Environment
$ btrfs --version
btrfs-progs v4.2.1
$ uname -a
Linux [REDACTED] 4.2.1-040201-generic #201509211431 SMP Mon Sep 21 18:34:44 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
Problem
Today the controller of one of my external drives died. The disk is alright though. I cracked open the case, got the drive out and connected it via a SATA-USB interface.
Now, mounting the filesystem is not possible. Here's the message:
$ btrfs fi show
warning devid 3 not found already
Label: none uuid: bd6090df-5179-490e-a5f8-8fbad433657f
Total devices 3 FS bytes used 3.02TiB
devid 1 size 596.17GiB used 532.03GiB path /dev/sdd
devid 2 size 931.51GiB used 867.03GiB path /dev/sde
*** Some devices missing
Yes, I did bundle up three drives with very different sizes with the --single option on creating the file system. This absolutely works.
However, now:
$ mount /dev/sdd /mnt/btrfs/
mount: wrong fs type, bad option, bad superblock on /dev/sdd,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
Even following the official recommendation to mount degraded does not work. Here's a dmesg excerpt:
[ 1849.938705] BTRFS info (device sdd): allowing degraded mounts
[ 1849.938716] BTRFS info (device sdd): disk space caching is enabled
[ 1849.938720] BTRFS: has skinny extents
[ 1850.345011] BTRFS: bdev (null) errs: wr 2033, rd 1074, flush 0, corrupt 0, gen 249
[ 1854.953599] BTRFS: too many missing devices, writeable mount is not allowed
[ 1854.992299] BTRFS: open_ctree failed
I'm left with what appears to be a completely broken filesystem, although all disks are in working order. It's kind of a catch 22:
- The drive with the broken controller is recognized but will not join the btrfs filesystem.
- I can mount read-only but that doesn't allow me to add or remove disks.
Is there any way to add the "missing" disk to the filesystem manually, ideally without removing it's data content?
I'm happy to hear any ideas.
