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 (8.13.1/8.13.1) with ESMTP id l4P8fRYv025819 for ; Fri, 25 May 2007 04:41:27 -0400 Received: from relay2.gigamail.to (mail.tnp-online.de [212.80.247.147]) by mx1.redhat.com (8.13.1/8.13.1) with ESMTP id l4P8fOjk011693 for ; Fri, 25 May 2007 04:41:25 -0400 Received: from scanner5.gigamail.to (content5.cluster.gigamail.to [192.168.254.200]) by mxout2.gigamail.to (Postfix) with ESMTP id 34D81D2ABF for ; Fri, 25 May 2007 10:41:14 +0200 (CEST) Received: from chimp.subsystem.local (content5.cluster.gigamail.to [192.168.254.200]) by chimp.scanner5.gigamail.to (Postfix) with ESMTP id 02449EAB42 for ; Fri, 25 May 2007 10:41:14 +0200 (CEST) Received: from scanner5.gigamail.to (localhost [127.0.0.1]) by clamav-milter.scanner5.gigamail.to (Postfix) with ESMTP id 37806EAB61 for ; Fri, 25 May 2007 10:41:13 +0200 (CEST) Received: from relay1.gigamail.to (relay1.cluster.gigamail.to [192.168.254.12]) by scanner5.gigamail.to (Postfix) with ESMTP id 3230FEAB42 for ; Fri, 25 May 2007 10:41:13 +0200 (CEST) Received: from cheetah.dd.xiranet.com (162.237.80.212.static.versanetonline.de [212.80.237.162]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.ddkom-online.de (Postfix) with ESMTP id 80BD0108ACD for ; Fri, 25 May 2007 10:41:10 +0200 (CEST) Received: from [192.168.0.242] (dhcp242.dd.xiranet.com [192.168.0.242]) (authenticated bits=0) by cheetah.dd.xiranet.com (8.13.4/8.13.4/Debian-1) with ESMTP id l4P8emxV028880 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT) for ; Fri, 25 May 2007 10:40:52 +0200 Message-ID: <4656A10F.30000@web.de> Date: Fri, 25 May 2007 10:40:47 +0200 From: Mirko Benz MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [linux-lvm] LVM over MD performance 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 have a setup with 15 SATA drives configured as 3 x SW RAID with 5 drives each with 64k stripe size. Configuration: kernel version is 2.6.18-8.1.3.el5, CPU Xeon 5130, LSI PCI-X SAS controller. I am testing the devices in parallel with seq I/O using Oracle Orion and 1 MB block size. 3 x MD RAID 5 (all values in MB/s): Read: 800.42 Write: 564.75 When I setup a volume group + lv on each of the three devices I get the following results: Read: 729.28 (-9 %) Write: 362.30 (- 36 %) Is there a reason that write performance is so much slower? --- Striping: I would like to aggregate the individual RAID into a single vg with a lv using all disks. Using md with RAID 0 over 3 x RAID 5 I get the following results (stripe size is 256k): Read: 700.68 Write: 530.43 When using LVM to do the striping (-i 3 -I 256K) I get the following: Read: 660.71 (- 6%) Write: 149.29 (- 72%) Should one avoid LVM striping or are there some parameters that need to be adjusted? Regards, Mirko