From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Robinson Subject: Re: [dm-devel] REQUEST for new 'topology' metrics to be moved out of the 'queue' sysfs directory. Date: Thu, 25 Jun 2009 12:36:15 +0100 Message-ID: <4A43612F.2000100@anonymous.org.uk> References: <19010.62951.886231.96622@notabene.brown> <125b48b7ffc99a496fbdd512f38cada5.squirrel@neil.brown.name> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "Martin K. Petersen" , Mike Snitzer , Linus Torvalds , Alasdair G Kergon , jens.axboe@oracle.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, linux-ide@vger.kernel.org, linux-fsdevel@vger.kernel.org, device-mapper development To: NeilBrown Return-path: In-Reply-To: <125b48b7ffc99a496fbdd512f38cada5.squirrel@neil.brown.name> Sender: linux-raid-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 25/06/2009 12:07, NeilBrown wrote: [...] > stripe-width is only really needed on raid4/5/6 as it is aimed at > avoiding read-modify-write, so it would be the stripe size, which would > be minimum_io_size. [...] > stride-size is used for raid0 or raid4, or the "Asymmetric" raid5 layouts. > It allows ext3 to stagger which drive certain 'hot' data structures are > on. The current metrics don't allow for that at all. > I'm not saying they should, and I'm not sure how they could. But it > is sad. Even sadder, when a raid 0/4/5/6 is reshaped over more discs (and probably other scenarios outwith md), both stripe-width and stride-size change. Is there any prospect this new stacking could give us the opportunity to tell our client (LVM, filesystem, whatever) about the change, or that they'll be able to take advantage of it? Cheers, John.