[Sussex] Retrieving data from mirrored disks

[Desmond Armstrong]

On 29/12/13 11:46, Dave Garry wrote:
>
> Hi Fay,
>
> If the disks were using Linux soft RAID (mdadm) then this site should 
> be helpful:
>
> https://raid.wiki.kernel.org/index.php/Linux_Raid
>
> First you need to identify which of two of the three disks were being 
> used as the
> RAID mirrors. Booting a live disk with one disk in a caddy is the way 
> to start.
>
> The output from "fdisk -l" should be all you need to identify the 
> disks - look at the
> "partition type" field - those that are "0xfd" are software RAID.
>
> Commands such as "mdadm --assemble --scan" will probe the disk for RAID
> volumes, these will then be accessible via /dev/mdxx where xx will be 
> unique for
> each volume. You cannot / should not mount the volume via /dev/sdxx, 
> always
> use the /dev/mdxx device as found by mdadm.
>
> The command "cat /proc/mdstat" will show stats on each RAID volume.
>
> When only using one disk from a mirrored pair the volumes will be in 
> degraded
> mode - "cat /proc/mdstat" will show this. You should be able to mount 
> the volumes
> read-only to get to your data...
>
> If hardware RAID was being used then the above may not be of use, and you
> may need another motherboard with the same RAID chipset to be able to 
> read
> them.
>
> I hope this helps.
>
> Regards.
>
> -- 
> Dave Garry
>
> On 29/12/13 04:53, Fay Zee wrote:
>> Hi, Can anyone advise me how to retrieve data from a mirrored disk, 
>> please?
>>
>> I tried putting each disk into an external HDD caddy on two other 
>> Linux machines but could not read them, and did not get any 
>> meaningful information when running a live gparted disk.
>>
>> The mirrored disks are 500GB SATA but there is also an additional 
>> 500GB SATA disk in the machine, which I wasn't using. I don't know 
>> which two are the mirrors.
>>
>> My (desktop) motherboard has developed a fault. The machine boots up 
>> and the disks spin, and there are beeps which we've compared to the 
>> manual, but I am not getting graphics. There are no graphics with a 
>> live CD or DVD either.
>>
>> Ten minutes and two start-ups prior to this fault, the boot up 
>> message reported that it started up with only one of the mirrored disks.
>>
>> The operating system is Debian Squeeze, installed in mirror mode.
>>
>> The motherboard actually supports mirroring but I believe the 
>> mirroring is entirely software driven.
>>
>> I had intended to upgrade to Debian Wheezy at the beginning of 
>> December, so skipped a back-up.
>>
>> I had a friend round who repairs hardware for a living. We tried 
>> removing the battery, shorting out the bios, swapping out the 
>> monitor, the graphics card, the power unit and took out the memory 
>> sticks in turn, as well as testing all the connections.
>>
>> It is a Gigabyte GA M720 US3 nVidia chipset dual bios with extra 
>> thick copper.
>> The processor is AMD Phenom II AM2+ quad core 940.
>> The graphics card is 512MB DDR3 nVidia Geforce 9600GT PCI express - 
>> there is no onboard graphics.
>> There are four 2GB dual channel DDR2 800 PC2 6400 RAM memory sticks.
>>
>> The machine was built for me in 2009.
>>
>>
>> Best regards,
>> Fay

Surely if all you wish to do is to access data then something like Puppy 
Linux should be capable enough?