Re: Hardware/OS recommendations for large databases (

On 11/16/05, Joshua D. Drake <jd(at)commandprompt(dot)com> wrote:
> >
> > The only questions would be:
> > (1) Do you need a SMP server at all? I'd claim yes -- you always need
> > 2+ cores whether it's DC or 2P to avoid IO interrupts blocking other
> > processes from running.
>
> I would back this up. Even for smaller installations (single raid 1, 1
> gig of ram). Why? Well because many applications are going to be CPU
> bound. For example
> we have a PHP application that is a CMS. On a single CPU machine, RAID 1
> it takes about 300ms to deliver a single page, point to point. We are
> not IO bound.
> So what happens is that under reasonable load we are actually waiting
> for the CPU to process the code.
>

This is the performance profile for PHP, not for Postgresql. This is
the postgresql mailing list.

> A simple upgrade to an SMP machine literally doubles our performance
> because we are still not IO bound. I strongly suggest that everyone use
> at least a single dual core because of this experience.
>

Performance of PHP, not postgresql.

> >
> > (3) Do you need an insane amount of memory? Well here's the case where
> > the more expensive motherboard will serve you better since each CPU
> > slot has its own bank of memory. Spend more money on memory, get
> > cheaper single-core CPUs.
> Agreed. A lot of times the slowest dual-core is 5x what you actually
> need. So get the slowest, and bulk up on memory. If nothing else memory
> is cheap today and it might not be tomorrow.
[snip]

Running postgresql on a single drive RAID 1 with PHP on the same
machine is not a typical installation.

300ms for PHP in CPU time? wow dude - that's quite a page. PHP
typical can handle up to 30-50 pages per second for a typical OLTP
application on a single CPU box. Something is really wrong with that
system if it takes 300ms per page.

Alex.