Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 29 Nov 2001 16:37:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 29 Nov 2001 16:36:56 -0500 Received: from mail.myrio.com ([63.109.146.2]:22004 "HELO smtp1.myrio.com") by vger.kernel.org with SMTP id convert rfc822-to-8bit; Thu, 29 Nov 2001 16:36:45 -0500 Message-ID: From: Torrey Hoffman To: "'Rene Rebe'" , linux-kernel@vger.kernel.org Cc: reiserfs-list@namesys.com Subject: RE: [reiserfs-list] ReiserFS on RAID5 Linux-2.4 - speed problem Date: Thu, 29 Nov 2001 13:36:08 -0800 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2650.21) Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Ren? Rebe wrote: [...] > I run ReiserFS on a RAID5 (of 3 IDE disks) using the latest > 2.4.(e.g.16) > kernel for weeks. It works well except that is is painfully > slow. [...] You are not the only one with these problems... I am convinced there is a serious, negative performance interaction between software RAID 5 and ReiserFS, at least on IDE. Performance is less than 25% of what it should be. --------------- Concise summary: dbench of reiserfs on a normal drive partition is slightly * faster * than timing a raw "dd" from that partition. But, dbench of reiserfs on a reiserfs on software RAID5 is ** only 1/4 as fast ** as a raw "dd" from the RAID5, And, to make it worse, software RAID 5 is significantly slower than I think it should be. As a result, my nice RAID 5 is far, far slower than an ordinary partition. These are not just dbench numbers - all sorts of testing shows the problem. --------------- Here are the details: I have four Maxtor 60 GB IDE disks, each is master on a single cable, using two Promise Ultra TX2/100 cards. The host is a dual P3-800 with 512 MB of RAM. I bought this hardware specifically to act as a fast, cheap, reliable server... I have no complaints except the speed. The raid disks are hde, hdg, hdi, hdk, as /dev/md0, not partitioned, /dev/md0 is a single 180 GB reiserfs and is mounted on /home. Chunk size is 1024. Here's some low level numbers: Single drive from the RAID: time dd if=/dev/hdg of=/dev/null bs=1M count=1024 - elapsed time 0:37 = 27.65 MB/sec Raw RAID5: time dd if=/dev/md0 of=/dev/null bs=1M count=1024 - elapsed time 0:25 = 40.96 MB/sec File on Reiserfs on RAID5: time dd if=/home/test_file_1GB of=/dev/null bs=1M count=1024 - elapsed time 0:33 = 31.03 MB/sec Old home partition on hda9: time dd if=/dev/hda9 of=/dev/null bs=1M count=1024 - elapsed time 0:41 = 24 MB/sec dbench tests: dbench 32 on reiserfs on md0 : 10.7027 MB/sec dbench 32 on reiserfs on hda9 : 27.7925 MB/sec Note that when I first set this hardware up, I tried RAID0 on the same hardware and saw dbench 32 numbers of 76 MB/sec. So, I think the dbench number for reiserfs on md0 should be ** at least ** five times faster than it is. Are my expectations too high or is there a real problem here? (tested on 2.4.15-pre5, this problem has been around for all 2.4 kernels I've tried.) Happy to help test and debug... please send suggestions. Torrey Hoffman - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/