An additional benefit — besides elasticity and fault tolerance — of having a single type of nodes in your cluster:
Having all nodes share the same role also streamlines operations and systems administrations tasks as well. Because Cassandra has a single node type, it has only a single set of requirements for hardware, for monitoring, and deployment.
As far as I can tell, Cassandra, Riak, Project Voldemort, Membase
, and Terrastore
 are the ones following this philosophy.
Original title and link: Why Every Node in a Cassandra Cluster is the Same (NoSQL databases © myNoSQL)