From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262739AbTDNESu (for ); Mon, 14 Apr 2003 00:18:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262740AbTDNESu (for ); Mon, 14 Apr 2003 00:18:50 -0400 Received: from dialup-10.157.221.203.acc50-nort-cbr.comindico.com.au ([203.221.157.10]:65028 "EHLO chimp.local.net") by vger.kernel.org with ESMTP id S262739AbTDNESt (for ); Mon, 14 Apr 2003 00:18:49 -0400 Message-ID: <3E9A31FF.6030506@cyberone.com.au> Date: Mon, 14 Apr 2003 13:58:55 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3) Gecko/20030327 Debian/1.3-4 X-Accept-Language: en MIME-Version: 1.0 To: Chuck Ebbert <76306.1226@compuserve.com> CC: Alan Cox , Linux Kernel Mailing List Subject: Re: Benefits from computing physical IDE disk geometry? References: <200304131407_MC3-1-3441-57C7@compuserve.com> <1050272156.24559.4.camel@dhcp22.swansea.linux.org.uk> In-Reply-To: <1050272156.24559.4.camel@dhcp22.swansea.linux.org.uk> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Alan Cox wrote: >On Sul, 2003-04-13 at 19:03, Chuck Ebbert wrote: > >> OTOH you can come up with scenarios like, say, a DBMS doing 16K page >>aligned IO to raw devices where you might see big gains from making sure >>those 16K chunks didn't cross a physical cylinder boundary. >> > >You couldn't even tell where such boundaries exist, or what the real >block size of the underlying media is. Cyliners are all different sizes. > Yes this is getting very difficult as Alan said. Its also something that we can't do in kernel - the block io scheduler can only choose from what it is given. I wouldn't be surprised if big databases did try using some sorts of disk mapping systems to help optimise their IO however.