On 05/06/16 18:13, Pawel Jakub Dawidek wrote:
On Sun, Jun 05, 2016 at 06:03:53PM +0200, Arne Jansen wrote:
On 05/06/16 17:32, Pawel Jakub Dawidek wrote:
Unfortunately tools like photorec won't work (I assume the tool scans
the disk and looks for some JPEG headers, etc.) as this was RAIDZ1 pool,
so none of the disks contains recognizable data.
Are you sure? Isn't only the parity information unusable? So 2/3 of the
information should be there in plain. It would be good to revive
the broken disk, though.
Each ZFS block will be broken into two pieces. By default maximum block
size if 128kB, so on disk 0 you will find first, third, etc. 64kB chunk
of the photo. Enough to find a JPEG header, indeed, by photos are rather
larger.
damn, obviously :(
Two questions come to my mind:
1. Is it possible to recover the data now?
2. Is it possible to recover the data in theory?
I'm afraid the answer to the first question is 'no', because we are not
aware of any existing tools that could help you with the process and to
do it now you would need to find ZFS expert willing to spend some
serious amount of time, which I'm sure will cost a lot.
But if I understand your description correctly, the data is still on the
disks, so in theory it should be possible to recover it. Maybe not now,
but in 5 years? 10 years? Family memories is probably not something you
need immediately and after some time someone may develop a tool to help
recover data from the pools like yours. Even if noone will, maybe you
will become rich enough (or maybe you are already, no idea) to sponsor
development of such a tool.
Writing such a tool would be fun, but it would probably take weeks to
months to write it. The question is if there are enough broken pools to
make it worth investing the time.
When I decided to port ZFS to FreeBSD my estimation was to have a
working rad-write prototype in 6 months. It took 10 days (and nights).
You won't be able to tell until you try:)
You're right, it can't be that hard :) What would be the requirements,
from which worst-case scenario should such a tool be able to recover
the data?
- all uberblocks wiped
- all label wiped
- only the minimum amount of disks available
Can we subtract even more information and still have in theory enough
information to recover all data?
-Arne
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