[jeffbcross]

With MongoDB, there's a concept called Sharding, that divides a collection based on a property in the collection the developer selects.

http://www.mongodb.org/display/DOCS/Sharding+Introduction

Each shard can be either a single node, or can be divided among nodes in a Replica Set for distributed reads.

http://www.mongodb.org/display/DOCS/Replica+Sets