On 16/01/2004, at 2:44 AM, Tom Lane wrote:
...
> As noted elsewhere, it's highly likely that this has nothing to do with
> the OS, and everything to do with write caching in the disks being
> used.
>
> I assume you are benchmarking small individual transactions (one insert
> per xact). In such scenarios it's essentially impossible to commit
> more
> than one transaction per revolution of the WAL disk, because you have
> to
> write the same WAL disk page repeatedly and wait for it to get down to
> the platter. When you get results that are markedly in excess of the
> disk RPM figure, it's proof positive that the disk is lying about write
> complete (or that you don't have fsync on).
>
Tom, thanks for this explanation - we'll check this out straight away,
but it would explain a lot.