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Ok so I have a 2 TB raid 1 setup that has three partitions:

  • sdc1: linux
  • sdc2: swap
  • sdc3: LVM for data

However the LVM will no longer mount. So I thought that I would take the first drive, mount it in linux (ive done this b4), and reset the spare drive to copy the data.

Normally I can mount a single drive for data recovery using:

sudo su
apt-get install mdadm lvm2
mdadm --assemble --scan
modprobe dm-mod
vgscan
vgchange -ay c
mount -o ro /dev/c/c /mnt

Unfortunately, vgscan doesnot recognize the data partition. It appears as though the superblock on the first drive's data partition was erased while syncing with the second. So now I cannot mount that partition and the second drive is stuck in spare mode.

Any ideas? Or a way to force mount the data partition just to copy the data?

knoppix@Microknoppix:~$ sudo su
root@Microknoppix:/home/knoppix# apt-get install mdadm lvm2
Reading package lists... Done
Building dependency tree       
Reading state information... Done
lvm2 is already the newest version.
mdadm is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 551 not upgraded.
root@Microknoppix:/home/knoppix# mdadm --assemble --scan
   mdadm: /dev/md/1 has been started with 1 drive (out of 2).
mdadm: /dev/md/0 has been started with 1 drive (out of 2).
root@Microknoppix:/home/knoppix# modprobe dm-mod
root@Microknoppix:/home/knoppix# vgscan
  Reading all physical volumes.  This may take a while...
  No volume groups found
root@Microknoppix:/home/knoppix# cat /proc/mdstat
Personalities : [raid1] 
md0 : active raid1 sdc1[2]
      4193268 blocks super 1.2 [2/1] [U_]

md1 : active raid1 sdc2[2]
      524276 blocks super 1.2 [2/1] [U_]

unused devices: <none>
root@Microknoppix:/home/knoppix# mdadm -v --assemble --auto=yes /dev/md2 /dev/sdc3
mdadm: looking for devices for /dev/md2
mdadm: no recogniseable superblock on /dev/sdc3
mdadm: /dev/sdc3 has no superblock - assembly aborted
root@Microknoppix:/home/knoppix# dumpe2fs /dev/md0 | grep -i superblock
dumpe2fs 1.42.4 (12-Jun-2012)
  Primary superblock at 0, Group descriptors at 1-1
  Backup superblock at 32768, Group descriptors at 32769-32769
  Backup superblock at 98304, Group descriptors at 98305-98305
  Backup superblock at 163840, Group descriptors at 163841-163841
  Backup superblock at 229376, Group descriptors at 229377-229377
  Backup superblock at 294912, Group descriptors at 294913-294913
  Backup superblock at 819200, Group descriptors at 819201-819201
  Backup superblock at 884736, Group descriptors at 884737-884737
root@Microknoppix:/home/knoppix#

Notes:

  • I can read the super block from the spare drive.
  • I was gonna try and restore the superblock from one of the backups, but i dont know how or if this would work.
  • I also heard creating a new array (mdadm --create) using the same parameters will not delete the data on the drive but i didnt want to risk it. Recommendations?
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