From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx3.redhat.com (mx3.redhat.com [172.16.48.32]) by int-mx1.corp.redhat.com (8.11.6/8.11.6) with ESMTP id i5EDP9025837 for ; Mon, 14 Jun 2004 09:25:09 -0400 Received: from mail.ukfsn.org (s2.ukfsn.org [217.158.120.143]) by mx3.redhat.com (8.12.10/8.12.10) with ESMTP id i5EDP3Xn012291 for ; Mon, 14 Jun 2004 09:25:04 -0400 Received: from localhost (lucy.ukfsn.org [127.0.0.1]) by mail.ukfsn.org (Postfix) with ESMTP id 62906E6A96 for ; Mon, 14 Jun 2004 14:24:58 +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 14491-19 for ; Mon, 14 Jun 2004 14:24:58 +0100 (BST) Received: from oak.dgreaves.com (modem-3547.kawau.dialup.pol.co.uk [81.78.157.219]) by mail.ukfsn.org (Postfix) with ESMTP id B9DCFE6A8E for ; Mon, 14 Jun 2004 14:24:57 +0100 (BST) Received: from ash.dgreaves.com ([10.0.0.121]) by oak.dgreaves.com with esmtp (Exim 4.20) id 1BZrUA-0005oS-4T for linux-lvm@redhat.com; Mon, 14 Jun 2004 14:26:50 +0100 Message-ID: <40CDA728.4080902@dgreaves.com> Date: Mon, 14 Jun 2004 14:24:56 +0100 From: David Greaves MIME-Version: 1.0 Subject: Re: [linux-lvm] LVM2 seems to chop performance by 33% References: <40C86F52.4090500@dgreaves.com> <40CD910A.9040605@ist.utl.pt> In-Reply-To: <40CD910A.9040605@ist.utl.pt> Content-Transfer-Encoding: quoted-printable 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="iso-8859-1"; format="flowed" To: LVM general discussion and development Miguel Cabe=EF=BF=BDa wrote: > Hi, > >> I didn't think lvm2 had such a big performance hit? >> >> 65Mb/s on the raid5 device >> 44Mb/s on the lv >> > Did you try to ajust the read ahead with blockdev on the LV itself? > > # blockdev --setra XXXX /dev/sda (raid5 device, just for comparisson) > # blockdev --setra XXXX /dev/vg/lv (lv) > > Try some values for the readahead. On my system I use 2048. No, I didn't hmm... man blockdev useful - new to me :) Not seen it on any googling to do with lvm. I'll try this later when it's idle - thanks for the suggestion. I do already have Read ahead sectors 100 in the lvdisplay yet blockdev --getra /dev/video_vg/video_lv reports 256 (and, to be sure --getss says 512byte sectors) Why is this different? David