From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chuck Ebbert <76306.1226@compuserve.com> Subject: Re: Benefits from computing physical IDE disk geometry? Date: Tue, 15 Apr 2003 14:33:51 -0400 Sender: linux-kernel-owner@vger.kernel.org Message-ID: <200304151436_MC3-1-3487-215F@compuserve.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline To: Nick Piggin Cc: linux-kernel , linux-raid List-Id: linux-raid.ids 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