X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org
Received: from localhost (av.hub.org [200.46.204.144])
	by svr1.postgresql.org (Postfix) with ESMTP id 50540D9E93
	for <pgsql-performance-postgresql.org@localhost.postgresql.org>;
	Mon, 21 Nov 2005 10:57:08 -0400 (AST)
Received: from svr1.postgresql.org ([200.46.204.71])
	by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024)
	with ESMTP id 33574-01
	for <pgsql-performance-postgresql.org@localhost.postgresql.org>;
	Mon, 21 Nov 2005 14:57:11 +0000 (GMT)
X-Greylist: from auto-whitelisted by SQLgrey-
Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130])
	by svr1.postgresql.org (Postfix) with ESMTP id 6B417D9BAB
	for <pgsql-performance@postgresql.org>;
	Mon, 21 Nov 2005 10:57:05 -0400 (AST)
Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1])
	by sss.pgh.pa.us (8.13.1/8.13.1) with ESMTP id jALEuk8u001612;
	Mon, 21 Nov 2005 09:56:46 -0500 (EST)
To: "Luke Lonergan" <llonergan@greenplum.com>
cc: "Alan Stange" <stange@rentec.com>, "Greg Stark" <gsstark@mit.edu>,
	"Dave Cramer" <pg@fastcrypt.com>, "Joshua Marsh" <icub3d@gmail.com>,
	pgsql-performance@postgresql.org
Subject: Re: Hardware/OS recommendations for large databases ( 
In-reply-to: <BFA6C187.1425C%llonergan@greenplum.com> 
References: <BFA6C187.1425C%llonergan@greenplum.com>
Comments: In-reply-to "Luke Lonergan" <llonergan@greenplum.com>
	message dated "Mon, 21 Nov 2005 00:12:55 -0800"
Date: Mon, 21 Nov 2005 09:56:46 -0500
Message-ID: <1611.1132585006@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
X-Virus-Scanned: by amavisd-new at hub.org
X-Spam-Status: No, score=0.004 required=5 tests=[AWL=0.004]
X-Spam-Score: 0.004
X-Spam-Level: 
X-Archive-Number: 200511/419
X-Sequence-Number: 15676

"Luke Lonergan" <llonergan@greenplum.com> writes:
> OK - slower this time:

> We've seen between 110MB/s and 120MB/s on a wide variety of fast CPU
> machines with fast I/O subsystems that can sustain 250MB/s+ using dd, but
> which all are capped at 120MB/s when doing sequential scans with different
> versions of Postgres.

Luke, sometime it would be nice if you would post your raw evidence
and let other people do their own analysis.  I for one have gotten
tired of reading sweeping generalizations unbacked by any data.

I find the notion of a magic 120MB/s barrier, independent of either
CPU or disk speed, to be pretty dubious to say the least.  I would
like to know exactly what the "wide variety" of data points you
haven't shown us are.

			regards, tom lane