Re: [Testperf-general] Re: ExclusiveLock

Simon Riggs wrote:
> On Mon, 2004-11-22 at 23:37, Greg Stark wrote:
> > Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> >
> > > - Find a way to reduce rotational delay when repeatedly writing last WAL
> > > page
> > >
> > > Currently fsync of WAL requires the disk platter to perform a full
> > > rotation to fsync again. One idea is to write the WAL to different
> > > offsets that might reduce the rotational delay.
> >
> > Once upon a time when you formatted hard drives you actually gave them an
> > interleave factor for a similar reason. These days you invariably use an
> > interleave of 1, ie, store the blocks continuously. Whether that's because
> > controllers have become fast enough to keep up with the burst rate or because
> > the firmware is smart enough to handle the block interleaving invisibly isn't
> > clear to me.
> >
> > I wonder if formatting the drive to have an interleave >1 would actually
> > improve performance of the WAL log.
> >
> > It would depend a lot on the usage pattern though. A heavily used system might
> > be able to generate enough WAL traffic to keep up with the burst rate of the
> > drive. And an less used system might benefit but might lose.
> >
> > Probably now the less than saturated system gets close to the average
> > half-rotation-time latency. This idea would only really help if you have a
> > system that happens to be triggering pessimal results worse than that due to
> > unfortunate timing.
>
> I was asking whether that topic should be removed, since Tom had said it
> had been rejected....

The method used to fix it was rejected, but the goal of making it better
is still a valid one.

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