Replication is perhaps the most critical feature of a distributed data store, as it would otherwise be impossible to make any sort of availability guarantee in the face of a node failure. As you learned in Chapter 1, Cassandra's Approach to High Availability, Cassandra employs a sophisticated replication system that allows fine-grained control over replica placement and consistency guarantees.
In this chapter, we'll explore Cassandra's replication mechanism in depth, including the following topics:
The replication factor
How replicas are placed
How Cassandra resolves consistency issues
Maintaining replication factor during node failures
Consistency levels
Choosing the right replication factor and consistency level
At the end of this chapter, you'll be able understand how to configure replication and tune consistency for your specific use cases. You'll be able to intelligently choose options that will provide the fault tolerance and consistency guarantees that are appropriate...