Re: Two partitionless BTRFS drives no longer seen as containing BTRFS filesystem

[evan d <forumscollective@gmail.com>]

> None of your super blocks has correct magic.


I take it this applies to both drives?



> This means either your whole disk get corrupted, or something introduced
> some offset.
>
> Please try the following commands to dump more data around super blocks,
> so we could be able to find the possible offset:
>
> # dd if=/dev/sdb of=possible_sb_range.raw bs=1M count=128
> # grep -obUaP "\x5F\x42\x48\x52\x66\x53\x5F\x4D" possible_sb_range.
>
> For a valid btrfs without any offset, the result should look like:
> 65600:_BHRfS_M
> 67108928:_BHRfS_M

# dd if=/dev/sdc of=possible_sb_range.sdc.raw bs=1M count=128
128+0 records in
128+0 records out
134217728 bytes (134 MB, 128 MiB) copied, 0.737479 s, 182 MB/s

# dd if=/dev/sdb of=possible_sb_range.sdb.raw bs=1M count=128
128+0 records in
128+0 records out
134217728 bytes (134 MB, 128 MiB) copied, 0.726327 s, 185 MB/s

# grep -obUaP "\x5F\x42\x48\x52\x66\x53\x5F\x4D" possible_sb_range.sdb.raw
# grep -obUaP "\x5F\x42\x48\x52\x66\x53\x5F\x4D" possible_sb_range.sdc.raw

Both return nothing.

Both drives pass S.M.A.R.T. testing so I'd have to think the
corruption stems from some kind of offset rather than random
corruption.  They may have accidentally been inserted into a Windows
machine (but not partitioned or formatted).  Could this be a likely
cause?