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Speeko 06-06-2012 02:39 AM

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

lithos 06-06-2012 03:46 AM

Hi,

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

good luck

Speeko 06-06-2012 03:51 AM

Quote:

Originally Posted by lithos (Post 4696659)
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.

lithos 06-06-2012 09:01 AM

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

suicidaleggroll 06-06-2012 12:55 PM

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).

Speeko 06-08-2012 02:31 AM

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!

lithos 06-08-2012 04:12 AM

Great,
thanks for reporting back for future references that others may find this.


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