Subject: Re: Question on pgbench output
From: Simon Riggs <simon@2ndQuadrant.com>
To: David Kerr <dmk@mr-paradox.net>
Cc: pgsql-performance@postgresql.org
In-Reply-To: <20090403233458.GC54342@mr-paradox.net>
References: <20090403195302.GA54342@mr-paradox.net>
	<alpine.GSO.2.01.0904031721570.5502@westnet.com>
	<24809.1238799146@sss.pgh.pa.us>
	<20090403233458.GC54342@mr-paradox.net>
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Date: Sun, 05 Apr 2009 08:01:39 +0100
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On Fri, 2009-04-03 at 16:34 -0700, David Kerr wrote:
> 400 concurrent users doesn't mean that they're pulling 1.5 megs /
> second every second. Just that they could potentially pull 1.5 megs at
> any one second. most likely there is a 6 (minimum) to 45 second
> (average) gap  between each individual user's pull.

There's a world of difference between 400 connected and 400 concurrent
users. You've been testing 400 concurrent users, yet without measuring
data transfer. The think time will bring the number of users right down
again, but you really need to include the much higher than normal data
transfer into your measurements and pgbench won't help there.

-- 
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support