Cannot mount RAID-1 hard drive

[Lonni J Friedman]

On Wed, Nov 28, 2012 at 8:09 AM, CHONG Yu Meng <chongym at cymulacrum.net> wrote:
>> From: "Lonni J Friedman" <netllama at gmail.com>
>>
>> With Linux mdraid, there are two components. You have the ondisk
>> format for the array, and then you have the state of the array (in
>> /proc/mdstat ). What seems wrong/broken in your setup is that the
>> partition type should be id=fd (Linux raid), and not type=83.
>> However, the fact that the array was seemingly started (and visible in
>> /proc/mdstat ) suggests that the array is fine, but the discrepancy
>> between the partition type & filesystem information is causing
>> confusion. You might try changing the partition type to fd, and see
>> if you can then mount it.
>>
>> Also you never said, which Linux distribution was managing this RAID
>> array prior to the disk failure? Its possible, although unlikely that
>> something in that SUSE Live CD is either broken or incompatible with
>> whatever is on disk.
>
>
> Thanks, Lonni!
>
> How would I go about changing the partition type and would I run the
> risk of losing data if I did so? I'm not familiar with this, so
> command-line examples would be much appreciated! :)

Changing a partition type should not normally have any impact on the
data inside the partition.  You can do so with fdisk (likely parted
too, but I'm not as familiar with it).  Something like:
fdisk /dev/sdb

then type 't', enter the partition number (2 in this case?), and
finally enter fd, save & quit.

>
> So, I change the partition type to fd then start the array, then
> mount the array? i.e. mount /dev/md127?

That should work.

>
> The hard disks come from a DLink DNS-323, so my guess is the
> distribution they are running is probably Debian. The Live CD
> I am using to mount the hard disk is OpenSUSE 12.2 (Gnome). I
> don't know if there are issues with parted in OpenSUSE though.
>
> The trouble is, I cannot bring the hard disks out of the customer
> site, so I have to do the data extraction there. I could try
> with a Fedora Live CD and see if the results are different, though.

That might be a good test if you're still having problems with the SUSE CD.

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
L. Friedman                                    netllama at gmail.com
LlamaLand                       https://netllama.linux-sxs.org