Received: from magus.postgresql.org (magus.postgresql.org [87.238.57.229]) by mail.postgresql.org (Postfix) with ESMTP id 4650EC4CD76 for ; Thu, 3 May 2012 03:54:29 -0300 (ADT) Received: from out1.ip01ir2.opaltelecom.net ([62.24.128.237]) by magus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1SPpvo-0004aR-2C for pgsql-performance@postgresql.org; Thu, 03 May 2012 06:54:28 +0000 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: ApMBAGMrok9PS0JT/2dsb2JhbAANN7YzAQEBAQNJLwEQCxgJFg8JAwIBAgFFBg0BBwEBwwqLC4V9BKkpgVQ X-IronPort-AV: E=Sophos;i="4.75,522,1330905600"; d="scan'208,217";a="389856009" Received: from 79-75-66-83.dynamic.dsl.as9105.com (HELO [192.168.6.20]) ([79.75.66.83]) by out1.ip01ir2.opaltelecom.net with ESMTP; 03 May 2012 07:54:10 +0100 Message-ID: <4FA22B92.6050103@kickstone.co.uk> Date: Thu, 03 May 2012 07:54:10 +0100 From: John Lister Organization: Kickstone Technologies Ltd User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 MIME-Version: 1.0 To: Jan Nielsen CC: sthomas@peak6.com, pgsql-performance@postgresql.org Subject: Re: Configuration Recommendations References: <4F96FFE1.2030809@peak6.com> <4F97ABBB.1000708@kickstone.co.uk> <4F986CAC.4060904@peak6.com> In-Reply-To: Content-Type: multipart/alternative; boundary="------------030604080204070300000304" X-Pg-Spam-Score: -1.2 (-) X-Archive-Number: 201205/21 X-Sequence-Number: 46845 This is a multi-part message in MIME format. --------------030604080204070300000304 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit On 03/05/2012 03:10, Jan Nielsen wrote: > > 300GB RAID10 2x15k drive for OS on local storage > */dev/sda1 RA* 4096 > */dev/sda1 FS* ext4 > */dev/sda1 MO* > > 600GB RAID 10 8x15k drive for $PGDATA on SAN > *IO Scheduler sda* noop anticipatory deadline [cfq] > */dev/sdb1 RA* 4096 > */dev/sdb1 FS* xfs > */dev/sdb1 MO* allocsize=256m,attr2,logbufs=8,logbsize=256k,noatime > > 300GB RAID 10 2x15k drive for $PGDATA/pg_xlog on SAN > *IO Scheduler sdb* noop anticipatory deadline [cfq] > */dev/sde1 RA* 4096 > */dev/sde1 FS* xfs > */dev/sde1 MO* allocsize=256m,attr2,logbufs=8,logbsize=256k,noatime > * I was wondering if it would be better to put the xlog on the same disk as the OS? Apart from the occasional log writes I'd have thought most OS data is loaded into cache at the beginning, so you effectively have an unused disk. This gives you another spindle (mirrored) for your data. Or have I missed something fundamental? -- www.pricegoblin.co.uk --------------030604080204070300000304 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit On 03/05/2012 03:10, Jan Nielsen wrote:

300GB RAID10 2x15k drive for OS on local storage
*/dev/sda1 RA*                                            4096
*/dev/sda1 FS*                                            ext4 
*/dev/sda1 MO*

600GB RAID 10 8x15k drive for $PGDATA on SAN
*IO Scheduler sda*            noop anticipatory deadline [cfq]
*/dev/sdb1 RA*                                            4096
*/dev/sdb1 FS*                                             xfs
*/dev/sdb1 MO*        allocsize=256m,attr2,logbufs=8,logbsize=256k,noatime             

300GB RAID 10 2x15k drive for $PGDATA/pg_xlog on SAN
*IO Scheduler sdb*            noop anticipatory deadline [cfq]
*/dev/sde1 RA*                                            4096
*/dev/sde1 FS*                                             xfs
*/dev/sde1 MO*        allocsize=256m,attr2,logbufs=8,logbsize=256k,noatime
*

I was wondering if it would be better to put the xlog on the same disk as the OS? Apart from the occasional log writes I'd have thought most OS data is loaded into cache at the beginning, so you effectively have an unused disk. This gives you another spindle (mirrored) for your data.

Or have I missed something fundamental?

-- 
www.pricegoblin.co.uk
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