Hello everyone,

I have a corrupted filesystem which I can't seem to recover.

The machine is:
Debian Linux, kernel 4.9 and btrfs-progs v4.13.3

I have a HDD RAID5 with LVM and the volume in question is a LVM volume.
On top of that I had a RAID1 SSD cache with lvm-cache.

Yesterday both! SSDs died within minutes. This lead to the corruped
filesystem that I have now.

I hope I followed the procedure correctly.

What I tried so far:
* "mount -o usebackuproot,ro " and "nospace_cache" "clear_cache" and all
permutations of these mount options

I'm getting:

[96926.830400] BTRFS info (device dm-2): trying to use backup root at
mount time
[96926.830406] BTRFS info (device dm-2): disk space caching is enabled
[96926.927978] BTRFS error (device dm-2): parent transid verify failed
on 321269628928 wanted 3276017 found 3275985
[96926.938619] BTRFS error (device dm-2): parent transid verify failed
on 321269628928 wanted 3276017 found 3275985
[96926.940705] BTRFS error (device dm-2): failed to recover balance: -5
[96926.985801] BTRFS error (device dm-2): open_ctree failed

The weird thing is that I can't really find information about the
"failed to recover balance: -5" error. - There was no rebalancing
running when during the crash.

* btrfs-find-root: https://pastebin.com/qkjnSUF7 - It bothers me that I
don't see any "good generations" as described here:
https://btrfs.wiki.kernel.org/index.php/Restore

* "btrfs rescue" - it starts, then goes to "looping on XYZ" then stops

* "btrfs rescue super-recover -v" gives:

All Devices:
	Device: id = 1, name = /dev/vg00/...
Before Recovering:
	[All good supers]:
		device name = /dev/vg00/...
		superblock bytenr = 65536

		device name = /dev/vg00/...
		superblock bytenr = 67108864

		device name = /dev/vg00/...
		superblock bytenr = 274877906944

	[All bad supers]:

All supers are valid, no need to recover


* Unfortunatly I did a "btrfs rescue zero-log" at some point :( - As it
turns out that might have been a bad idea


* Also, a "btrfs  check --init-extent-tree" - https://pastebin.com/jATDCFZy

The volume contained qcow2 images for VMs. I need only one of those,
since one piece of important software decided to not do backups :(

Any help is highly appreciated.

Many thanks,
udo.