Message-ID: <437B5859.9040805@commandprompt.com>
Date: Wed, 16 Nov 2005 08:03:37 -0800
From: "Joshua D. Drake" <jd@commandprompt.com>
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To: William Yu <wyu@talisys.com>
CC: pgsql-performance@postgresql.org
Subject: Re: Hardware/OS recommendations for large databases (
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>
> 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.

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.

>
> (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.

> Of course, this doesn't apply if you are an Intel/Dell-only shop. Xeon 
> DCs, while cheaper than their corresponding single-core SMPs, don't 
> have the same performance profile of Opteron DCs. Basically, you're 
> paying a bit extra so your server can generate a ton more heat.
>
Well if you are an Intel/Dell shop running PostgreSQL you have bigger 
problems ;)

Sincerely,

Joshua D. Drake


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