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Old 06-06-2012, 03:39 AM   #1
Speeko
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Recovering data from a busted RAID5 array


Hi all,

I have been using a 4-disk RAID5 array using an Acer EasyStore NAS.
As was inevitable - the device has failed and no longer recognizes the Array.

I am Now attempting to back up the data from these drives.

So far I have:
Connected 3x of the 4 drives to SATA ports 0-3 on my motherboard.
Booted a Knoppix LiveCD (latest version at time of this writing)
Been able to see the drives in the file explorer as sda4, sdb4, sdc4

Google tells me I need to somehow restore the array using the MDADM command. But I have not been able to figure out the exact commands.

Can anyone help? I am a complete newbie when it comes to Linux.

Thanks
Brett
 
Old 06-06-2012, 04:46 AM   #2
lithos
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Hi,

I don't know exactly, but take a look here if it will help you out.

good luck
 
Old 06-06-2012, 04:51 AM   #3
Speeko
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Quote:
Originally Posted by lithos View Post
Hi,

I don't know exactly, but take a look here if it will help you out.

good luck
Thanks for that. Unfortunately that article covers RAID1 which seems to be far simpler than RAID5.
For some more information, see the results of fdisk -l:

Code:
root@Microknoppix:/home/knoppix# fdisk -l

Disk /dev/sda: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1          66      530113+  82  Linux swap / Solaris
/dev/sda2             198      121471   974133405   83  Linux
/dev/sda4              67         197     1052257+  83  Linux

Partition table entries are not in disk order

Disk /dev/sdc: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1               1          66      530113+  82  Linux swap / Solaris
/dev/sdc2             198      121471   974133405   83  Linux
/dev/sdc4              67         197     1052257+  83  Linux

Partition table entries are not in disk order

Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1          66      530113+  82  Linux swap / Solaris
/dev/sdb2             198      121471   974133405   83  Linux
/dev/sdb4              67         197     1052257+  83  Linux

Partition table entries are not in disk order

Disk /dev/sdd: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdd1               1          66      530113+  82  Linux swap / Solaris
/dev/sdd2             198      121471   974133405   83  Linux
/dev/sdd4              67         197     1052257+  83  Linux

Partition table entries are not in disk order
Here is the command I am currently attempting:

Code:
root@Microknoppix:/home/knoppix# mdadm --assemble /dev/md0 /dev/sd[abcd]2
mdadm: /dev/md0 assembled from 3 drives - not enough to start the array while not clean - consider --force.
I'm not sure if it's right, therefore i am reluctant to re-run with --force.
 
Old 06-06-2012, 10:01 AM   #4
lithos
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Recreate soft-raid array in linux

Can you try it like this auto detect devices?

There is really not much about recovering soft-raid on linux on internet and I don't have any idea whatsoever with it, sorry.


Can anyone here at LQ please help out.

wish you good luck
 
Old 06-06-2012, 01:55 PM   #5
suicidaleggroll
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When you say the "device" has failed, are you referring to the Acer NAS?
You may be able to RMA the NAS, and just put the drives in. It depends on how the NAS stores the array information...on most hardware RAID cards the array information is stored on the disks themselves, so you can swap out the controller and the array stays in-tact. Software RAIDs are a bit harder to recover in the event of a failure...unfortunately I don't have any experience with that (most of my systems are hardware RAID).
 
Old 06-08-2012, 03:31 AM   #6
Speeko
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Got it working!

Was just a matter of running the command from earlier with --force.

Backing up to USB drive now.

Thanks for the help!
 
Old 06-08-2012, 05:12 AM   #7
lithos
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Great,
thanks for reporting back for future references that others may find this.
 
  


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