Andrew McMillan wrote:
> On Thu, 2004-04-08 at 14:13, Tom Lane wrote:
> > Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > > Tom Lane wrote:
> > >> But it should be okay to set the filesystem to journal only its own
> > >> metadata. There's no need for it to journal file contents.
> >
> > > Can you set ext2 to journal metadata? I didn't know it could do that.
> >
> > No, ext2 has no journal at all AFAIK. But I believe ext3 has an option
> > to journal or not journal file contents, and at least on a Postgres-only
> > volume you'd want to turn that off.
>
> No, it certainly doesn't.
>
> To be honest I was not aware that PostgreSQL was susceptible to failure
> on non[metadata] journalled filesystems - I was [somewhat vaguely] of
> the understanding that it would work fine on any filesystem.
We expect the filesystem to come back intact. If it doesn't from an
ext2 crash, we can't WAL recover in all cases.
> And obviously, from my original post, we can see that I believed
> metadata journalling was wasted on it.
No. UFS file systems don't do journaling, but do metadata fsync, which
is all we need.
> Is the 'noatime' option worthwhile? Are you saying that PostgreSQL
noatime might help, not sure, but my guess is that most inode fsync's
are modifications of mtime, which can't be turned off with amount
option.
> should always be run on a metadata journalled filesystem then, and that
> VFAT, ext2, etc are ++ungood?
Yep. Not sure about VFAT but we do need the filesystem to return after
a crash, obviously, or we can't even get to the xlog directory or the
/data files to do WAL recovery.
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
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