BTRFS won't mount in degraded mode

BTRFS won't mount in degraded mode

[bobbygiraffe]

I'm running a BTRFS filesystem with 8 devices. I believe the data was setup in RAID5 mode, and the metadata was RAID1. Each drive is encrypted with luks, and decrypted on boot with /etc/crypttab. Recently I had a drive fail and completely stop working, and the system stopped booting (presumably because /etc/crypttab was failing). When the drive finally arrived, I took out the broken one and connected the new one.

My intention was to mount the filesystem in degraded mode and then use btrfs replace to replace the old missing drive with the new drive. However, I've been unable to mount them.

Here's my setup:

uname -a
Linux bob 5.13.19-2-pve #1 SMP PVE 5.13.19-4 (Mon, 29 Nov 2021 12:10:09 +0100) x86_64 GNU/Linux

btrfs --version
btrfs-progs v5.10.1

btrfs fi show
bad tree block 30638080, bytenr mismatch, want=30638080, have=0
bad tree block 860242231296, bytenr mismatch, want=860242231296, have=0
ERROR: failed to read block groups: Input/output error
Label: 'BTRFS'  uuid: 76ce90e7-8225-4a34-90e1-2d35e0f4e89a
        Total devices 8 FS bytes used 26.80TiB
        devid    2 size 3.64TiB used 3.06TiB path /dev/mapper/HDDC
        devid    3 size 7.28TiB used 5.52TiB path /dev/mapper/HDDH
        devid    4 size 7.28TiB used 6.32TiB path /dev/mapper/HDDF
        devid    5 size 7.28TiB used 6.73TiB path /dev/mapper/HDDE
        devid    6 size 3.57TiB used 519.00GiB path /dev/mapper/HDDJ
        devid    7 size 3.64TiB used 593.06GiB path /dev/mapper/HDDG
        devid    8 size 3.64TiB used 594.00GiB path /dev/mapper/HDDD
        *** Some devices missing


The command I tried:
mount -t btrfs -o degraded /dev/mapper/HDDD /mnt/btrfs

Resulting in:

[  306.632524] BTRFS info (device dm-15): flagging fs with big metadata feature
[  306.632528] BTRFS info (device dm-15): allowing degraded mounts
[  306.632530] BTRFS info (device dm-15): disk space caching is enabled
[  306.632531] BTRFS info (device dm-15): has skinny extents
[  306.658947] BTRFS warning (device dm-15): devid 1 uuid b3429c81-83cc-4401-8e18-a85d89e320fd is missing
[  307.225260] BTRFS warning (device dm-15): failed to read root (objectid=9): -5
[  307.232646] BTRFS error (device dm-15): open_ctree failed

I have also checked
 btrfs rescue super-recover -v /dev/mapper/HDDD
All Devices:
        Device: id = 7, name = /dev/mapper/HDDG
        Device: id = 4, name = /dev/mapper/HDDF
        Device: id = 5, name = /dev/mapper/HDDE
        Device: id = 2, name = /dev/mapper/HDDC
        Device: id = 3, name = /dev/mapper/HDDH
        Device: id = 6, name = /dev/mapper/HDDJ
        Device: id = 8, name = /dev/mapper/HDDD

Before Recovering:
        [All good supers]:
                device name = /dev/mapper/HDDG
                superblock bytenr = 65536

                device name = /dev/mapper/HDDG
                superblock bytenr = 67108864

                device name = /dev/mapper/HDDG
                superblock bytenr = 274877906944

                device name = /dev/mapper/HDDF
                superblock bytenr = 65536

                device name = /dev/mapper/HDDF
                superblock bytenr = 67108864

                device name = /dev/mapper/HDDF
                superblock bytenr = 274877906944

                device name = /dev/mapper/HDDE
                superblock bytenr = 65536

                device name = /dev/mapper/HDDE
                superblock bytenr = 67108864

                device name = /dev/mapper/HDDE
                superblock bytenr = 274877906944

                device name = /dev/mapper/HDDC
                superblock bytenr = 65536

                device name = /dev/mapper/HDDC
                superblock bytenr = 67108864

                device name = /dev/mapper/HDDC
                superblock bytenr = 274877906944

                device name = /dev/mapper/HDDH
                superblock bytenr = 65536

                device name = /dev/mapper/HDDH
                superblock bytenr = 67108864

                device name = /dev/mapper/HDDH
                superblock bytenr = 274877906944

                device name = /dev/mapper/HDDJ
                superblock bytenr = 65536

                device name = /dev/mapper/HDDJ
                superblock bytenr = 67108864

                device name = /dev/mapper/HDDJ
                superblock bytenr = 274877906944

                device name = /dev/mapper/HDDD
                superblock bytenr = 65536

                device name = /dev/mapper/HDDD
                superblock bytenr = 67108864

                device name = /dev/mapper/HDDD
                superblock bytenr = 274877906944

        [All bad supers]:

All supers are valid, no need to recover

Another thing I have tried is
btrfs rescue zero-log /dev/mapper/HDDD

bad tree block 30638080, bytenr mismatch, want=30638080, have=0
bad tree block 31965184, bytenr mismatch, want=31965184, have=0
ERROR: could not open ctree

Any ideas on what to try next would be appreciated.