http://en.wikipedia.org/wiki/Consistent_hashing

A hash scheme that does not affects the entire hash table when a node is inserted or deleted. Machines are assigned to the circular nodes, and if a machine crashes, the keys in the crashed machine are moved to the following node in the circle. This is becoming really popular due to no SQL movements.

Used by distributed hash table (This is basically consistent hashing + node lookup algorithm) or amazon dynamo.