Multidata center replication

Another interesting feature provided by Cassandra is the ability to replicate data across multiple data centers or geographical zones in near real-time. This is natively supported by Cassandra and doesn't need to be managed at the application level. Cassandra also provides local consistency levels to ensure cross-region latency doesn't impact client queries. A multiregion cluster can sustain disasters or entire data centers going down. Ideally, there is no need for backups or disaster recovery when running multidata center clusters except for cases of data corruption.

On April 21, 2011, Amazon experienced a large outage in AWS US-East. Some websites were impacted, while others were not. For Netflix, their systems are designed explicitly for these sorts of failures. The SimpleDB, S3, and Cassandra services that Netflix depends upon were not affected by the outage because of the cross-region replication that these services provide.