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 i5AEPi015759 for ; Thu, 10 Jun 2004 10:25:44 -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 i5AEPfi5008859 for ; Thu, 10 Jun 2004 10:25:41 -0400 Received: from localhost (lucy.ukfsn.org [127.0.0.1]) by mail.ukfsn.org (Postfix) with ESMTP id 8F2A3E6A9E for ; Thu, 10 Jun 2004 15:23:31 +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 07517-19 for ; Thu, 10 Jun 2004 15:23:31 +0100 (BST) Received: from oak.dgreaves.com (modem-4077.karuhiruhi.dialup.pol.co.uk [81.78.143.237]) by mail.ukfsn.org (Postfix) with ESMTP id C2A34E6A8E for ; Thu, 10 Jun 2004 15:23:28 +0100 (BST) Received: from ash.dgreaves.com.dgreaves.com ([10.0.0.126]) by oak.dgreaves.com with esmtp (Exim 4.20) id 1BYQWJ-0007Sq-A5 for linux-lvm@redhat.com; Thu, 10 Jun 2004 15:27:07 +0100 Message-ID: <40C86F52.4090500@dgreaves.com> Date: Thu, 10 Jun 2004 15:25:22 +0100 From: David Greaves MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [linux-lvm] LVM2 seems to chop performance by 33% 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: linux-lvm@redhat.com Hi I didn't think lvm2 had such a big performance hit? 65Mb/s on the raid5 device 44Mb/s on the lv Is this expected? Kernel 2.6.6 representative dd's: cu:/huge/editing/tmp# time dd if=/dev/video_vg/video_lv of=/dev/null bs=1024k count=4k 4096+0 records in 4096+0 records out 4294967296 bytes transferred in 97.363340 seconds (44112777 bytes/sec) real 1m37.437s user 0m0.027s sys 0m27.126s yet: cu:/huge/editing/tmp# time dd if=/dev/md0 of=/dev/null bs=1024k count=4k 4096+0 records in 4096+0 records out 4294967296 bytes transferred in 65.715222 seconds (65357267 bytes/sec) real 1m5.770s user 0m0.026s sys 0m27.524s cu:/huge/editing/tmp# lvdisplay /dev/video_vg/video_lv --- Logical volume --- LV Name /dev/video_vg/video_lv VG Name video_vg LV UUID hyCwfR-d7ZG-lptP-XJFK-vMUb-JWE8-LgQSbb LV Write Access read/write LV Status available # open 2 LV Size 935.00 GB Current LE 14960 Segments 1 Allocation inherit Read ahead sectors 0 Block device 253:0 Changing Read ahead makes no difference (actually it slows it down a touch with values of 10 + 100) cu:/huge/editing/tmp# vgdisplay /dev/video_vg --- Volume group --- VG Name video_vg System ID Format lvm2 Metadata Areas 1 Metadata Sequence No 6 VG Access read/write VG Status resizable MAX LV 0 Cur LV 1 Open LV 1 Max PV 0 Cur PV 1 Act PV 1 VG Size 935.00 GB PE Size 64.00 MB Total PE 14960 Alloc PE / Size 14960 / 935.00 GB Free PE / Size 0 / 0 VG UUID kFVbcB-UgLa-XQjy-mF7R-BT2D-sUaA-uGUmeK cu:/huge/editing/tmp# pvdisplay /dev/md0 --- Physical volume --- PV Name /dev/md0 VG Name video_vg PV Size 935.00 GB / not usable 0 Allocatable yes (but full) PE Size (KByte) 65536 Total PE 14960 Free PE 0 Allocated PE 14960 PV UUID pEWAKP-tbaH-DSXP-W2jF-Pg6H-2z35-k1adQj David