I think people over think how hard this actually is. Data replication isn't a new concept. You can use RAID with a NAS or setup async replication with operators for things like Postgres/SQL.

Obviously it's worth doing simulated disaster recovery to ensure you would recover if there is hardware failure. The larger the scale and throughput with parallel writes against the same keys, etc then the more complicated the setup will be. I hope to write more on this topic, but setting up a persistent volume with a NAS is a great way to ensure high durability.

The answer is: it depends. It depends on if you use persistent volumes, and how well is your pv isolated from the failed node. If done right, no data loss.

No, attached storage is not part of the node (not directly). It's something like attaching external (host) directory to a docker container. Your can kill the node/pod and storage is not affected, later you can attach new pod to the same storage.