Ext3 users - Jun 2006 - recover data from linear raid

Hello,

 	I had a scientific linux 3.0.4 system (rhel compatible), with 3 
ide disks, one for / and two others in linear raid (250 gb and 300 gb 
each).
 	This system was obsoleted so i move the raid disks to a new 
scientific linux 3.0.7 installation. However, the raid array was not 
detected ( I put the disks on the same channels and same master/lsave 
setup as in the previous setup). In fact fdisk reports that the disks are 
not partitioned.
 	I had around 70 gb data on that array I would like to recover. I 
used dd on the disks  and strings on the resulting file. The data is there 
but fsck complains about superblocks and fails.

 	Recommentations on how to proceed are greatly appreciated.

 	Best regards,





--
===========================================================================
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
============================================================================

On Sat, 24 Jun 2006, Dimitris Zilaskos wrote:
> scientific linux 3.0.7 installation. However, the raid array was not
detected
> ( I put the disks on the same channels and same master/lsave setup as in
the
well, first of all: you have to make sure that your raid array is set up 
correctly. no fs-magic can help here if the underlying blockdevice has 
been mangled.
> previous setup). In fact fdisk reports that the disks are not
> partitioned.
perhaps the raid-array has been created from disks, not from partitions?
e.g.
   - /dev/md0 out of /dev/sda, /dev/sdb, /dev/sdc
      instead of
   - /dev/md0 out of /dev/sda1, /dev/sdb1, /dev/sdc2
> dd on the disks  and strings on the resulting file. The data is there but 
> fsck complains about superblocks and fails.
please provide errorlogs, fsck's, fdisk's output of what you did...

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On Saturday June 24, dzila at tassadar.physics.auth.gr
wrote:
> 
>  	Hello,
> 
>  	I had a scientific linux 3.0.4 system (rhel compatible), with 3 
> ide disks, one for / and two others in linear raid (250 gb and 300 gb 
> each).
>  	This system was obsoleted so i move the raid disks to a new 
> scientific linux 3.0.7 installation. However, the raid array was not 
> detected ( I put the disks on the same channels and same master/lsave 
> setup as in the previous setup). In fact fdisk reports that the disks are 
> not partitioned.
>  	I had around 70 gb data on that array I would like to recover. I 
> used dd on the disks  and strings on the resulting file. The data is there 
> but fsck complains about superblocks and fails.
> 
>  	Recommentations on how to proceed are greatly appreciated.
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 at vger.kernel.org might be a better mailing list for
this particular sort of problem).

NeilBrown

>
> 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 at 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 at 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 at 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 at 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 at 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
============================================================================