From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bogo Mipps Subject: Re: Advice please re failed Raid6 Date: Wed, 19 Jul 2017 13:52:59 +1200 Message-ID: References: <9dca5b7a-b60e-0e93-41fd-49d092d8b27b@gmail.com> <22892.649.826246.644975@tree.ty.sabi.co.uk> Reply-To: bogo.mipps@gmail.com Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <22892.649.826246.644975@tree.ty.sabi.co.uk> Content-Language: en-US Sender: linux-raid-owner@vger.kernel.org To: Peter Grandi , Linux Raid List-Id: linux-raid.ids On 07/17/2017 12:19 PM, Peter Grandi wrote: > The line that worries a bit is this: > > Jul 5 21:06:18 keruru mdadm[2497]: RebuildFinished event > detected on md device /dev/md0, component device mismatches > found: 1847058224 (on raid level 6) > > That seems to indicate that pretty much every block was a > mismatch. Which would have happened if you put in a blank drive > and then used '--create --assume-clean' instead of '--assemble > --force'. But '--assume-clean" explicitly skips a rebuild, and I > wonder whether you omitted that yoiu have triggered a "repair" > in 'sync_action'. Also the message is reported by 'mdadm', and > it may be that 'mdadm' was running in daemon mode and triggering > a periodic "repair". I can't remember the defaults. > > HOWEVER there is a very subtle detail: the order of the devices > from '--examine' is: 0: 'sdb', 1: 'sdc', 2: 'sdd', 3: 'sde' but > you recreated the set in a different order. The order of the > devices does not matter if they have MD superblocks,.but here > you are using '--create' to make new superblocks, and they order > must match exactly the original order. > >> root@keruru:/var/log# mdadm --create --assume-clean --level=6 --raid-devices=4 --size=1953382912 /dev/md0 /dev/sdb /dev/sde /dev/sdd /dev/sdc > > Probably the best thing you can do is to rerun this with members > "missing /dev/sdc /dev/sdd /dev/sde". and then use 'blkid /dev/md0' > to check whether the data in it is recognized again. If so add > '/dev/sdb'. I did a quick test here of something close to that > and it worked... Thanks for responding, Peter. Much appreciated. Did I do it right? (See below) root@keruru:~# mdadm --create --assume-clean --level=6 --raid-devices=4 --size=1953382912 /dev/md0 missing /dev/sdc /dev/sdd /dev/sde mdadm: /dev/sdc appears to be part of a raid array: level=raid6 devices=4 ctime=Tue Jul 11 17:33:12 2017 mdadm: /dev/sdd appears to be part of a raid array: level=raid6 devices=4 ctime=Tue Jul 11 17:33:12 2017 mdadm: /dev/sde appears to be part of a raid array: level=raid6 devices=4 ctime=Tue Jul 11 17:33:12 2017 Continue creating array? y mdadm: Defaulting to version 1.2 metadata mdadm: array /dev/md0 started. root@keruru:~# blkid /dev/md0 root@keruru:~# root@keruru:~# cat /proc/mdstat Personalities : [raid6] [raid5] [raid4] md0 : active (auto-read-only) raid6 sde[3] sdd[2] sdc[1] 3906765824 blocks super 1.2 level 6, 512k chunk, algorithm 2 [4/3] [_UUU] unused devices: No reading from blkid, so I am assuming 'not good'. But I've done nothing further in case I misunderstood your suggestion.