Received: from magus.postgresql.org (magus.postgresql.org [87.238.57.229]) by mail.postgresql.org (Postfix) with ESMTP id 54E20171224E for ; Tue, 6 Mar 2012 20:37:23 -0400 (AST) Received: from [2404:130:0:10::40:2] (helo=mail.catalyst.net.nz) by magus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1S54sa-0001hH-Tr for pgsql-performance@postgresql.org; Wed, 07 Mar 2012 00:37:22 +0000 Received: from localhost (localhost [127.0.0.1]) by mail.catalyst.net.nz (Postfix) with ESMTP id A22FB31D3C; Wed, 7 Mar 2012 13:37:02 +1300 (NZDT) X-Virus-Scanned: Debian amavisd-new at catalyst.net.nz Received: from mail.catalyst.net.nz ([127.0.0.1]) by localhost (bertrand.catalyst.net.nz [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id vNBcZkwCXL8x; Wed, 7 Mar 2012 13:37:00 +1300 (NZDT) Received: from [IPv6:2404:130:0:1000:222:15ff:fe5c:2471] (unknown [IPv6:2404:130:0:1000:222:15ff:fe5c:2471]) (Authenticated sender: mark.kirkwood) by mail.catalyst.net.nz (Postfix) with ESMTPSA id 9FBDC31D36; Wed, 7 Mar 2012 13:37:00 +1300 (NZDT) Message-ID: <4F56ADA5.4040902@catalyst.net.nz> Date: Wed, 07 Mar 2012 13:36:53 +1300 From: Mark Kirkwood User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.2) Gecko/20120216 Thunderbird/10.0.2 MIME-Version: 1.0 To: Yeb Havinga CC: pgsql-performance@postgresql.org Subject: Re: SSD and RAID References: <4F554025.9040101@catalyst.net.nz> <4F55C802.8040401@gmail.com> In-Reply-To: <4F55C802.8040401@gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Host-Lookup-Failed: Reverse DNS lookup failed for 2404:130:0:10::40:2 (failed) X-Pg-Spam-Score: -1.1 (-) X-Archive-Number: 201203/70 X-Sequence-Number: 46520 On 06/03/12 21:17, Yeb Havinga wrote: > > > One thing to note is that linux software raid with md doesn't support > discard, which might shorten the drive's expected lifetime. To get > some numbers I tested the raid 1 of ssd's setup for mediawear under a > PostgreSQL load earlier, see > http://archives.postgresql.org/pgsql-general/2011-11/msg00141.php > > Right, which is a bit of a pain - we are considering either formatting the drive with less capacity and using md RAID 1 or else doing the mirror in LVM to enable a working discard/trim. Regards Mark