From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264071AbUDBPWB (ORCPT ); Fri, 2 Apr 2004 10:22:01 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264074AbUDBPWA (ORCPT ); Fri, 2 Apr 2004 10:22:00 -0500 Received: from kinesis.swishmail.com ([209.10.110.86]:48132 "EHLO kinesis.swishmail.com") by vger.kernel.org with ESMTP id S264071AbUDBPV6 (ORCPT ); Fri, 2 Apr 2004 10:21:58 -0500 Message-ID: <406D89B8.4090308@techsource.com> Date: Fri, 02 Apr 2004 10:41:44 -0500 From: Timothy Miller MIME-Version: 1.0 To: Linux Kernel Mailing List Subject: PROBLEM: Consistently slower 3ware RAID performance under 2.6.4 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org ## Background: I'm doing a lot of sequential read and write performance tests on my 3ware 7000-2 controller (RAID1 with 2xWD1200JB), because I'm getting very poor write performance. This is a problem that I'm currently working with 3ware to resolve, and they are working enthusiastically with me to fix it. Read test: time dd if=/dev/sda2 of=/dev/null bs=1024k count=1024 Write test: time dd if=/dev/zero of=/dev/sda2 bs=1024k count=1024 NOTE: /dev/sda2 is the swap partition which is NEAR the outer-most tracks. ## The new problem I discovered specific to Linux: Regardless of the above-mentioned problem, I am noticing a very significant performance drop between a 2.4 kernel and a 2.6 kernel. ## Performance with "2.4.25-gentoo": The read test here takes 21.6 seconds which is about 47MB/sec. This is a correct number, because I have measured the maximum read throughput from each drive to be 47MB/sec. The write test here takes 2 minutes, 2.5 seconds. This translates to 8.35MB/sec. This is what I'm working with 3ware to correct, but let's call this the baseline write performance. ## Performance with "2.6.4-gentoo-r1": The read test here takes 33.9 seconds. That's down to about 30MB/sec. The write test here takes 2 minutes, 44.2 seconds. That is down to 6.2MB/sec. ## HELP? How can I help kernel developers to diagnose this problem? What information do I need to provide that is missing? What is responsible for such a significant performance drop on LONG sequential disk accesses? ## My computer: Athlon 2800+ 1GB RAM (Corsair 2700LL) ABIT KD7 (KT400 chipset) Thanks in advance for the help!