From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753563AbXC0KKb (ORCPT ); Tue, 27 Mar 2007 06:10:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753555AbXC0KKb (ORCPT ); Tue, 27 Mar 2007 06:10:31 -0400 Received: from py-out-1112.google.com ([64.233.166.181]:1783 "EHLO py-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753489AbXC0KK3 (ORCPT ); Tue, 27 Mar 2007 06:10:29 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:user-agent:mime-version:to:cc:subject:references:in-reply-to:content-type:content-transfer-encoding; b=k0YWvBqmJPnHIX9dEXzwHuqSCLkZlbTe9R7W2eiNpEr6mDVjbgB0B9w+zIzy/6RZjWj/P5ttsjCp5YvVnddKBMY6FDBQH6EqdMVsP9WTtGlyvyrKV34MnTV8zRF2d2kldxeflVaOdTH+5euqhENc8QAC01kjTAZ2ne2235JQpEQ= Message-ID: <4608ED89.5040407@gmail.com> Date: Tue, 27 Mar 2007 19:10:17 +0900 From: Tejun Heo User-Agent: Icedove 1.5.0.10 (X11/20070307) MIME-Version: 1.0 To: Justin Piszcz CC: Alan Cox , linux-kernel@vger.kernel.org Subject: Re: Why is NCQ enabled by default by libata? (2.6.20) References: <20070324184300.3250fab0@the-village.bc.nu> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Justin Piszcz wrote: > Checking the benchmarks on various hardware websites, anandtech, > hothardware and others, they generally all come to the same conclusion > if there is only 1 thread using I/O (single user system) then NCQ off is > the best. Are they testing using Linux? I/O performance is highly dependent on workload and scheduling, so result on windows wouldn't be very useful. Posting some links here would be nice. > I see 30-50MB/s faster speeds with NCQ turned off on two > different SW RAID5s. You're testing raptors, right? If the performance drop is that drastic and consistent over different workloads, we'll have to disable NCQ for raptors. I'm not sure about other drives. Care to perform tests over more popular ones (e.g. recent seagates or 7200rpm wds)? -- tejun