Mnesia is Erlang's built-in distributed database. It provides primitives for adding nodes to the database set and to manage fragments, but does not prescribe any high-level strategies.

Fragmentron provides one strategy for automatically distributing data as nodes are added and removed from the system. This simplifies Mnesia administration in a dynamic environment, e.g., EC2.

gen_herd is a generalization of the fragmentron strategy to arbitrary Erlang processes, intended for partitioned services that need to be automatically (re)distributed across a computing cluster.

Another Dukes of Erl release.