be
dangerous with non-journaled file systems.

http://archives.postgresql.org/pgsql-performance/2006-08/msg00101.php