[GTALUG] Raid 10 repair question

[Digimer]

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First, you should have backups. Why not get an external USB drive? You
can get those quite inexpensive. Heck, even a 64GB thumb drive
shouldn't be too expensive, though flash is not the most reliable.

No matter what, I would start with a good backup. Playing with mdadm
is relatively safe, but if it's your first time playing with it, you
can get yourself into trouble.

Hardware RAID controllers often auto-use replacement drives to rebuild
a degraded array, but mdadm does not. How exactly you go about
repairing the array depends on your specific configuration and which
drive failed. You will need to start by partitioning the replacement
drive such that it matches the existing drives (each array has to have
a partition equal to or larger than the same partitions on the other
drives).

Once partitioned (and rebooted, if needed), you will add the new
partition to the degraded array. Once added, mdadm will start
re-assembling the array. Note that if one of the arrays has /boot,
you'll probably need to run grub's install on the raw disk so that it
can be booted from.

The command to add the new partition to an existing array will look
something like this:

mdadm --manage /dev/md0 --add /dev/sda1

Obviously, the 'mdX' and 'sdYZ' will need to be adjusted for your
configuration.

digimer

On 17/02/15 04:42 PM, o1bigtenor wrote:
> Greetings
> 
> I have been running a raid 10 array for almost 3 years.
> 
> Last September on a reboot (forced by Firefox and kernel memory 
> interaction problems) came up with one of the drives being listed
> as DOA. The raid array has continued to run on 3 drives although on
> reboots there is much complaining from whatever in the boot up
> process. I had the replacement drive sent to me and today I
> installed the drive.
> 
> I was under the assumption that the raid array would rebuild itself
> upon startup with a new drive (4th out of 4).
> 
> This did not happen.
> 
> I am running Debian Jessie (testing) and have the whole time in
> question. I can mount the array and it is visible. I'm looking at
> backing up the array (on blu-ray discs) but as I'm now to circa 45
> GB of data and I was at about 22 GB when I last did a backup this
> is going to be a momentous event.
> 
> How do I ask mdadm to include this new drive into the array?
> (Without borking everything!! I have found lots of instructions on
> how to create but none in an hour of trying different search
> phrases on how to rebuild or how to cause the array to rebuild
> itself. I have only been able to find instructions for when the
> array is totally sick and I'm not there (yet - - - grin!) but I
> don't want to wait until another drive craps out to get things
> going.)
> 
> TIA
> 
> Dee
> 
> 
> --- Talk Mailing List talk at gtalug.org 
> http://gtalug.org/mailman/listinfo/talk
> 


- -- 
Digimer
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