Data Recovery from a 4-Disk NAS RAID 10

Question

I know there are similar questions to this but none specific to RAID 10 extracted from a NAS, so any help is greatly appreciated.

So, basically the NAS is kaput but the drives are ok. Following the advice of the Seagate tech who basically said that replacing the NAS would format the drives upon start-up I want to connect the drives to a Linux PC and use MDADM to create a software array and recover the data.

The problem is I have no idea how to use MDADM and influenced from other horror stories I do not want to risk using the wrong command and corrupting the data.

Based on what I have read I should connect the drives via SATA to my linux PC, boot up, open a root terminal and run the following:

mdadm --assemble --scan

And then magically the drive will appear in the file manager and I can just copy the files?

Am I missing something or is this too easy? Also, is the command ok?

Thanks for helping ;)

Answer 1

The horror stories are from people running mdadm --create because they want to “create” a new array using existing array components. What --create does is to create a new, empty array, using existing disks or partitions (and overwriting what they used to contain).

Each volume in an array contains a header which includes UUID of the array as well as information as to where it fits in the array. This allows mdadm to reconstruct arrays simply by presenting their components and letting it sort out which volumes go together and how to use them. The header content is what determines how a volume is used, not how the volume is connected to the computer. If enough volumes are present, you shouldn't need to do anything other than mdadm --assemble --scan.

Running mdadm --assemble without --force won't destroy your data.