Btrfs and LBA errors

[constantine <costas.magnuse@gmail.com>]

Hi everybody!

Btrfs filesystem could not be mounted because /dev/sdc1 had unreadable sectors.
It is/was  a single filesystem (not raid1 or raid0) over /dev/sda1 and
/dev/sdc1.
I wrote the unreadable sectors with hdparm but filesystem still cannot
be mounted (sectors were too early perhaps).

What should be my next step  for recovering the btrfs filesystem?


#### Analytically:

After
# smartctl -t long /dev/sdc
I got
"Extended offline   Completed: read failure   90%   19662   2176"

So LBA_of_first_error: 2176

With
# hdparm --read-sector
I found out that 2176-2183 LBA sectors were unreadable.

I wrote them with
# hdparm --write-sector
and now smartctl does not report any error.

However when I run
# btrfs fi show
I get:

Label: 'partition'  uuid: c1eb1aaf-665a-4337-9d04-3c3921aa67e0
        Total devices 2 FS bytes used 1.53TiB
        devid    2 size 1.37TiB used 195.00GiB path /dev/sda1
        *** Some devices missing


#### Complementary Information
# uname -a
Linux hostname 3.15.5-031505-generic #201407091543 SMP Wed Jul 9
19:44:36 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

#   btrfs --version
Btrfs v3.12

#   btrfs fi show
Label: 'partition'  uuid: c1eb1aaf-665a-4337-9d04-3c3921aa67e0
        Total devices 2 FS bytes used 1.53TiB
        devid    2 size 1.37TiB used 195.00GiB path /dev/sda1
        *** Some devices missing

Btrfs v3.12

# btrfs fi df /mnt/partition
ERROR: couldn't get space info - Inappropriate ioctl for device
ERROR: get_df failed Inappropriate ioctl for device