Re: RAID 6, 6 device array - all devices lost superblock

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contents of /proc/mdstat

root@superior:/mnt/backup# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
[raid4] [raid10]
unused devices: <none>
root@superior:/mnt/backup#



Here are the steps I ran (minus some mounting other devices and
looking around for mdadm tracks on the old os disk)

  410  DEVICES=$(cat /proc/partitions | parallel --tagstring {5}
--colsep ' +' mdadm -E /dev/{5} |grep $UUID | parallel --colsep '\t'
echo /dev/{1})
  411  apt install parallel
  412  DEVICES=$(cat /proc/partitions | parallel --tagstring {5}
--colsep ' +' mdadm -E /dev/{5} |grep $UUID | parallel --colsep '\t'
echo /dev/{1})
  413  echo $DEVICES
  414  cat /proc/partitions
  415  DEVICES=/dev/sdb /dev/sdc /dev/sdd /dev/sde /dev/sdf /dev/sdg
  416  DEVICES="/dev/sdb /dev/sdc /dev/sdd /dev/sde /dev/sdf /dev/sdg"
  417  echo $DEVICES
  418  parallel 'test -e /dev/loop{#} || mknod -m 660 /dev/loop{#} b 7
{#}' ::: $DEVICES
  419  ls /dev/loop*
  420  dc
  421  cd /mnt/backup/
  422  ls
  423  parallel truncate -s300G overlay-{/} ::: $DEVICES
  424  ls
  425  ls -la
  426  df -h
  427  parallel 'size=$(blockdev --getsize {}); loop=$(losetup -f
--show -- overlay-{/}); echo 0 $size snapshot {} $loop P 8 | dmsetup
create {/}' ::: $DEVICES
  428  ls /dev/mapper/
  429  OVERLAYS=$(parallel echo /dev/mapper/{/} ::: $DEVICES)
  430  echo $OVERLAYS
  431  dmsetup status
  432  mdadm --assemble --force /dev/md1 $OVERLAYS
  433  history
  434  dmsetup status
  435  echo $OVERLAYS
  436  mdadm --assemble --force /dev/md0 $OVERLAYS
  437  cat /proc/partitions
  438  mkdir /mnt/oldroot
  << look for inird mdadm files >>
  484  echo $OVERLAYS
  485  mdadm --create /dev/md0 --level=raid6 -n 6 /dev/mapper/sdb
/dev/mapper/sdc /dev/mapper/sdd /dev/mapper/sde /dev/mapper/sdf
/dev/mapper/sdg
  << cancelled out of 485, review instructions... >>
  486  mdadm --create /dev/md0 --level=raid6 -n 6 /dev/mapper/sdb
/dev/mapper/sdc /dev/mapper/sdd /dev/mapper/sde /dev/mapper/sdf
/dev/mapper/sdg
  487  fsck -n /dev/md0
  488  mdadm --stop /dev/md0
  489  echo $DEVICES
  490   parallel 'dmsetup remove {/}; rm overlay-{/}' ::: $DEVICES
  491  dmsetup status
  492  ls
  493  rm overlay-*
  494  ls
  495  parallel losetup -d ::: /dev/loop[0-9]*
  496  parallel 'test -e /dev/loop{#} || mknod -m 660 /dev/loop{#} b 7
{#}' ::: $DEVICES
  497  parallel truncate -s300G overlay-{/} ::: $DEVICES
  498  parallel 'size=$(blockdev --getsize {}); loop=$(losetup -f
--show -- overlay-{/}); echo 0 $size snapshot {} $loop P 8 | dmsetup
create {/}' ::: $DEVICES
  499  dmsetup status
  500  /sbin/reboot
  501  history
  502  dmsetup status
  503  mount
  504  cat /proc/partitions
  505  nano /etc/fstab
  506  mount /mnt/backup/
  507  ls /mnt/backup/
  508  rm /mnt/backup/
  509  rm /mnt/backup/overlay-sd*
  510  emacs setupOverlay &
  511  ps auxww | grep emacs
  512  kill 65017
  513  ls /dev/loo*
  514  DEVICES='/dev/sdb /dev/sdc /dev/sdd /dev/sde /dev/sdf /dev/sdg'
  515  echo $DEVICES
  516   parallel 'test -e /dev/loop{#} || mknod -m 660 /dev/loop{#} b
7 {#}' ::: $DEVICES
  517  ls /dev/loo*
  518  parallel truncate -s4000G overlay-{/} ::: $DEVICES
  519  ls
  520  rm overlay-sd*
  521  cd /mnt/bak
  522  cd /mnt/backup/
  523  ls
  524  parallel truncate -s4000G overlay-{/} ::: $DEVICES
  525  ls -la
  526  blockdev --getsize /dev/sdb
  527  man losetup
  528  man losetup
  529  parallel 'size=$(blockdev --getsize {}); loop=$(losetup -f
--show -- overlay-{/}); echo 0 $size snapshot {} $loop P 8 | dmsetup
create {/}' ::: $DEVICES
  530  dmsetup status
  531  history | grep mdadm
  532  history
  533  dmsetup status
  534  history | grep dmsetup
  535  dmsetup status
  536  dmsetup remove sdg
  537  dmsetup ls --tree
  538  lsof
  539  dmsetup ls --tre
  540  dmsetup ls --tree
  541  lsof | grep -i sdg
  542  lsof | grep -i sdf
  543  history |grep dmsetup | less
  544  dmsetup status
  545  history > ~plsander/Documents/raidIssues/joblog

On Wed, Aug 31, 2022 at 4:37 PM John Stoffel <john@xxxxxxxxxxx> wrote:
>
> >>>>> "Peter" == Peter Sanders <plsander@xxxxxxxxx> writes:
>
> > encountering a puzzling situation.
> > dmsetup is failing to return.
>
> I don't think you need to use dmsetup in your case, but can you post
> *all* the commands you ran before you got to this point, and the
> output of
>
>        cat /proc/mdstat
>
> as well?  Thinking on this some more, you might need to actually also
> add:
>
>         --assume-clean
>
> to the 'mdadm create ....' string, since you don't want it to zero the
> array or anything.
>
> Sorry for not remembering this at the time!
>
> So if you can, please just start over from scratch, showing the setup
> of the loop devices, the overlayfs setup, and the building the RAID6
> array, along with the cat /proc/mdstat after you do the initial build.
>
> John
>
> P.S.  For those who hated my email citing tool, I pulled it out for
> now.  Only citing with > now.  :-)
>
> > root@superior:/mnt/backup# dmsetup status
> > sdg: 0 5860533168 snapshot 16/8388608000 16
> > sdf: 0 5860533168 snapshot 16/8388608000 16
> > sde: 0 5860533168 snapshot 16/8388608000 16
> > sdd: 0 5860533168 snapshot 16/8388608000 16
> > sdc: 0 5860533168 snapshot 16/8388608000 16
> > sdb: 0 5860533168 snapshot 16/8388608000 16
>
> > dmsetup remove sdg  runs for hours.
> > Canceled it, ran dmsetup ls --tree and find that sdg is not present in the list.
>
> > dmsetup status shows:
> > sdf: 0 5860533168 snapshot 16/8388608000 16
> > sde: 0 5860533168 snapshot 16/8388608000 16
> > sdd: 0 5860533168 snapshot 16/8388608000 16
> > sdc: 0 5860533168 snapshot 16/8388608000 16
> > sdb: 0 5860533168 snapshot 16/8388608000 16
>
> > dmsetup ls --tree
> > root@superior:/mnt/backup# dmsetup ls --tree
> > sdf (253:3)
> >  ├─ (7:3)
> >  └─ (8:80)
> > sde (253:1)
> >  ├─ (7:1)
> >  └─ (8:64)
> > sdd (253:2)
> >  ├─ (7:2)
> >  └─ (8:48)
> > sdc (253:0)
> >  ├─ (7:0)
> >  └─ (8:32)
> > sdb (253:5)
> >  ├─ (7:5)
> >  └─ (8:16)
>
> > any suggestions?
>
>
>
> > On Tue, Aug 30, 2022 at 2:03 PM Wols Lists <antlists@xxxxxxxxxxxxxxx> wrote:
> >>
> >> On 30/08/2022 14:27, Peter Sanders wrote:
> >> >
> >> > And the victory conditions would be a mountable file system that passes a fsck?
> >>
> >> Yes. Just make sure you delve through the file system a bit and satisfy
> >> yourself it looks good, too ...
> >>
> >> Cheers,
> >> Wol




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