Btrfs Error on external disk

Hello

Just tried to reboot nextcloudpi and my external disk is not able to mount.

Error:
2959.054409] BTRFS error (device sda1): bad tree block start, want 1048576 have 0
[ 2959.054440] BTRFS error (device sda1): failed to read chunk root
[ 2959.055694] BTRFS error (device sda1): open_ctree failed

Just tried:
Btrfs rescue super-recover /dev/sda1
It says: All supers are valid, no need to recover

Then tried:
btrfs rescue chunk-recover /dev/sda1
It’s still Scanning:
Scanning: 60890370048 in dev0

Is there anything else I can do? Or just wait cause its an 1TB disk

Even after the scan an then reboot I got the same error. Any help???

i fear not.
are you using a 2,5" disk connected to USB3? I’ve had many of those cause troubles with btrfs (only) and wasted lots of time trying to fix the fs. if your data is valuable grab a rescue-image of the disk first and do all the (experimental) btrfs-recovery stuff on that; if you can mount the disk ro you can (probably) still copy the data.
if you do chunk-recover you will have to wait for it to finish; but after that scrub will still show (unrecoverable) errors or fail and balance will most likely not be possible.
in my experience the fastest way is to copy all data and re-create a new btrfs on the disk; you might check the disk itself with badblocks and smartctl before.
GOOD LUCK!

If i try to mount it - that doesn´t work:
pi@nextcloudpi:/media $ sudo mount -t btrfs -o ro,usebackuproot /dev/sda1 /media/nvme/
mount: /media/nvme: wrong fs type, bad option, bad superblock on /dev/sda1, missing codepage or helper program, or other error.

pi@nextcloudpi:/media $ sudo mount -t btrfs -o rootflags=recovery,nospace_cache /dev/sda1 /media/nvme/
mount: /media/nvme: wrong fs type, bad option, bad superblock on /dev/sda1, missing codepage or helper program, or other error.

fdisk -l shows:
Disk /dev/sda: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Disk model:
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 7B0D5C6A-7899-4148-BC31-794823F4C0AB

Device Start End Sectors Size Type
/dev/sda1 2048 1953523711 1953521664 931.5G Linux filesystem

Is it not possible to backup my data now?

pi@nextcloudpi:/media $ sudo btrfs rescue zero-log /dev/sda1
checksum verify failed on 1048576 found 000000B6 wanted 00000000
checksum verify failed on 1048576 found 000000B6 wanted 00000000
bad tree block 1048576, bytenr mismatch, want=1048576, have=0
ERROR: cannot read chunk root
ERROR: could not open ctree

I hope i can get my data back :slight_smile: i´m now very afraid that i have executed yesterday the dd comand not correctly during my read/write test. … oh my god:-(
is it anyhow possible to recover the data ? I´m not sure if i have executed wrong command, but it could be possible…