The model of data distribution we have developed thus far is, in fact, a simplification of how a modern Cassandra cluster works. While versions of Cassandra prior to 1.2 did directly map ranges of tokens onto physical nodes, Cassandra 1.2 introduced virtual nodes, which act as an intermediary in the mapping process.
Virtual nodes replace physical nodes in the partitioned ring; each virtual node owns a portion of the token space. Virtual nodes themselves are then owned by physical nodes, but a physical node does not own a contiguous range of virtual nodes; rather, virtual nodes are distributed randomly among physical nodes. Crucially, there are many more virtual nodes than physical nodes; each physical machine is responsible ...
