From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751330AbWGPW5r (ORCPT ); Sun, 16 Jul 2006 18:57:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751335AbWGPW5r (ORCPT ); Sun, 16 Jul 2006 18:57:47 -0400 Received: from wr-out-0506.google.com ([64.233.184.226]:10469 "EHLO wr-out-0506.google.com") by vger.kernel.org with ESMTP id S1751330AbWGPW5q (ORCPT ); Sun, 16 Jul 2006 18:57:46 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=QILfBwqxaaj4ecHeTtaNaVcMZwbxU3jeQMSRsg1JZYlIZKqZjq1r4jhU7cqE0B09/n8kWO8ZI2E57zYgyN08Z+QNlkf1BmI+TuDmLUgrnHGjcE5DP5F0Cccc39jZxL+R7IKsOn7rqS1jD5DrV+hnSPVOE59ql7DADbR1izCV/48= Message-ID: Date: Sun, 16 Jul 2006 15:57:45 -0700 From: "Jonathan Baccash" To: "Chuck Ebbert" <76306.1226@compuserve.com> Subject: Re: raid io requests not parallel? Cc: linux-kernel In-Reply-To: <200607161609_MC3-1-C52A-F449@compuserve.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <200607161609_MC3-1-C52A-F449@compuserve.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > Because a single read not only goes to just one disk, it is sent to > the disk with the lowest expected seek time for that request. This > cuts average read time in half, on average. > > (See drivers/md/raid1.c::read_balance().) Thanks Chuck! That is making some sense, although I think I'll have to read and think about it some more before I quite understand. > You didn't post any benchmarks showing results for single write to a > single disk. I didn't think I could get any repeatable results for a single write, so I was trying to understand what is happening based on runs of longer writes.