Chris Hellyar wrote, On 14/02/13 14:03:
Hi folks..
Got a bit of a conundrum...
A friend has (had) a nas box that failed a drive in a raid 5 array
during expansion of the array from 3 to 4 drives. The drive that
failed was the 'new' one..
I've got the three drives here, and managed to get mdadm to create the
array using:
mdadm --create /dev/md1 --assume-clean --level=5 --raid-devices=4
/dev/sda3 /dev/sdb3 /dev/sdc3 missing
That's the problem - you've created an array rather than --assemble
Assemble
Assemble the components of a previously created array
into an
active array. Components can be explicitly given or
can be
searched for. mdadm checks that the components do form
a bona
fide array, and can, on request, fiddle superblock
information
so as to assemble a faulty array.
Create Create a new array with per-device metadata
(superblocks).
Appropriate metadata is written to each device, and
then the
array comprising those devices is activated. A 'resync'
process
is started to make sure that the array is consistent
(e.g. both
sides of a mirror contain the same data) but the content
of the
device is left otherwise untouched.
So the data is still physically on the disk but its lost all trace of
the metadata. I'd say its probably all gone now.
You *might* have some luck with
mdadm --create /dev/md1 --assume-clean --level=5 --raid-devices=3
/dev/sda3 /dev/sdb3 /dev/sdc3
which will write metadata for a three-disk raid5 provided they're not
too far gone.
Depends how much data has moved to the new disk / how far through the
conversion it got and what the conversion actually does to the data.
Have you got enough spare disks to image the whole lot off with a dd ?
If there are any backups at all it might be easier to simply restore.
Photorec is fantastic but it won't understand how the data was broken up
on the raid, and the new raid.
fdisk says there is no valid partition on the resulting device
/dev/md1 and photorec after many hours of trying only ever recovered
some small fragments of mp3 files, some text files and some small
images...
The drives have not been written to since the failure apart from me
re-writing the superblocks per the above, but it was some what through
expanding the array so who knows what state the data was in.
I'm assuming that the small / framented files found by photorec is a
result of re-creating the array with incorrect geometry with respect
to chunk size etc.
Anyone got any hot tips for this one? I did a bit of googling and
forum reading and didn't really get all that far. The array came out
of a QNAP TS-419P which I understand is an ext3/4 filesystem
(depending on firmware version).
The other partitions of the drive when joined as arrays have the linux
OS and system files for the QNAP intact, it's just the large storage
array that's bust.
The owner is pretty much resigned to loosing the data (no backups,
duh) but it'd be nice to pull a rabbit outa the hat.
Cheers, Chris H.
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CF
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