Linux Raid LVM/Synology BTRFS Repair

1. Prepare - Finnix Rescue CD.  Use rufus to burn to USB disk
2. Boot with Finnix Rescue CD
3. Drive Layout - lsbk
   NAME    MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINTS
   loop0     7:0    0 377.2M  1 loop
   /usr/lib/live/mount/rootfs/filesystem.squashfs
                                      /run/live/rootfs/filesystem.squashfs
   sda       8:0    0   3.6T  0 disk
   ├─sda1    8:1    0   2.4G  0 part
   ├─sda2    8:2    0     2G  0 part
   └─sda3    8:3    0   3.6T  0 part
   sdb       8:16   0   3.6T  0 disk
   ├─sdb1    8:17   0   2.4G  0 part
   ├─sdb2    8:18   0     2G  0 part
   └─sdb3    8:19   0   3.6T  0 part
     └─md127
             9:127  0   3.6T  0 raid1
       ├─vg1-syno_vg_reserved_area
       │   253:0    0    12M  0 lvm
       └─vg1-volume_1
           253:1    0   3.6T  0 lvm
   sdc       8:32   1  14.7G  0 disk
   └─sdc1    8:33   1  14.7G  0 part  /usr/lib/live/mount/medium
                                      /run/live/medium
   sdd       8:48   1     2G  0 disk
   ├─sdd1    8:49   1    15M  0 part
   ├─sdd2    8:50   1    30M  0 part
   └─sdd3    8:51   1     4M  0 part
   
   
   
4. SMART
1. Check smart status: smartctl -a /dev/sda
   
   
5. To get the LV (logical volume) name: lvm lvscan
   
   WARNING: PV /dev/md127 in VG vg1 is using an old PV header, modify the VG to update.
     ACTIVE            '/dev/vg1/syno_vg_reserved_area' [12.00 MiB]
   inherit
     ACTIVE            '/dev/vg1/volume_1' [3.63 TiB] inherit
   
   
6. Check if the LV is active
1. If not, change it to active - lvchange -ay /dev/vg1/volume_1
   
   
7. Check the volume  fsck /dev/vg1/volume_1
8. For BTRFS volume
1. Try to force mount first: mount -o recovery /dev/vg1/volume_1 /mnt/vol1
2. If you want to repair, it is risky and make sure you have backup:
   btrfs check --repair /dev/vg1/volume_1
   enabling repair mode
   WARNING:
   
   Do not use --repair unless you are advised to do so by a developer or an experienced user, and then only after having accepted that no fsck can successfully repair all types of filesystem corruption. Eg. some software or hardware bugs can fatally damage a volume.
   The operation will start in 10 seconds.
   Use Ctrl-C to stop it.
   10 9 8 7 6 5 4 3 2 1
   Starting repair.
   Opening filesystem to check...
Checking filesystem on /dev/vg1/volume_1
UUID: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxxx
[1/7] checking root items
parent transid verify failed on xxxxxxx wanted xxx found xxxxx
Ignoring transid failure
[2/7] checking extents
Invalid key type(BLOCK_GROUP_ITEM) found in root(202)
ignoring invalid key