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Re: recover data from linear raid




As Christian said, specific error message help a lot.
Assume the two devices are hdc and hde,

 fdisk -l /dev/hdc
 fdisk -l /dev/hde
 mdadm -E /dev/hdc
 mdadm -E /dev/hde

and my best guess

  mdadm --build /dev/md0 --level linear --raid-disks 2 /dev/hdc /dev/hde
  fsck -n /dev/md0

(and linux-raid vger kernel org might be a better mailing list for
this particular sort of problem).

Disk /dev/hdb: 250.0 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot    Start       End    Blocks   Id  System
[root node004 root]# fdisk -l /dev/hdc

Disk /dev/hdc: 300.0 GB, 300090728448 bytes
255 heads, 63 sectors/track, 36483 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot    Start       End    Blocks   Id  System
[root node004 root]# mdadm -E /dev/hdb
/dev/hdb:
          Magic : a92b4efc
        Version : 00.90.00
           UUID : 293be3e8:5a7ac6e7:adefc469:84f8aefb
  Creation Time : Fri Jun 23 15:47:10 2006
     Raid Level : linear
    Device Size : 244198464 (232.89 GiB 250.06 GB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 0

    Update Time : Fri Jun 23 15:48:43 2006
          State : clean, no-errors
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0
       Checksum : f790e07f - correct
         Events : 0.2

       Rounding : 32K

      Number   Major   Minor   RaidDevice State
this     0       3       64        0      active sync   /dev/hdb
   0     0       3       64        0      active sync   /dev/hdb
   1     1      22        0        1      active sync   /dev/hdc
[root node004 root]# mdadm -E /dev/hdc
/dev/hdc:
          Magic : a92b4efc
        Version : 00.90.00
           UUID : 293be3e8:5a7ac6e7:adefc469:84f8aefb
  Creation Time : Fri Jun 23 15:47:10 2006
     Raid Level : linear
    Device Size : 244198464 (232.89 GiB 250.06 GB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 0

    Update Time : Fri Jun 23 15:48:43 2006
          State : clean, no-errors
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0
       Checksum : f790e054 - correct
         Events : 0.2

       Rounding : 32K

      Number   Major   Minor   RaidDevice State
this     1      22        0        1      active sync   /dev/hdc
   0     0       3       64        0      active sync   /dev/hdb
   1     1      22        0        1      active sync   /dev/hdc
[root node004 root]# mdadm --build /dev/md0 --level linear --raid-disks 2 /dev/hdb /dev/hdc
mdadm: array /dev/md0 built and started.

fsck -n /dev/md0
fsck 1.32 (09-Nov-2002)
e2fsck 1.32 (09-Nov-2002)
Couldn't find ext2 superblock, trying backup blocks...
fsck.ext2: Bad magic number in super-block while trying to open /dev/md0

The superblock could not be read or does not describe a correct ext2
filesystem.  If the device is valid and it really contains an ext2
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
    e2fsck -b 8193 <device>

fsck -b 8193 /dev/md0
fsck 1.32 (09-Nov-2002)
e2fsck 1.32 (09-Nov-2002)
fsck.ext2: Bad magic number in super-block while trying to open /dev/md0

The superblock could not be read or does not describe a correct ext2
filesystem.  If the device is valid and it really contains an ext2
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
    e2fsck -b 8193 <device>


During a recovery attemp today by mistake I created a mirror array with hdb as the primary and hdc as the secondary. I interrupted the array creation almost immediately, but part of the hdc was overwritten. However the array never held more than 70 gbytes of data, so I hope everything is intact on hdb :/


	Thank you all for your kind help:)
--
============================================================================

Dimitris Zilaskos

Department of Physics @ Aristotle University of Thessaloniki , Greece
PGP key : http://tassadar.physics.auth.gr/~dzila/pgp_public_key.asc
	  http://egnatia.ee.auth.gr/~dzila/pgp_public_key.asc
MD5sum  : de2bd8f73d545f0e4caf3096894ad83f  pgp_public_key.asc
============================================================================


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