Re: Unable to mount/restore partition after eSATA fail

On Sun, Aug 26, 2012 at 4:22 PM, Stefan Harwarth
[off-list ref] wrote:

Hi cwillu,

thanks for the quick reply. I didn't realize that my debian 6 was shipping
such an old btrfs/kernel package - though I should have known better :(

Anyways I already tried to recover my files with an Ubuntu 12.04 (Kernel
3.2) and following your recommendation, I upgraded to 3.5 and tried btrfsck,
btrfs-restore and btrfs-find-root on /dev/sdb as well as the partition
/dev/sdb1 but I only got "no btrfs filesystem" and "could not open root,
trying backup super" (for btrfs-restore).

I haven't tried -o recovery yet, but it looks to me like there's no starting
point at all for the tools (which brings me back to the 6.4meg of NULL-bytes
at the start of the partition).

So is there any chance on recovering FS information, from what I read in
wikipedia btrfs stores some copies of important FS metadata throughout the
partition.

-o recovery will try the various copies of the superblock; hopefully
you haven't used "btrfs-select-super" at any point, as it works by
overwriting those copies with the selected one (i.e., you get one
shot).

I believe btrfs doesn't write to the first couple mb of the partition,
so the existence of gibberish or empty bytes there doesn't indicate a
problem; more worrisome is that it isn't actually being detected as
btrfs.  Can you describe the setup (partitions in the filesystem, etc)
a bit more, and possibly include a dmesg from after an attempt to
mount it under 3.5?