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Message-ID: <dcc563d10806170922m5983401ake7f70c9b88a9b9aa@mail.gmail.com>
Date: Tue, 17 Jun 2008 10:22:14 -0600
From: "Scott Marlowe" <scott.marlowe@gmail.com>
To: "Andrew Sullivan" <ajs@commandprompt.com>,
 pgsql-performance@postgresql.org
Subject: Re: Which hardware ?
In-Reply-To: <20080617154215.GI68434@commandprompt.com>
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On Tue, Jun 17, 2008 at 9:42 AM, Andrew Sullivan <ajs@commandprompt.com> wrote:
> On Tue, Jun 17, 2008 at 04:49:17PM +0200, Lionel wrote:
>> My tomcat webapp is well coded  and consumes nearly nothing.
>
> If I were ever inclined to say, "Nonsense," about code I've never
> seen, this is probably the occasion on which I'd do it.  A running JVM
> is necessarily going to use some memory, and that is memory use that
> you won't be able to factor out properly when developing models of
> your database system performance.

But if that amount of memory is 256 Megs and it only ever acts as a
control panel or data access point, it's probably not a huge issue.
If it's 2 Gig it's another issue.  It's all about scale.  The real
performance hog for me on all in one boxes has been perl / fastcgi
setups.

> The power of the system is hard to know about in the context (with
> only 8Go of memory, I don't consider this a powerful box at all,
> note).

I always think of main memory in terms of how high a cache hit rate it
can get me.  If 8G gets you a 50% hit rate, and 16G gets you a 95% hit
rate, then 16G is the way to go.  But if 8G gets you to 75% and 32G
gets you to 79% because of your usage patterns (the world isn't always
bell curve shaped) then 8G is plenty and it's time to work on faster
disk subsystems if you need more performance.