From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Klauer Subject: Re: problems with dm-raid 6 Date: Sun, 20 Mar 2016 23:37:27 +0100 Message-ID: <20160320223727.GA29895@EIS> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Patrick Tschackert Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Sun, Mar 20, 2016 at 10:44:57PM +0100, Patrick Tschackert wrote: > After rebooting the system, one of the harddisks was missing from my md raid 6 (the drive was /dev/sdf), so i rebuilt it with a hotspare that was already present in the system. > I physically removed the "missing" /dev/sdf drive after the restore and replaced it with a new drive. Exact commands involved for those steps? mdadm --examine output for your disks? > $ cat /sys/block/md0/md/mismatch_cnt > 311936608 Basically the whole array out of whack. This is what you get when you use --create --assume-clean on disks that are not actually clean... or if you somehow convince md to integrate a disk that does not have valid data on, for example because you copied partition table and md metadata - but not everything else - using dd. Something really bad happened here and the only person who can explain it, is probably yourself. Your best bet is that the data is valid on n-2 disks. Use overlay https://raid.wiki.kernel.org/index.php/Recovering_a_failed_software_RAID#Making_the_harddisks_read-only_using_an_overlay_file Assemble the overlay RAID with any 2 disks missing (try all combinations) and see if you get valid data. Regards Andreas Klauer