Re: shared_buffers documentation

On Mon, Apr 19, 2010 at 10:21 AM, Kevin Grittner
<Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
>> 2. Reading the section on checkpoint_segments reminds me, again,
>> that the current value seems extremely conservative on modern
>> hardware.  It's quite easy to hit this when doing large bulk data
>> loads or even a big ol' CTAS.  I think we should consider raising
>> this for 9.1.
>
> Perhaps, but be aware the current default benchmarked better
> than a larger setting in bulk loads.
>
> http://archives.postgresql.org/pgsql-hackers/2009-06/msg01382.php
>
> The apparent reason is that when there were fewer of them the WAL
> files were re-used before the RAID controller flushed them from BBU
> cache, causing an overall reduction in disk writes.  I have little
> doubt that *without* a good BBU cached controller a larger setting
> is better, but it's not universally true that bigger is better on
> this one.

I don't actually know what's best. I'm just concerned that we have a
default in postgresql.conf and a tuning guide that says "don't do
that". Maybe the tuning guide needs to be more nuanced, or maybe
postgresql.conf needs to be changed, but it makes no sense to have
them saying contradictory things.

...Robert