Configuring the replication factor

Ensure reliability and fault tolerance by controlling how many data replicas you want to store across a Cassandra cluster.

The replication factor is the total number of replicas for a keyspace across a Cassandra cluster. A replication factor of 3 means that there are three copies of each row, where each copy is on a different node and is equally important.

By setting a high replication factor, you ensure a higher likelihood that the data on the node exists on another node, in case of a failure. The disadvantage of a high replication factor is that write operations take longer.

Before you begin: Determine the optimal replication factor setting that prevents data loss in case multiple nodes in the Cassandra cluster fail. For more information, see Impact of failing nodes on system stability.

Procedure

To change the default replication factor, open the prconfig.xml file and modify the dnode/default_keyspaces property.

The default setting for all keyspaces is 3:

data=3,vbd=3,states=3,aggregation=3,adm=3,adm_commitlog=3