Partition gone after RAID5 recreate

How to use TestDisk to recover lost partition
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passzschu
Posts: 5
Joined: 03 Dec 2014, 07:28

Partition gone after RAID5 recreate

#1 Post by passzschu » 03 Dec 2014, 07:48

I had to recreate my RAID5 but now I can't find any partitions on it.

Scanning only the first drive the partition is still there with the correct informations.

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Raid magic value at 0/0/9
Raid apparent size: 3303457500 sectors
     Linux md 1.x RAID        0   0  1 121584 248 16 1953262600 [nasbox:127]
     md 1.x Raid 5 - Array Slot : 0 (0, 1, 2), 1000 GB / 931 GiB
     ext4                     0  32 33 364803 157 26 5860568064 [part]
     EXT4 Large file Sparse superblock Recover, 3000 GB / 2794 GiB
This partition ends after the disk limits.
recover_EXT2: part_offset problem
recover_EXT2: part_offset problem
recover_EXT2: part_offset problem
recover_EXT2: part_offset problem
recover_EXT2: part_offset problem
Search for partition aborted
Disk /dev/sdb - 1000 GB / 931 GiB - CHS 121601 255 63
Check the harddisk size: HD jumpers settings, BIOS detection...
The harddisk (1000 GB / 931 GiB) seems too small! (< 3000 GB / 2794 GiB)
The following partition can't be recovered:
     ext4                     0  32 33 364803 157 26 5860568064 [https://sd2dav.1]
     EXT4 Large file Sparse superblock Recover, 3000 GB / 2794 GiB
How can I recover this partition on the RAID?

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

Re: Partition gone after RAID5 recreate

#2 Post by Fiona » 03 Dec 2014, 08:47

I had to recreate my RAID5 but now I can't find any partitions on it.
Would it be possible that your recognized array is too small?
The size of your array (RAID5-Disk) is 1 TB only instead of 3 TB partition size?

Fiona

passzschu
Posts: 5
Joined: 03 Dec 2014, 07:28

Re: Partition gone after RAID5 recreate

#3 Post by passzschu » 03 Dec 2014, 08:58

No, the RAID5 consist of 4 disks each 1TB, that result in 3TB RAID filesystem size.
The output was from scanning the first disk. When I scan the whole RAID nothing is found.

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

Re: Partition gone after RAID5 recreate

#4 Post by Fiona » 03 Dec 2014, 11:18

I had to recreate my RAID5 but now I can't find any partitions on it.
Your size of your Disk is 1 TB:
Disk /dev/sdb - 1000 GB / 931 GiB - CHS 121601 255 63
It's not possible to recover a 3 TB partition on an 1TB disk.
Can you check it?
4x 1TB Array results in 3 TB size, because the size of 1 disk is reserved for parity.
Currently I only see a 1 TB Disk or array in testdisk but it should be 3 TB?
I assume that something is wrong with your disk, array or RAID5?

Fiona

passzschu
Posts: 5
Joined: 03 Dec 2014, 07:28

Re: Partition gone after RAID5 recreate

#5 Post by passzschu » 03 Dec 2014, 11:35

I know this, my question was why the partition is not found at the raid device, only on the single disk.
In my opinion the raid is exactly created as before.
I can see the data is still there but obviously can't be read on the assembled raid device.

Is it possible to guess from the ext4 definition on the single disks in which order the disk should be assembled?

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

Re: Partition gone after RAID5 recreate

#6 Post by Fiona » 03 Dec 2014, 12:25

Your partition would be found on your RAID if you recreated your RAID exactly like before.
Your disks must be in sequential order, exactly like before.
Normally you can use datarecovery software and scan your file system to have a try to recover some files.
If your files are intact, your recreated array might be ok.
If you're unsure, I've seen some users, which used a trial of commercial datarecovery software with virtual RAID5 support to check their array.

Fiona

passzschu
Posts: 5
Joined: 03 Dec 2014, 07:28

Re: Partition gone after RAID5 recreate

#7 Post by passzschu » 03 Dec 2014, 12:48

Can you give me some names of commercial software for linux?

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