From mboxrd@z Thu Jan 1 00:00:00 1970 From: Terrence Martin Subject: Write Performance double Read Performance Date: Mon, 22 Mar 2004 11:32:06 -0800 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <405F3F36.6020109@physics.ucsd.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from newport.ucsd.edu ([132.239.73.89]:37855 "EHLO localhost.localdomain") by vger.kernel.org with ESMTP id S262316AbUCVTcG (ORCPT ); Mon, 22 Mar 2004 14:32:06 -0500 Received: from physics.ucsd.edu (newport [127.0.0.1]) by localhost.localdomain (8.12.10/8.12.10) with ESMTP id i2MJW6LH030827 for ; Mon, 22 Mar 2004 11:32:06 -0800 List-Id: linux-scsi@vger.kernel.org To: linux-scsi@vger.kernel.org I have the following system(s) Dual 2.8 Ghz Xeon 2U Supermicro Server with 2GB RAM Qlogic QLA2310f Controller attached to an... Infortrend A16F with 16 300GB WD IDE PATA Drives The array as a RAID 5 Array with 3 partitions of 1.4TB each. I have mounted one of the partitions to test. The OS is.... Fedora Core 1 with the latest Fedora 2.4 Kernel (2.4.22-1.2174.nptlsmp) I have compiled the QLA drivers from the Qlogic site and am using v6.06.10. The problem I am noticing is that while doing an IOZone performance test I get nice write performance when the test gets to large files. However my read performance seems to be a little over half my write. I thought the read should always be faster than the write? Command line used: /opt/iozone/bin/iozone -Ra -g 4G -i 0 -i 1 Eg. Copy paste from IOZone run KB reclen write rewrite read reread 2097152 64 154313 171266 91012 92388 2097152 128 154125 170701 89532 82991 2097152 256 151473 169734 86227 85231 2097152 512 150925 168767 84953 86313 2097152 1024 154947 175371 84576 85733 2097152 2048 154581 175161 84865 85233 2097152 4096 155754 175689 85229 86450 2097152 8192 155847 175645 85320 86052 2097152 16384 155500 175313 84817 86864 I only notice this performance drop once I get into large reads. Here when the file is half RAM performance is very good. KB reclen write rewrite read reread 1048576 64 174326 236646 1571371 1722042 1048576 128 171660 236849 1552772 1699937 1048576 256 173722 239855 893958 938153 1048576 512 171075 238875 660975 683853 1048576 1024 169105 239178 651627 675901 1048576 2048 167846 240387 649875 673732 1048576 4096 168663 238126 653533 675654 1048576 8192 171406 239028 646698 669387 1048576 16384 171545 237270 647777 669695 Before I went down the road of compiling various kernels etc I thought I would post this to linux-scsi to see if it is just some configuration setting to a driver or kernel parameter that needs to be tweaked. Of course I could be completely reading this wrong but bonnie++ also appears to give similar results and vmstat is similarly low on the read side. Thanks, Terrence