Received: from localhost (unknown [200.46.204.184]) by postgresql.org (Postfix) with ESMTP id 8E0BA9F9CB1 for ; Tue, 11 Sep 2007 20:02:55 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.184]) (amavisd-maia, port 10024) with ESMTP id 63539-04 for ; Tue, 11 Sep 2007 20:02:44 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.5 Received: from oxford.xeocode.com (unknown [87.127.95.196]) by postgresql.org (Postfix) with ESMTP id 6B7C49F9C6B for ; Tue, 11 Sep 2007 20:02:50 -0300 (ADT) Received: from localhost.enta.net ([127.0.0.1] helo=oxford.xeocode.com) by oxford.xeocode.com with esmtp (Exim 4.67) (envelope-from ) id 1IVEko-0001HV-KL; Wed, 12 Sep 2007 00:02:46 +0100 To: "Decibel!" Cc: "Jean-David Beyer" , Subject: Re: random_page_costs - are defaults of 4.0 realistic for SCSI RAID 1 In-Reply-To: <20070911213105.GF38801@decibel.org> (Decibel!'s message of "Tue\, 11 Sep 2007 16\:31\:05 -0500") User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.1 (gnu/linux) X-Draft-From: ("nnimap+mail01.enterprisedb.com:INBOX.performance" 2407) References: <87lkbdlkxw.fsf@oxford.xeocode.com> <46E676D6.70807@verizon.net> <87zlzt9ifw.fsf@oxford.xeocode.com> <46E6E338.5050403@verizon.net> <20070911213105.GF38801@decibel.org> From: Gregory Stark Organization: EnterpriseDB Date: Wed, 12 Sep 2007 00:02:46 +0100 Message-ID: <87r6l4ajqh.fsf@oxford.xeocode.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200709/207 X-Sequence-Number: 26752 "Decibel!" writes: > On Tue, Sep 11, 2007 at 02:49:28PM -0400, Jean-David Beyer wrote: >> It is tricky for me to find a big enough file to test. I tried one of the > > dd if=/dev/zero of=bigfile bs=8192 count=1000000 On linux another useful trick is: echo 1 > /proc/sys/vm/drop_caches Also, it helps to run a "vmstat 1" in another window and watch the bi and bo columns. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com