2015-12-14 13:55 GMT+01:00 Phil Turmel [off-list ref]:

On 12/14/2015 07:03 AM, TheGerwazy . wrote:

quoted

Hi  Phil
Thanks for the message .... but,
In the last version of mdadm I get:

./mdadm --create --raid-devices=8 --level=6 --assume-clean /dev/md7
/dev/mapper/ovsdb1:1024 /dev/mapper/ovsdc1:4096
/dev/mapper/ovsdd1:1024 /dev/mapper/ovsde1:1024
/dev/mapper/ovsdf1:1024 /dev/mapper/ovsdg1:1024
/dev/mapper/ovsdh1:1024 /dev/mapper/ovsdi1:4096
mdadm: cannot open /dev/mapper/ovsdb1:1024: No such file or directory

The final version of that feature requires --data-offset=variable before
the :offset syntax is recognized on the devices.

quoted

sudo ./mdadm --create --raid-devices=8 --level=6 --assume-clean

quoted

mdadm: array /dev/md7 started.

You're committed now.  I hope it works out for you.

quoted

BTW is it possible to find right data offset without superblock on drive ?

Only if the content of that member device has searchable content in a
predictable location.  In practice that means finding the offset of the
first member by locating filesystem magic, or otherwise locating the
transition from all zeros to randomish data.

Good luck.

Phil

"Good Luck" seems to be working ... ;)

I finally recovered files with magic cmd:

sudo ./mdadm --create --raid-device=8 --level=6 --assume-clean
--size=974508544 /dev/md7 /dev/mapper/ovsde2:1024
/dev/mapper/ovsdh1:100352 /dev/mapper/ovsdg1:100352
/dev/mapper/ovsdc1:131072 /dev/mapper/ovsda1:1024
/dev/mapper/ovsdb1:1024 /dev/mapper/ovsdf1:131072
/dev/mapper/ovsdd1:100352


The main problem is the data offsets are not stored elsewhere than in
superblock. I have some drives from debian 6.0.5 and some were changed
in debian 7.5. In 6.0.5 default data offset was at 2048 sector while
int 7.5 it is 262144.

But - when add new drive to existing array and partition (or drive) is
smaller than 262144 plus array data (array device size) when mdadm
calculates something between 2048 and 262144. -> so as above magic
cmd's in my case it was 200704 sector.

I recovered it by doing all steps regarding mdadm in virtual
enviroment and I am surprised by the non standard data offsets.

Thanks for Phil

regards
Gerard