Forum Discussion

Guide

Jan 23, 2020

Readynas 3312 BTRFS error (device md127) in __btrfs_free_extent:6998: errno=-28 No space left

Hi, I have another issue with BTRFS. All the sudden, I couldn't write to the share. It gave the exception 'Permission denied'. I also could reset the shares permissions. So i tried to rese...

defcon84

Guide

Jan 23, 2020

some more information:

root@SKNAS05:~# btrfsck /dev/md127 --force
WARNING: filesystem mounted, continuing because of --force
parent transid verify failed on 45403858534400 wanted 1820270 found 1820360
parent transid verify failed on 45403858534400 wanted 1820270 found 1820360
parent transid verify failed on 45403858534400 wanted 1820270 found 1820360
leaf parent key incorrect 45403858534400
ERROR: cannot open file system

Sandshark
Sensei
Jan 23, 2020
Yes, when there is an unrecoverable BTRFS error, one thing the OS tries is to make the volume read-only so you can make sure your backup is in order before something more happens (which likely would if writes were allowed). The only solution to this is normally a factory default and restoration of data from backup. It's a good idea to first check the SMART data for your drives just to be sure a hardware issue isn't the driving factor.
- defcon84
  Guide
  Jan 24, 2020
  Thanks for the information.
  Shouldn't a balance fix / prevent this?
  
  smartctl doesn't show anything weird.
  Anything else I can check?
  
  For now, i'll copy the whole 80TB somewhere else and reset the NAS.
  But this shouldn't be happening in a NAS, we buy them to use the RAID5, to prevent downtime.
  - StephenB
    Guru - Experienced User
    Jan 24, 2020
    defcon84 wrote:
    
    Anything else I can check?
    
    This might resolve the error:
    
    # btrfs-zero-log /dev/md127
    
    But there could be some missing or damaged files. The wanted 1820270 found 1820360 bit in the log means that there are 90 transactions in the journal that somehow didn't get written to the file system.
    
    That could be due to disk errors, a system crash, or an unexpected power cut. So perhaps check the log zip for that stuff.