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Background I had a 3.0TB die on me recently and it was in a linux raid in a Synology NAS with RAID 1 redundancy. I recently bought two 8.0TB drives and I wanted to backup the 3.0TB but my synology keeps shutting down randomly and was having senior moments. To fix this I put all the drives into my computer which is running Linux Mint 18.x Live. I'm trying to mount both raids so I can rsync the 3.0TB onto the 8.0TB raid.

Problem I can't rebuild any of the raids and hence access any of the drives. My fidsk -l output is as such:

mint ~ # fdisk -l
Disk /dev/loop0: 1.5 GiB, 1618886656 bytes, 3161888 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/nvme0n1: 477 GiB, 512110190592 bytes, 1000215216 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: DB2D71AC-EF2C-4540-A8E5-03C5D8F72D01

Device             Start        End   Sectors   Size Type
/dev/nvme0n1p1        40     409639    409600   200M EFI System
/dev/nvme0n1p2    409640  552935535 552525896 263.5G Apple HFS/HFS+
/dev/nvme0n1p3 552935536  554205071   1269536 619.9M Apple boot
/dev/nvme0n1p4 554205184  554237951     32768    16M Microsoft reserved
/dev/nvme0n1p5 554237952 1000214527 445976576 212.7G Microsoft basic data


Disk /dev/sda: 7.3 TiB, 8001563222016 bytes, 15628053168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 0A352E59-20D3-4471-AE03-F44E1C73E3EE

Device       Start         End     Sectors  Size Type
/dev/sda1     2048     4982527     4980480  2.4G Linux RAID
/dev/sda2  4982528     9176831     4194304    2G Linux RAID
/dev/sda5  9453280 15627846239 15618392960  7.3T Linux RAID


Disk /dev/sdb: 2.7 TiB, 3000592982016 bytes, 5860533168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: FDB68AFA-6AA2-4AFF-B950-A65803C3E831

Device       Start        End    Sectors  Size Type
/dev/sdb1      256    4980735    4980480  2.4G Linux RAID
/dev/sdb2  4980736    9175039    4194304    2G Linux RAID
/dev/sdb3  9437184 5860328351 5850891168  2.7T Linux RAID


Disk /dev/sdc: 7.3 TiB, 8001563222016 bytes, 15628053168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 655B6D2C-8FDB-40B2-8A57-4A4C6CEA81FA

Device       Start         End     Sectors  Size Type
/dev/sdc1     2048     4982527     4980480  2.4G Linux RAID
/dev/sdc2  4982528     9176831     4194304    2G Linux RAID
/dev/sdc5  9453280 15627846239 15618392960  7.3T Linux RAID


Disk /dev/sdd: 465.8 GiB, 500107862016 bytes, 976773168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: AB7A0C0E-F0F0-4169-A6CC-AFD36D13706B

Device      Start       End   Sectors   Size Type
/dev/sdd1      40    409639    409600   200M EFI System
/dev/sdd2  409640 976510983 976101344 465.5G Apple HFS/HFS+


Disk /dev/sde: 14.9 GiB, 16008609792 bytes, 31266816 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 112D01E3-9B10-4E53-831E-6122DE30212F

Device      Start      End  Sectors  Size Type
/dev/sde1      40   409639   409600  200M EFI System
/dev/sde2  409640 31004631 30594992 14.6G Apple HFS/HFS+


Disk /dev/sdf: 3.8 GiB, 4026531840 bytes, 7864320 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: C0FCDDB9-DB52-4F40-8615-EB3CE0E2D4F4

Device     Start     End Sectors  Size Type
/dev/sdf1   2048 7864286 7862239  3.8G Microsoft basic data

The only drives important are /dev/sda, /dev/sdb, /dev/sdc

Things I've Attempted

mdadm -Asf && vgchange -ay as per recommendation of the Synology website returns

mdadm: Devices UUID-f2e5c234:6e894003:d490d253:6ab62f4d and UUID-f8782d0e:605a2e0e:4c50beb7:39f5970b have the same name: /dev/md/2

mdadm: Duplicate MD device names in conf file were found.

Good ol' mdadm --assemble --scan returns the same.

I have also tried mdadm --stop /dev/sdb as I read here. To sum it up they said that mdadm is possesive of the drive so you can't mount it normally but since it's one drive you can destory the mdadm raid metadata and mount it normally. This code returned

mdadm --stop /dev/sdb
mdadm: /dev/sdb does not appear to be an md device

Trying to mount a single drive independently with mdadm -A /dev/sdb returns:

mdadm: /dev/sdb does not appear to be an md device

Why I think things aren't broken I've had success mounting the 3.0 TB /dev/sdb drive in the past when it's dead brother was plugged in as well. In those cases mdadm just said it built the array with one drive. I know these 8.0TB drives work because I just pulled them from my Synology server, although, they were not in a RAID 1 configuration but in a Synology Hybrid RAID, I don't know if that makes a difference.

What I think the problem is I honestly believe (in my incredibly limited experience) that the issue comes from two RAID arrays being in the same machine at once and that's confusing mdadm. I think the solution might have to do with editing /etc/mdadm.conf to specify which RAID belongs to which and then try assembling again. I am however niffed that independently trying to reconstruct the array says the drive does not to appear to be an md device. So now I don't know what to do.

  • 1
    That error message (have the same name) refers to an error in your mdadm.conf, you don't need this config file to assemble RAID so you could just get rid of it entirely, then do it properly later. – frostschutz Dec 4 '17 at 10:44
  • As for --stop /dev/sdb that's normal, you can only stop md devices (/dev/md*). Check /proc/mdstat or lsblk to see which md devices you have. If mdstat is empty then you have none, already stopped or never assembled in the first place. – frostschutz Dec 4 '17 at 10:46
  • Do it manually? mdadm --assemble /dev/md9 /dev/sda5 /dev/sdc5 and mdadm --assemble /dev/md8 /dev/sdb3 missing ? I can't remember the syntax exactly... – ilkkachu Dec 4 '17 at 11:25
  • Manually assembling the drives worked. The syntax was just mdadm --assemble /dev/sda5 /dev/sdc5 if I remember correctly. To assemble the /dev/sdb I created mdadm.conf and then deleted it's contents and it worked suddenly. Thank you. – MilesConn Dec 5 '17 at 2:26

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