Apache Cassandra™ 2.0

Snitches

A snitch determines which data centers and racks are written to and read from.

Snitches inform Cassandra about the network topology so that requests are routed efficiently and allows Cassandra to distribute replicas by grouping machines into data centers and racks. All nodes must have exactly the same snitch configuration. Cassandra does its best not to have more than one replica on the same rack (which is not necessarily a physical location).

Note: If you change the snitch after data is inserted into the cluster, you must run a full repair, since the snitch affects where replicas are placed.
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