Re: WAL sync behaviour

Steinar H. Gunderson wrote:
> Hi,
>
> We're having problems with our PostgreSQL server using forever for simple
> queries, even when there's little load -- or rather, the transactions seem
> to take forever to commit. We're using 8.1 (yay!) on a single Opteron, with
> WAL on the system two-disk (software) RAID-1, separate from the database
> four-disk RAID-10. All drives are 10000rpm SCSI disks, with write cache
> turned off; we value our data :-) We're running Linux 2.6.13.4, with 64-bit
> kernel but 32-bit userspace.

You're beyond my area of expertise, but I do know that someone's going
to ask what filesystem this is (ext2/xfs/etc). And probably to see the
strace too.

Hmm - the only things I can think to check:
Do vmstat/iostat show any unusual activity?
Are your system logs on these disks too?
Could it be the journalling on the fs clashing with the WAL?

--
   Richard Huxton
   Archonet Ltd