[stubish]

Yes, you can run multiple nodes on a single physical server. However, then you have the additional headache of ensuring that only one copy of data gets stored on that physical server, or else you can lose your data if that server dies. Similar to having multiple nodes backed by the same storage system, where you need to ensure losing a disk or volume doesn't lose two or more copies of data. Cassandra lets you organize your replicas into 'data centers', and some control inside a DC by allocating nodes to 'racks' (with some major gotchas when resizing, so not recommended!). Translating that into VMs running on physical servers and shared disk is (was?) not documented.