Re: effective_cache_size less than shared_buffers

On Wed, 2009-02-25 at 17:04 -0800, Josh Berkus wrote:
> Joshua D. Drake wrote:
> > On Wed, 2009-02-25 at 17:21 -0600, Kevin Grittner wrote:
> >> Should we log a warning at startup when effective_cache_size is less
> >> than shared_buffers?
> >
> > I would say no. Although I could see an argument for the default
> > effective_cache_size always being the same size as shared_buffers.
>
> That's certainly not what we've meant historically by ECS. Generally
> it's been the size of shared_buffers *and* the FS cache. If it were
> just the size of shared_buffers, then we wouldn't need a 2nd setting,
> would we?

We can't determine the size of the FS cache. We can determine the size
of the shared_buffers. The idea here is to eliminate one of those by
default PostgreSQL is slow issues. Since we are already using X amount
of shared_buffers we know we have at least X amount of cache.

Sincerely,

Joshua D. Drake

>
> --Josh
>
>
--
PostgreSQL - XMPP: jdrake(at)jabber(dot)postgresql(dot)org
Consulting, Development, Support, Training
503-667-4564 - http://www.commandprompt.com/
The PostgreSQL Company, serving since 1997