From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre Wieser Subject: Migrating a RAID 5 from 4x2TB to 3x6TB ? Date: Mon, 8 Jun 2015 21:28:43 +0200 (CEST) Message-ID: <167089395.613.1433791723592.JavaMail.zimbra@wieser.fr> References: <1419435054.589.1433790714774.JavaMail.zimbra@wieser.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1419435054.589.1433790714774.JavaMail.zimbra@wieser.fr> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi all, I currently have an almost full RAID 5 built with 4 x 2 TB disks. I wonder if it would be possible to migrate it to a bigger RAID 5 with 3 x 6TB new disks. I've imagined something like that : - successively fail, remove a 2TB disk, add a 4TB disk, wait for end of recovery on three 2TB disks - at the end of this first phase, I have the same ~6TB RAID 5 clean group with 3 x 4TB + 1 x 2TB disks - declare the last 2 TB disk faulty and remove it - the RAID 5 group state goes to clean, degraded - grow the RAID 5 group with --size=max option - grow the RAID 5 group with --array-size=~12TB option - last, grow the RAID 5 group with --raid-devices=3 and --backup-file=... options. And I have tested it on a small test RAID 5 group. As expected, this last command makes the RAID 5 group begins a reshaping operation. But this one keeps stucked at zero. So I have several questions : - is it even theorically possible to grow a RAID 5 while decreasing the number of disks ? - do you think the sequence i've imagined is correct ? - why the reshaping operation does it stuck at zero ? Any help or hint would be greatly appreciated :) Thanks Regards Pierre