No they can't. This probably needs to be better documented, but the storage directory has to be totally unique for a server. If you run a cluster on one machine and all the nodes use the same folder, what will happen is they'll just start using each other's state and you'll see some strange behavior. When the first node starts it will be fine, but when the second node starts it will think it's recovering from disk and use the first node's configuration. So, if you did that with two separate clusters, they'd probably just end up getting merged into one since the nodes rely on the configuration in that folder to know where their peers are.