From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Bowes Subject: Re: migrating raid-1 to different drive geometry ? Date: Tue, 25 Jan 2005 08:22:07 +0000 Message-ID: References: <20050124145910.GC29766@kaneda> <16885.31484.125772.316987@cse.unsw.edu.au> <41F598BC.3040805@h3c.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <41F598BC.3040805@h3c.com> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Mike Hardy wrote: > > I'd missed the mdadm --grow feature as well, so I checked into it. > > It is only capable of increasing size on raid5, not component count. The > specific use case used as an example is that you slowly retire component > drives and the replacements are larger. When all components are the > larger size, you can grow the raid5 array to use the full size of the > device, followed by a filesystem expansion to use the grown array. > > That makes sense, given the disk layout of raid5 - its not hard to add > more stripes on the end of components, but adding new components > requires each stripe to change significantly. > > To grow component count on raid5 you have to use raidreconf, which can > work, but will toast the array if anything goes bad. I have personally > had it work, and not work, in different instances. The failures were not > necessarily raidreconf's fault, but its not fault tolerant is the point, > as it starts at the first stripe, laying things out the new way, and if > it doesn't finish, and finish correctly, you are in an irretrievable > inconsistent state. > Bah, too bad. I don't need it yet, but at some stage I'd like to be able to add another 250GB drive(s) to me array and grow the array to use the additional space in a safe/failsafe way. Perhaps by the time I come to need it this might be possible? R. -- http://robinbowes.com