Recover partition from defective RAID-10 array

How to use TestDisk to recover lost partition
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rabeno
Posts: 2
Joined: 27 May 2012, 09:46

Recover partition from defective RAID-10 array

#1 Post by rabeno » 22 Jun 2012, 13:48

Hi all,

Well, I have a Seagate NAS-440 with 4x2TB disks arranged in RAID-10, making a total of 4TB drive. The problem is that afew months ago my 3rd drive went to HD heaven... simply dead - physical damage. It's still "readable" to some extent, but I can not re-join it to the array to get the data.
To make an even more interesting story (or just my bad luck..) my 4th drive probably missed his partner and after a few days (I havn't got the chance to get another drive to replace the 3rd one yet). The 4th drive is fully readable, but is marked as dirty so I can not re-join it to the array. Further more, my NAS decided that there was a FW update and went ahead to download it... of course it did... the FW image extracted to my 4th drive as well, "running over" the partition structure it was in the last state.
Now for the crucial part... both drives were apperently a couple (RAID-1) so it is kind of good thing, because I can get the data from the 4th drive, and a bad thing because I have to recover the partitions first to be able to re-join it to the array and input a freshly bought drive instead of my 3rd one to rebuild the entire array.

I have connected the 3rd and 4th drives to my pc (running WinXP and TestDisk 6.14) and have scanned them for a partition list (list of both drives attached)

After reading many of the questions here I went ahead and tried getting an image of my 3rd drive. It took about one week, countless errors of CRC (again, physical damage) and finally I got myself a nice, cool, 400MB image.dd file. I tried opening it with TestDisk, as described in the FAQ, and scanned it. It found the [DATAVOLUME] partition that I need, but says it cannot be recovered because the disk size is too small.

So, now I have the image.dd from the 3rd drive and my 4th drive, also with the [DATAVOLUME] partition hiding and cannot be recovered.

Any help would be appreciated
Michael
Attachments
disk_part_4.jpg
Partition list after scan of the 4th drive
disk_part_4.jpg (58.02 KiB) Viewed 1067 times
disk_part_3.jpg
Partition list for the 3rd drive
disk_part_3.jpg (48.57 KiB) Viewed 1067 times

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Fiona
Posts: 2836
Joined: 18 Feb 2012, 17:19
Location: Ludwigsburg/Stuttgart - Germany

Re: Recover partition from defective RAID-10 array

#2 Post by Fiona » 25 Jun 2012, 07:16

I have connected the 3rd and 4th drives to my pc (running WinXP and TestDisk 6.14) and have scanned them for a partition list (list of both drives attached)
For a successful recovery you need a 4 TB array (RAID0)!
Both must be your striped disks.
Doesn't a matter from RAID 0 or Mirror and they must be in sequential order.
Reason is, your data are written in blocks or stripes to each disk(stripe size is often 64 KB.
You'll get the values from your BIOS of your RAID controller.
but is marked as dirty so I can not re-join it to the array.
Does your RAID controller complain?
If windows want to check it you can use chkntfs.
http://support.microsoft.com/kb/160963/en-us

Fiona

rabeno
Posts: 2
Joined: 27 May 2012, 09:46

Re: Recover partition from defective RAID-10 array

#3 Post by rabeno » 30 Jun 2012, 18:22

Hi Fiona. Thank you for your answer.

If I understood correctly I should build a new RAID-0 array on my computer consisting the 2nd and 3rd drive?
Wouldn't it make things worse for a good recovery?
I have 6 new 2TB drives to play with. I can create a 4TB RAID-0 array using those for a recovery. would it be of any help?

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