From mboxrd@z Thu Jan 1 00:00:00 1970 From: Henrik Holst Subject: Re: Is shrinking raid5 possible? Date: Wed, 22 Nov 2006 21:40:35 +0100 Message-ID: <4564B5C3.9050501@idgmail.se> References: <44960C45.9050407@anu.edu.au> <17558.10906.59066.196870@cse.unsw.edu.au> <449B3A80.4070602@tmr.com> <17563.17224.85968.572754@cse.unsw.edu.au> <17567.36792.303403.35943@cse.unsw.edu.au> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Christian Pernegger wrote: >> This is shrinking an array by removing drives. We were talking about >> shrinking an array by reducing the size of drives - a very different >> think. > > Yes I know - I just wanted to get this in as an alternative shrinking > semantic. > > As for reducing the RAID (partition) size on the individual drives I > can only see two reasons: > > 1) One wants to replace / add a disk but the new disk is slightly > smaller than the existing ones. Actual capacity varies a lot for the > same nominal capacity, especially across brands. > > 2) One wants to do something else with some of the space, although for > a RAID5 I don't quite see the point - you'd end up with n small > partitions. Shrinking a 2-way mirror or stripe this way sounds far > more useful. > > Having RAID tightly integrated with volume management and partitions > would be nice, but that's a pipe dream. (EVMS just integrates the UI > somewhat, you still have to mess about with layers.) > >> I'm not sure it is really worth the effort I'm afraid. > > Neither am I ... it just would have come in handy a few times, that's all. > > Thanks, > > C. I have an 8x120 GB RAID-5 volume. Or rather. But since of yesterday I only have 7 120 GB harddrives. Since 120 GB disks are out of the "priceworthy segment" for storage I want to reduce this to a non-degenerate 7x120 GB RAID and not buy a relative expensive 120 GB disk. And recreating the RAID as a 7x120 volume is out of the question since I don't have the extra storage to move ~700 GB of data. I think there IS an application for shrinking RAID:s, as well as growing- and that is not only one of "symmetric beauty". Is such a feature within the scope of software raid development? (I guess I'm asking Neil B. or Steinar H. G.) /Henrik Holst