Broken Filesystem

["Hendrik Friedel" <hendrik@friedels.name>]

Hello,

I am helping someone here 
https://forum.openmediavault.org/index.php/Thread/29290-Harddrive-Failure-and-Data-Recovery/?postID=226502#post226502 
  to recover his data.
He is new to linux.

Two of his drives have a hardware problem.
btrfs filesystem show /dev/sda
Label: 'sdadisk1' uuid: fdce5ae5-fd6d-46b9-8056-3ff15ce9fa16
Total devices 1 FS bytes used 128.00KiB
devid 1 size 931.51GiB used 4.10GiB path /dev/sda

The 4.1GiB are way less than what was used.


We tried to mount with mount -t btrfs -o 
recovery,nospace_cache,clear_cache

[Sat Jan 18 11:40:29 2020] BTRFS warning (device sda): 'recovery' is 
deprecated, use 'usebackuproot' instead
[Sat Jan 18 11:40:29 2020] BTRFS info (device sda): trying to use backup 
root at mount time
[Sat Jan 18 11:40:29 2020] BTRFS info (device sda): disabling disk space 
caching
[Sat Jan 18 11:40:29 2020] BTRFS info (device sda): force clearing of 
disk cache
[Sun Jan 19 11:58:24 2020] BTRFS warning (device sda): 'recovery' is 
deprecated, use 'usebackuproot' instead
[Sun Jan 19 11:58:24 2020] BTRFS info (device sda): trying to use backup 
root at mount time
[Sun Jan 19 11:58:24 2020] BTRFS info (device sda): disabling disk space 
caching
[Sun Jan 19 11:58:24 2020] BTRFS info (device sda): force clearing of 
disk cache


The mountpoint does not show any data when mounted

Scrub did not help:
btrfs scrub start /dev/sda
scrub started on /dev/sda, fsid fdce5ae5-fd6d-46b9-8056-3ff15ce9fa16 
(pid=19881)

btrfs scrub status /dev/sda
scrub status for fdce5ae5-fd6d-46b9-8056-3ff15ce9fa16
scrub started at Sun Jan 19 12:03:35 2020 and finished after 00:00:00
total bytes scrubbed: 256.00KiB with 0 errors


btrfs check /dev/sda
Checking filesystem on /dev/sda
UUID: fdce5ae5-fd6d-46b9-8056-3ff15ce9fa16
checking extents
checking free space cache
cache and super generation don't match, space cache will be invalidated
checking fs roots
checking csums
checking root refs
found 131072 bytes used err is 0
total csum bytes: 0
total tree bytes: 131072
total fs tree bytes: 32768
total extent tree bytes: 16384
btree space waste bytes: 123986
file data blocks allocated: 0
referenced 0


Also btrfs restore -i -v /dev/sda /srv/dev-disk-by-label-NewDrive2 | tee 
/restorelog.txt did not help:
It came immediately back with 'Reached the end of the tree searching the 
directory'


btrfs-find-root /dev/sda
Superblock thinks the generation is 8
Superblock thinks the level is 0
It did not finish even in 54 hours

I am out of ideas. Can you give further advice?

Regards,
Hendrik