For mdadm, it stores the metadata on the drives themselves. As long as your is is separate, yes, it should be just fine and detect automatically. After install it should just be a mdadm –assemble –scan and off to the races.

That said, I will always recommend backups. You never know what will happen.

In terms of docker, yes you can back things up and move them over. That said I recommend having your docker contents that need to be persistent as part of a mount somewhere, so that instead of needing to copy them around, you just have a compose that points to a mount.

Makes backups easier too.