Multiple Drive failure - Recovery from single clone


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Hey guys,

 

I had the unthinkable happen recently and had 2 drives fail due to an electrical surge. Unfortunately I only have a single parity drive (+4 storage drives).

 

I have sent the drives to a data recovery centre and they are able to recover one of the drives, the other drive is unfortunately not able to be recovered. They have said that it is possible to do a block level clone of the "good" drive onto a new drive. 

 

Would it be possible to use this cloned drive back in the array to emulate/rebuild the drive that they cannot fix?

 

Essentially I would need to update the unraid config to think that the new drive is the old drive. If this is possible how can I do it?

 

Thanks.

 

 

Edited by Pumped
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15 minutes ago, Pumped said:

Disk 3 is the drive that can't be fixed

Assuming disk2 is the one missing, when you get the cloned disk4 do this:

 

-Tools -> New Config -> Retain current configuration: All -> Apply
-Assign any missing disk(s) including cloned disk4 and a new disk2
-Important - After checking the assignments leave the browser on that page, the "Main" page.

-Open an SSH session/use the console and type (don't copy/paste directly from the forum, as sometimes it can insert extra characters):

mdcmd set invalidslot 2 29

-Back on the GUI and without refreshing the page, just start the array, do not check the "parity is already valid" box, disk2 will start rebuilding, disk should mount immediately but if it's unmountable don't format, wait for the rebuild to finish and then run a filesystem check

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Ok got the drives back today. I have done the disk assignments and double checked them.

 

I see this message near my parity drive 'All existing data on this device will be OVERWRITTEN when array is Started'

 

And Starting the array without "parity is already valid" presents the warning "Parity disk(s) content will be overwritten"

Is this correct? If I am to recover the content of disk 2 don't I require the parity to remain in tact? I haven't proceeded past this dialog yet.

Edited by Pumped
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3 minutes ago, Pumped said:

Is this an issue?

Yes, it means it's not a 100% clone of the original, but it might still be possible to access it later.

 

Disk2 being unmountable is also not a good sign, but wait for the rebuild to finish, you can grab and post current diags so we can see why disk2 isn't mounting.

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There is a xfs filesystem on disk2, that's good, if everything else is well it should be fixable when the rebuild finishes, as for disk4 maybe they only cloned the partition, not the mbr, and that would cause that error, but if it's only that it's easily fixable.

 

For now wait for the rebuild finish and then check filesystem on disk2.

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I had the data recovery place give me a copy of the available data on a secondary drive so I have already been able to retrieve the disk4 data. Hoping the clone will help repair disk2.

 

Waiting patiently for the rebuild (~20 hours remaining). Either way, very much appreciate your help @johnnie.black. You're a legend.

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Ok, good news. Rebuild completed overnight and was sucessful. Everything is green.

 

I ran xfs_repair -v /dev/md2 -L on disk2 and the disk mounted   🙌

I can also see all the data correctly on disk 2 so it looks like it worked.

 

Running the same filesystem check on disk 4 did not yield any changes and I am still seeing the "Unmountable: Unsupported partition layout"

 

tower-diagnostics-20190401-1329.zip

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10 hours ago, Pumped said:

Running the same filesystem check on disk 4 did not yield any changes and I am still seeing the "Unmountable: Unsupported partition layout"

That's expected, if it's just a partition problem rebuilding the disk will correct that, and since you already have the data from disk4 no risk anyway:

stop array

unassign disk 4

start array

check if the emulated disk mounts, if yes rebuild on top, if not run a filesystem check on it.

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