Why use the Backup Service? 

The Backup Service provides backup and recovery for an enterprise's data even though DataStax Enterprise has built-in replication.

The Backup Service was designed to manage enterprise-wide backup and restore operations for DataStax Enterprise clusters. While some administrators and operations staff believe that backup is not needed because of powerful and flexible replication capabilities in Cassandra, proper backup and restore procedures are still very important to implement for production clusters.

While replication in Cassandra does provide for copies of data to exist in multiple locations, datacenters, and cloud availability zones, all operations performed in a cluster are replicated, including operations that result in lost or incorrect data. For example, if a table is mistakenly dropped, if data is accidentally deleted, or if the cluster's data is corrupted, those adverse events will be replicated to all other copies of that data. In such cases, there is no way to recover the lost or uncorrupted data without a backup of the data. The Backup Service provides a simple interface for scheduling regular or one-off backups of all or specific keyspaces in a cluster, and for recovering data from the stored backups.

DataStax strongly recommends that organizations using DataStax Enterprise create a good backup and recovery plan using the Backup Service. Testing backup and restore operations on a non-production cluster is also recommended so you can ensure that the disaster recovery plan you deploy actually works as you intend.