From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263021AbTDOS0F (for ); Tue, 15 Apr 2003 14:26:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262992AbTDOS0E (for ); Tue, 15 Apr 2003 14:26:04 -0400 Received: from siaab1ab.compuserve.com ([149.174.40.2]:2250 "EHLO siaab1ab.compuserve.com") by vger.kernel.org with ESMTP id S262964AbTDOSZm (for ); Tue, 15 Apr 2003 14:25:42 -0400 Date: Tue, 15 Apr 2003 14:33:51 -0400 From: Chuck Ebbert <76306.1226@compuserve.com> Subject: Re: Benefits from computing physical IDE disk geometry? To: Nick Piggin Cc: linux-kernel , linux-raid Message-ID: <200304151436_MC3-1-3487-215F@compuserve.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Nick Piggin wrote: > OK right. As far as I can see, the algorithm in the RAID1 code > is used to select the best drive to read from? If that is the > case then I don't think it could make better decisions given > more knowledge. How about if it just asks the elevator whether or not a given read is a good fit with its current workload? I saw in 2.5 where the balance code is looking at the number of pending requests and if it's zero then it sends it to that device. Somehow I think something better than that could be done, anyway. > It seems to me that a better way to layer it would be to have > the complex (ie deadline/AS/CFQ/etc) scheduler handling all > requests into the raid block device, then having a raid > scheduler distributing to the disks, and having the disks > run no scheduler (fifo). That only works if RAID1 is working at the physical disk level (which it should be AFAIC but people want flexibility to mirror partitions.) > In practice the current scheme probably works OK, though I > wouldn't know due to lack of resources here :P I've been playing with the 2.4 read balance code and have some improvements, but real gains need a new approach. (cc'd to linux-raid) -- Chuck