On Thu, 2013-12-05 at 17:00 +0100, Bernd Schubert wrote:

On 12/05/2013 04:48 PM, Wilson Jonathan wrote:

quoted

Still the same problem, lists non partitioned space, unknown, unknown,
un partitioned.

I wonder if the problem is because i'm not re-creating it with bitmap
file, which is listed as starting 8 sectors from superblock, so with it
not being there the partition table is being read from this space and
not further along the space.

The bitmap is supposed to be in the gap between data and superblock.

quoted

Infact, looking at the re-created superblock there is a change...

/dev/sde6:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x0
      Array UUID : 1c413162:25c7b4af:7b305603:1ce49fed
            Name : BorgCUBE:5  (local to host BorgCUBE)
   Creation Time : Thu Dec  5 00:28:11 2013
      Raid Level : raid6
    Raid Devices : 6

  Avail Dev Size : 1833309583 (874.19 GiB 938.65 GB)
      Array Size : 3666617344 (3496.76 GiB 3754.62 GB)
   Used Dev Size : 1833308672 (874.19 GiB 938.65 GB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
           State : clean
     Device UUID : de841586:f82b22ed:1a234ae7:57fbb36a

     Update Time : Thu Dec  5 00:28:11 2013
        Checksum : 9dcbeec1 - correct
          Events : 0

          Layout : left-symmetric
      Chunk Size : 64K

The "data offset" is 262144 where as the sdc (original) is 2048

Seems to be a new mdadm version with different default values. Another 
reason not to use '--create' unless there is really no other way. Try to 
add --data-offset=1M.

My version of mdadm does not have --data-offset...

root@BorgCUBE:/mnt/datastore/wilsonjonathan# mdadm --create
--assume-clean --level=6 --raid-devices=6 --chunk=64
--data-offset=1M /dev/md5 /dev/sdd6 /dev/sde6 /dev/sdf6 /dev/sda6
missing missing 
mdadm: unrecognized option '--data-offset=1M'

I also double checked the original, pre-corrupted, examine and found
that /dev/sdb6 had 1928 sectors (was a new 3tb drive, using a partition
on it, which had a slightly larger size, to replace the original
partition on a 1tb disk)

sda6:3, sdd6:0, sde6:1, sdf6:2 are all at 2048 sectors, so if I can
somehow create md5 using just these 4 disks it should be ok even if it
has no redundancy, assuming it works and I can get hold of a mdadm with
offset (I have git, and have built from source before if it comes to
that... but a binary would be more helpful, or perhaps a mdadm that had
the original 2048 offset?) then clear the superblock from b and c and
re-add them to re-build the redundancy.

Thanks.

Cheers,
Bernd


PS: Btw, for assemble the order of devices doesn't matter, the kernel 
know the correct order from their superblocks...