HOWTO: Linux Software Raid using mdadm

[rickyrockrat]

It just sounds like your raid didn't rebuild so it can mount. Is there more of the message? You should see something like can't mount xxx.

If you dump /dev/disk/by-id or /dev/disk/by-uuid like so (xxx replaced by however you want to list):

ls -l /dev/disk/by-xxx

It will give us a better understanding of how your system is configured. Did /etc/fstab change? Is root on md0? If yes, your raid array did not assemble before the attempted mount of root.

[mintfrish]

Ooh thanks so much mate. Sorry I check back in so late.

Unfortunately I already reinstalled ubuntu on my array. To know what caused the problem would be a good thing but now it's too late, isn't it ? Anyways memtest detected problems with RAM memory so it's likely that this was the wrongdoer.

[reko420]

Everything went OK then I rebooted to complete install and I get a grub error

Error file not found

OK just kept trying got it to boot but it only loads the root aray

[Tom_T]

Today my Western Digital NAS drive has failed.

I've removed the single 1TB Disk and connected it via SATA -> USB to my Ubuntu PC.
Nothing is detected.

If I run gparted I get :

/dev/sdb1 - Unknown - 128MiB
unallocated - Unallocated - 931.39 GiB

I've been told :
It's a mdmadm software RAID volume, this is why you can't see your data.

Can any one advise how I get my data back ?

Thanks

[Kissell]

If you had a NAS that had a RAID array configured... why did you remove the drive from it? If a single disk failed, you should still have been able to access all your files on the NAS. If you removed the failed disk and are trying to access files on it, that's not going to work. If you removed the remaining good disk of a mirrored set, you should be able to view those files on a Ubuntu PC, assuming you have mdadm installed and have assembled the degraded array.

apt-get install mdadm

mdadm --assemble --force /dev/md127 /dev/sdb1
NOTE: sdb1 needs replaced with the device letter of the disk you plugged in.

[Tom_T]

Hi
Thanks for taking the time to reply.

I removed the disk as the NAS drive has started flashing the LED's to indicate it couldn't boot.

I'm hoping I'll be able to recover the data.

I don't know if the disk was configured as raid. I was setup as default.
The NAS is a western digital my world book white light, single 1TB SATA disk.
I've not done any thing with it apart from copying data to it.

I've tried the command you've listed and it returns:
mdadm: no recogniseable superblock on /dev/sdb1
mdadm: /dev/sdb1 has no superblock - assembly aborted

Anything else I can try ?

Thanks

[Kissell]

mdadm is a tool for combining multiple disks into a redundant array, so that if a disk fails you can still access all your data.

If you only had one disk in your NAS then it wouldn't have been using mdadm, and you'll have to use some other software to attempt to recover your data from the hard drive. But if the disk is bad that might be impossible. You should restore from your backup =p or take the hard drive to a local PC repair shop that specializes in hard drive data recovery. Sorry, but mdadm and "RAID" don't apply to NAS devices with only one disk.

[Tom_T]

Thanks again for your advise.
Any suggestions on recovering this using Ubuntu?

[Tom_T]

Running Test Disk
Shows this for the drive:


Disk /dev/sdb - 1000 GB / 931 GiB - CHS 121601 255 63
Analyse cylinder 402/121600: 00%


MS Data 64320 3984063 3919744
Linux Raid 64320 3984191 3919872 [md0]
Linux Swap 3984192 4497967 513776
Linux Raid 3984192 4498111 513920 [md1]
MS Data 4498176 6473983 1975808
Linux Raid 4498176 6474111 1975936 [md3]
Linux Raid 6474176 1953524869 1947050694 [MyBookWorld:2]

Doesn't this suggest it's a raid disk ?

Help ! thanks

[rickyrockrat]

It looks like your drive is partitioned as follows:
/dev/sdb1 MS Data (whatever that is - I assume it is a Microsoft something)
/dev/sdb2 is md0, a Linux software raid
/dev/sdb3 is Linux swap (just ignore this)
/dev/sdb4 is md1, the second Linux Software raid
/dev/sdb5 is again Microsoft something
/dev/sdb6 is md3, yet another Linux Software raid.

The last looks like it may be a vendor-specific partition. So use /dev/sdb2, /dev/sdb4, and /dev/sdb6 as input to mdadm.