I have two machines, one with mdadm RAID 1 on root partition and one with mdadm RAID 10 on root partition with 4 drives. Ubuntu machines, now I need to upgrade these.
If something goes wrong I need a surefire way to restore original content. What is the proper method for that?
If I save every single drives content with dd then I think it can be restored. But that way I need 2 times more storage then actual content. Is there a better way which is still absolutely fail save?