Longhorn isn’t just about replication (which is not backup, and RAID is not backup either). Also if you only have one replica, is it even different from local storage at this point?

You’d use longhorn to make sure applications don’t choke and die when the storage they are using go down. Also, I’m not sure if you can supply longhorn storage to nodes that don’t run it. I haven’t tried it.

I suspect all pods that you’d define to use longhorn would only go up at the longhorn replica node.

All this is how I understand longhorn works. I haven’t tried it this way, my only experience is running it on every node so if one node goes down pods can just restart on any other node and carry on.