Data Replication
Replication strategy is defined per keyspace, and is set during keyspace creation.
Two replication strategies are available:
- SimpleStrategy
- NetworkTopologyStrategy
SimpleStrategy
Use only for a single datacenter and one rack. SimpleStrategy places the first replica on a node determined by the partitioner. Additional replicas are placed on the next nodes clockwise in the ring without considering topology (rack or datacenter location).
NetworkTopologyStrategy
Use NetworkTopologyStrategy when you have (or plan to have) your cluster deployed across multiple datacenters. This strategy specifies how many replicas you want in each datacenter.
NetworkTopologyStrategy attempts to place replicas on distinct racks because nodes in the same rack (or similar physical grouping) often fail at the same time due to power, cooling, or network issues.
When deciding how many replicas to configure in each datacenter, the two primary considerations are (1) being able to satisfy reads locally, without incurring cross data-center latency, and (2) failure scenarios.