btrfs Unmountable: not mounted

[kenig]

Hi!

I recently set up an unraid server and after some fiddling managed to get it working. Today I installed a new CPU fan and after starting up the array couldnt start all drives anymore.

My setup:

12 TB parity (sdb)

12 TB data (sdc)

8TB data (sde)

256GB cache SSD (sda)

 

the 12TB isn't mounting anymore. I get Unmountable: not mounted. 

After checking some forum posts I tried btrfs fi show and get both my 12TB drives with the same uuid:

root@Tower:~# btrfs fi show /dev/sde1
WARNING: adding device /dev/sdc1 gen 2016 but found an existing device /dev/sdb1 gen 2032
ERROR: cannot scan /dev/sdc1: File exists
WARNING: adding device /dev/md1 gen 2016 but found an existing device /dev/sdb1 gen 2032
ERROR: cannot scan /dev/md1: File exists
Label: none  uuid: 0b6913ce-61b3-4b16-9a03-3a82f0ef306b
        Total devices 1 FS bytes used 144.00KiB
        devid    1 size 7.28TiB used 2.02GiB path /dev/md2

root@Tower:~# btrfs fi show /dev/sda1
WARNING: adding device /dev/sdc1 gen 2016 but found an existing device /dev/sdb1 gen 2032
ERROR: cannot scan /dev/sdc1: File exists
WARNING: adding device /dev/md1 gen 2016 but found an existing device /dev/sdb1 gen 2032
ERROR: cannot scan /dev/md1: File exists
ERROR: not a valid btrfs filesystem: /boot
root@Tower:~# btrfs fi show /dev/sdb1
WARNING: adding device /dev/sdc1 gen 2016 but found an existing device /dev/sdb1 gen 2032
ERROR: cannot scan /dev/sdc1: File exists
WARNING: adding device /dev/md1 gen 2016 but found an existing device /dev/sdb1 gen 2032
ERROR: cannot scan /dev/md1: File exists
Label: none  uuid: 49d47325-9269-4f32-a2b3-6539ff1be045
        Total devices 1 FS bytes used 5.31TiB
        devid    1 size 10.91TiB used 5.33TiB path /dev/sdb1

root@Tower:~# btrfs fi show /dev/sdc1
Label: none  uuid: 49d47325-9269-4f32-a2b3-6539ff1be045
        Total devices 1 FS bytes used 5.31TiB
        devid    1 size 10.91TiB used 5.33TiB path /dev/md1

 

The 8TB device is empty (3.7MB of 8TB used)

I tried different SATA Ports. Unfortunately it made things more confusing as parity and data disk started switching places. Now I dont know which one is which.

Can I use btrfstune -u /dev/sdc1 to get a new uuid for it? Is my data on that disk still available after that?

Any help would be greatly appreciated!

Edited July 9, 2021 by kenig

[JorgeB]

Please post the diagnostics: Tools -> Diagnostics (after array start)

[kenig]

Here you go

tower-diagnostics-20210709-1036.zip

[JorgeB]

Sometimes with few data disks (or an odd number of data disks), parity can appear to have a valid filesystem, this can happen with any filesystem but it's particularly a problem with btrfs since it scans for all filesystems at boot, and then it gets confused, solution here would be to use parity2 slot instead, the way it's calculated would make it impossible, or at least very unlikely, that a valid filesystem could be detected there, you'd need to unassign parity, wipe it with:

wipefs -a /dev/sdb1

Reboot, then assign it as parity2 and let it sync.

[kenig]

Thanks! Is there a way to tell which disk has been parity and which one was data?

The problematic disc is sdc (12TB data drive) at the moment. I fear loosing data if I wipe parity and the drive has failed too.

I tried mounting both with "Unassigned Drives" Plugin but neither could be mounted.

Jul 9 11:44:39 Tower unassigned.devices: Mount drive command: /sbin/mount -t btrfs -o rw,auto,async,noatime,nodiratime '/dev/sdc1' '/mnt/disks/WDC_WD120EDAZ-11F3RA0_5PJHXG4C_2'
Jul 9 11:44:39 Tower unassigned.devices: Mount of '/dev/sdc1' failed: 'mount: /mnt/disks/WDC_WD120EDAZ-11F3RA0_5PJHXG4C_2: mount(2) system call failed: File exists. '

 

Edited July 9, 2021 by kenig
more info

[JorgeB]

It's normal not mounting with UD because of the same reason, If you want to make sure all is well before wiping parity just disconnect parity from the server and after booting disk1 should now mount.

[kenig]

Ok, will do that and then wipe parity if data is ok

[kenig]

Data is ok. Will have to wait to rebuild parity until tonight. Need the array for work atm.

Thanks a lot for that perfect support!