Received: from maia.hub.org (maia-5.hub.org [200.46.204.29])
	by mail.postgresql.org (Postfix) with ESMTP id 6A7D41337B4E
	for <pgsql-performance-postgresql.org@mail.postgresql.org>;
	Sat,  5 Feb 2011 04:50:21 -0400 (AST)
Received: from mail.postgresql.org ([200.46.204.86])
	by maia.hub.org (mx1.hub.org [200.46.204.29]) (amavisd-maia, port 10024)
	with ESMTP id 06573-10
	for <pgsql-performance-postgresql.org@mail.postgresql.org>;
	Sat,  5 Feb 2011 08:50:15 +0000 (UTC)
X-Greylist: from auto-whitelisted by SQLgrey-1.7.6
Received: from moutng.kundenserver.de (moutng.kundenserver.de
	[212.227.126.171])
	by mail.postgresql.org (Postfix) with ESMTP id E4BC41337B84
	for <pgsql-performance@postgresql.org>;
	Sat,  5 Feb 2011 04:50:13 -0400 (AST)
Received: from [192.168.1.6] (mail.highperformancepostgresql.com
	[71.179.240.8])
	by mrelayeu.kundenserver.de (node=mreu2) with ESMTP (Nemesis)
	id 0MH3DS-1PzRLj0ZVa-00EHGw; Sat, 05 Feb 2011 09:49:10 +0100
Message-ID: <4D4D0F01.6070407@2ndquadrant.com>
Date: Sat, 05 Feb 2011 03:49:05 -0500
From: Greg Smith <greg@2ndquadrant.com>
User-Agent: Thunderbird 2.0.0.24 (X11/20100317)
MIME-Version: 1.0
To: Scott Marlowe <scott.marlowe@gmail.com>
CC: Robert Haas <robertmhaas@gmail.com>, david@lang.hm,
	Vitalii Tymchyshyn <tivv00@gmail.com>,
	Kenneth Marshall <ktm@rice.edu>, Jon Nelson <jnelson+pgsql@jamponi.net>,
	Andrew Dunstan <andrew@dunslane.net>,
	Bruce Momjian <bruce@momjian.us>, Tom Lane <tgl@sss.pgh.pa.us>,
	Craig Ringer <craig@postnewspapers.com.au>,
	"pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: [HACKERS] Slow count(*) again...
References: <AANLkTiknZi97dDwm7sHqy0EL7tpNEP9sY5uPV6AN+q=u@mail.gmail.com>
	<4D499E55.4020107@vmsinfo.com>
	<AANLkTimo2J-BagObs_V1bGaHOO9qL+kTF6s6-wZ=M3KW@mail.gmail.com>
	<AANLkTin7A_Q=Yc9Wf_5=POp2mVqmaiwqUDsFMLG68H45@mail.gmail.com>
	<4D4A7B69.2020704@gmail.com>
	<alpine.DEB.2.00.1102030208440.8162@asgard.lang.hm>
	<AANLkTi=Thet0VZ-X6b7tek+iSLVkE27JjiKrB5D8U0Jd@mail.gmail.com>
	<alpine.DEB.2.00.1102031243190.10088@asgard.lang.hm>
	<AANLkTikmChsPODbUD4V-gQ8k2yYvvjJY6b9K_29+k7nu@mail.gmail.com>
	<alpine.DEB.2.00.1102031637480.30983@asgard.lang.hm>
	<20110204143315.GA1261@aart.is.rice.edu>	<4D4C0F66.1080507@gmail.com>
	<alpine.DEB.2.00.1102042142571.8162@asgard.lang.hm>
	<AANLkTi=EkCUkQs9VTtW4aOBNNNV0gi8jYZhNgdHuFTKM@mail.gmail.com>
	<AANLkTikKTc2GPm87Liztk3UTdRY+_THquaaW3qoMe2+d@mail.gmail.com>
In-Reply-To: <AANLkTikKTc2GPm87Liztk3UTdRY+_THquaaW3qoMe2+d@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-Provags-ID: V02:K0:fvUI39ldgwvdPiDEaoYORMNzgcczfRBMRDze3DNqmj2
	OS2/UTWxJL3YKDDQPcenmiRHYJsX2g3Cz8Ka4AtAq8UGICR+fc
	JBuT3mCOurJ9IMB6UBEZsbAFXw+TvqymgG/4qsHc7knPXKzyUE
	Rrp81g5BbVpKoSBbrEsxX6w23qc3v2kWBixcZNTgkUZLnjFFd2
	qLHpFO3efqsWJEyJMI7yzIlDYaFuuWcU7nWysUn9Bs=
X-Virus-Scanned: Maia Mailguard 1.0.1
X-Spam-Status: No, hits=-1.9 tagged_above=-10 required=5 tests=BAYES_00=-1.9,
	RCVD_IN_DNSWL_NONE=-0.0001
X-Spam-Level: 
X-Archive-Number: 201102/243
X-Sequence-Number: 42381

Scott Marlowe wrote:
> With a 24 drive RAID-10 array that can read at ~1GB/s I am almost
> always CPU bound during copies.  This isn't wholly bad as it leaves
> spare IO for the rest of the machine so regular work carries on just
> fine.
>   

And you don't need nearly that much I/O bandwidth to reach that point.  
I've hit being CPU bound on COPY...FROM on systems with far less drives 
than 24.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support  www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books