Received: from maia.hub.org (maia-3.hub.org [200.46.204.243]) by mail.postgresql.org (Postfix) with ESMTP id 80DC06322E8 for ; Wed, 28 Jul 2010 10:43:58 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.243]) (amavisd-maia, port 10024) with ESMTP id 53762-05 for ; Wed, 28 Jul 2010 13:43:49 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail-ey0-f174.google.com (mail-ey0-f174.google.com [209.85.215.174]) by mail.postgresql.org (Postfix) with ESMTP id E78A36318F3 for ; Wed, 28 Jul 2010 10:43:50 -0300 (ADT) Received: by eya25 with SMTP id 25so1011905eya.19 for ; Wed, 28 Jul 2010 06:43:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from :user-agent:mime-version:to:subject:references:in-reply-to :content-type:content-transfer-encoding; bh=iHWFQgHyL3jTRO8ZjZ/KzDJyTypUUNr/iffPGguFTKg=; b=frUpM8SnNkK3rG/+MSRfGJjF32zAx7/49OSQKS4DY0P11hUoD1HjEQlPAJI5VGfdJL fvTzwiKd16P0/rsNSLt8GZINsT++1Rck7owysbPrjUWJ3wpWVyAoBJQUcgxe3G8nTpsT ynqK61dsskS6gv5/esFnYWf/F2spUVcta92g8= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:user-agent:mime-version:to:subject:references :in-reply-to:content-type:content-transfer-encoding; b=EndAwD+gjqkR4wg0BFdMoTtpnMblWJnJlDx+oOg4sjFPhRMwjPuL8zCXgxIgwUqXdb d/zXlAw61m4yKwntc+R/xYN7uPcmujBN9oggSmKaZzoB8zJ9N+psKUD2XbquxF3BbW+s IfwE9EffYy2VZozUm432KMEbZ9W9ZZE4XjB4s= Received: by 10.213.14.208 with SMTP id h16mr5893007eba.7.1280324628643; Wed, 28 Jul 2010 06:43:48 -0700 (PDT) Received: from [0.0.0.0] (5357DA75.cable.casema.nl [83.87.218.117]) by mx.google.com with ESMTPS id a48sm9530627eei.18.2010.07.28.06.43.47 (version=TLSv1/SSLv3 cipher=RC4-MD5); Wed, 28 Jul 2010 06:43:47 -0700 (PDT) Message-ID: <4C503473.5080105@gmail.com> Date: Wed, 28 Jul 2010 15:45:23 +0200 From: Yeb Havinga User-Agent: Thunderbird 2.0.0.24 (Windows/20100228) MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Re: Testing Sandforce SSD References: <4C4A9452.9070100@gmail.com> <4C4B1F84.5030306@2ndquadrant.com> <4C4C83DF.3010703@gmail.com> <4C4C8CCC.7080406@gmail.com> <4C4D6396.5020707@gmail.com> <4C4DAAE8.3060501@2ndquadrant.com> <4C4DE50B.1060102@gmail.com> <4C4DE5C9.8090004@2ndquadrant.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit 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 X-Spam-Level: X-Archive-Number: 201007/434 X-Sequence-Number: 39823 Michael Stone wrote: > On Mon, Jul 26, 2010 at 03:23:20PM -0600, Greg Spiegelberg wrote: >> I know I'm talking development now but is there a case for a pg_xlog >> block >> device to remove the file system overhead and guaranteeing your data is >> written sequentially every time? > > If you dedicate a partition to xlog, you already get that in practice > with no extra devlopment. Due to the LBA remapping of the SSD, I'm not sure of putting files that are sequentially written in a different partition (together with e.g. tables) would make a difference: in the end the SSD will have a set new blocks in it's buffer and somehow arrange them into sets of 128KB of 256KB writes for the flash chips. See also http://www.anandtech.com/show/2899/2 But I ran out of ideas to test, so I'm going to test it anyway. regards, Yeb Havinga