Btrfs transid failure

Question

I can't mount my Btrfs volume any more. It says:

mount: wrong fs type, bad option, bad superblock on /dev/md0p1,
       missing codepage or helper program, or other error

       In some cases useful info is found in syslog - try
       dmesg | tail or so.

dmesg | grep BTRFS
    [    2.596762] BTRFS: device label DATA devid 1 transid 311913 /dev/md0p1
    [   98.707993] BTRFS warning (device md0p1): 'recovery' is deprecated, use 'usebackuproot' instead
    [   98.707995] BTRFS info (device md0p1): trying to use backup root at mount time
    [   98.707997] BTRFS info (device md0p1): disabling disk space caching
    [   98.707998] BTRFS info (device md0p1): has skinny extents
    [   98.915571] BTRFS error (device md0p1): parent transid verify failed on 29458432 wanted 5 found 311913
    [   98.937552] BTRFS error (device md0p1): parent transid verify failed on 29458432 wanted 5 found 311913
    [   98.990667] BTRFS error (device md0p1): open_ctree failed

dmesg | grep transid
    [    2.596762] BTRFS: device label DATA devid 1 transid 311913 /dev/md0p1
    [   98.915571] BTRFS error (device md0p1): parent transid verify failed on 29458432 wanted 5 found 311913
    [   98.937552] BTRFS error (device md0p1): parent transid verify failed on 29458432 wanted 5 found 311913

I tried btrfs-zero-log but it doesn't helped. I don't know what to do :/ And I didn't found any useful articel on the Internet.

Maybe you can help me. Thanks in advantage.

Answer 1

Your error might be part of the parity raid (5/6) Gotchas, see THIS link:

Parity RAID

Currently raid5 and raid6 profiles have flaws that make it strongly not recommended as per the Status page.
    {..}
    If a crash happens while a raid5/raid6 volume is being written this can result in a "transid" mismatch as in transid verify failed.
    The resulting corruption cannot be currently fixed. 

In which case there is no way to repair the damage done to your Raid. Did you use BTRFS Raid 5/6 ?

According to THIS link, it might still be possible to restore the data using:

sudo btrfs restore -sxmSv /dev/md0p1 ~/Backup/

For a list of all options, use 'btrfs restore --help'