Re: Maximum transaction rate

Jack Orenstein <jack(dot)orenstein(at)hds(dot)com> writes:
> The transaction rates I'm getting seem way too high: 2800-2900 with
> one thread, 5000-7000 with ten threads. I'm guessing that writes
> aren't really reaching the disk. Can someone suggest how to figure out
> where, below postgres, someone is lying about writes reaching the
> disk?

AFAIK there are two trouble sources in recent Linux machines: LVM and
the disk drive itself. LVM is apparently broken by design --- it simply
fails to pass fsync requests. If you're using it you have to stop.
(Which sucks, because it's exactly the kind of thing DBAs tend to want.)
Otherwise you need to reconfigure your drive to not cache writes.
I forget the incantation for that but it's in the PG list archives.

regards, tom lane