From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761818AbYC0Vv4 (ORCPT ); Thu, 27 Mar 2008 17:51:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757914AbYC0Vvr (ORCPT ); Thu, 27 Mar 2008 17:51:47 -0400 Received: from mail.tmr.com ([64.65.253.246]:51347 "EHLO gaimboi.tmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755332AbYC0Vvr (ORCPT ); Thu, 27 Mar 2008 17:51:47 -0400 Message-ID: <47EC173F.4050309@tmr.com> Date: Thu, 27 Mar 2008 17:53:03 -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: Bart Van Assche CC: Chris Snook , 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: 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 Bart Van Assche wrote: > On Tue, Mar 25, 2008 at 11:00 PM, Chris Snook wrote: >> It means you shouldn't use dd as a benchmark. > > If you want to benchmark write speed, you should add > oflag=direct,dsync to the dd command line. For benchmarking read speed > you should specify iflag=direct. Or, even better, you can use xdd with > the flags -dio -processlock. > No, you want your benchmark to measure performance doing what the application does. Do unless you have an application which has been heavily Linux-ized you don't want to measure something unrelated to the application requirements. -- Bill Davidsen "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot