Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757021AbYCYWrB (ORCPT ); Tue, 25 Mar 2008 18:47:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753972AbYCYWqx (ORCPT ); Tue, 25 Mar 2008 18:46:53 -0400 Received: from mail.tmr.com ([64.65.253.246]:49348 "EHLO gaimboi.tmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753932AbYCYWqw (ORCPT ); Tue, 25 Mar 2008 18:46:52 -0400 Message-ID: <47E98108.9000906@tmr.com> Date: Tue, 25 Mar 2008 18:47:36 -0400 From: Bill Davidsen User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.8) Gecko/20061105 SeaMonkey/1.0.6 MIME-Version: 1.0 To: Chris Snook CC: Emmanuel Florac , linux-kernel@vger.kernel.org Subject: Re: RAID-1 performance under 2.4 and 2.6 References: <20080325194306.4ac71ff2@galadriel.home> <47E975F8.3000702@redhat.com> In-Reply-To: <47E975F8.3000702@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2045 Lines: 45 Chris Snook wrote: > Emmanuel Florac wrote: >> I post there because I couldn't find any information about this >> elsewhere : on the same hardware ( Athlon X2 3500+, 512MB RAM, 2x400 GB >> Hitachi SATA2 hard drives ) the 2.4 Linux software RAID-1 (tested 2.4.32 >> and 2.4.36.2, slightly patched to recognize the hardware :p) is way >> faster than 2.6 ( tested 2.6.17.13, 2.6.18.8, 2.6.22.16, 2.6.24.3) >> especially for writes. I actually made the test on several different >> machines (same hard drives though) and it remained consistent across >> the board, with /mountpoint a software RAID-1. >> Actually checking disk activity with iostat or vmstat shows clearly a >> cache effect much more pronounced on 2.4 (i.e. writing goes on much >> longer in the background) but it doesn't really account for the >> difference. I've also tested it thru NFS from another machine (Giga >> ethernet network): >> >> dd if=/dev/zero of=/mountpoint/testfile bs=1M count=1024 >> >> kernel 2.4 2.6 2.4 thru NFS 2.6 thru NFS >> >> write 90 MB/s 65 MB/s 70 MB/s 45 MB/s >> read 90 MB/s 80 MB/s 75 MB/s 65 MB/s >> >> Duh. That's terrible. Does it mean I should stick to (heavily >> patched...) 2.4 for my file servers or... ? :) >> > > It means you shouldn't use dd as a benchmark. > What do you use as a benchmark for writing large sequential files or reading them, and why is it better than dd at modeling programs which read or write in a similar fashion? Media programs often do data access in just this fashion, multi-channel video capture, streaming video servers, and similar. -- Bill Davidsen "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot -- 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/