From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (mx1.redhat.com [172.16.48.31]) by int-mx1.corp.redhat.com (8.11.6/8.11.6) with ESMTP id i5KII9022429 for ; Sun, 20 Jun 2004 14:18:09 -0400 Received: from mail.ukfsn.org (s2.ukfsn.org [217.158.120.143]) by mx1.redhat.com (8.12.10/8.12.10) with ESMTP id i5KII8e1018437 for ; Sun, 20 Jun 2004 14:18:08 -0400 Received: from localhost (lucy.ukfsn.org [127.0.0.1]) by mail.ukfsn.org (Postfix) with ESMTP id 45D09E6D46 for ; Sun, 20 Jun 2004 19:17:24 +0100 (BST) Received: from mail.ukfsn.org ([127.0.0.1]) by localhost (lucy.ukfsn.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 23107-06 for ; Sun, 20 Jun 2004 19:17:24 +0100 (BST) Received: from oak.dgreaves.com (modem-2288.karuhiruhi.dialup.pol.co.uk [81.78.136.240]) by mail.ukfsn.org (Postfix) with ESMTP id 74215E6D3B for ; Sun, 20 Jun 2004 19:17:23 +0100 (BST) Received: from ash.dgreaves.com ([10.0.0.66]) by oak.dgreaves.com with esmtp (Exim 4.20) id 1Bc6vG-0000bc-9w for linux-lvm@redhat.com; Sun, 20 Jun 2004 19:20:06 +0100 Message-ID: <40D5D4D6.9020307@dgreaves.com> Date: Sun, 20 Jun 2004 19:17:58 +0100 From: David Greaves MIME-Version: 1.0 Subject: Re: [linux-lvm] LVM2 seems to chop performance by 33% References: <40C86F52.4090500@dgreaves.com> <200406101105.47606.StuartHarper@tampabay.rr.com> <40C87F8A.7080304@dgreaves.com> <1086885029.13087.15.camel@localhost> In-Reply-To: <1086885029.13087.15.camel@localhost> Content-Transfer-Encoding: 7bit Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: LVM general discussion and development Clint Byrum wrote: >On Thu, 2004-06-10 at 08:34, David Greaves wrote: > > >>Thanks >> >>I'd tried that, but no real change. I started 1t 128k and also tried >>64k, 256k :) (oh, and 1k) >> >> >> > >I did some tests a few months ago with bonnie++.. might offer some >encouragement (please don't post this to slashdot.. ;) > >http://spamaps.org/raidtests.php > >There's a lot of data there, but if you look at the LVM stuff, you might >notice that the concurrent performance (having 3 processes hammering the >disks in different places instead of just one) was quite good when >compared to flat out RAID5. I'll pay 5% performance for manageability >any day. :-D > > Thanks to those that made suggestions. In the end I used blockdev --setra 4096 on all my devices (/dev/sda,b,c,d and the /dev/md0 and the /dev/video_vg/video_lv) and this doubled throughput. I am reading multi-gigabyte video files so these parameters are not for everyone. No-one ever replied as to why blockdev --setra / --getra is not the same as that displayed in lvdisplay And it's not documented that I can find. There's a comment: "Not used by device-mapper." And that means.....? It's ignored? not implemented yet? Good luck? # lvdisplay /dev/video_vg/huge_lv --- Logical volume --- LV Name /dev/video_vg/huge_lv VG Name video_vg LV UUID 3kz7n9-97Rg-2LJw-J9ml-1BBS-jGs0-Onh4NI LV Write Access read/write LV Status available # open 1 LV Size 312.50 GB Current LE 5000 Segments 1 Allocation inherit Read ahead sectors 120 Block device 253:1 # blockdev --getra /dev/video_vg/huge_lv 4096 Let this post be there for Google - the modern man-page for linux. (if you've got your fingers crossed!) David