Enabling incremental backups 

Steps to enable incremental backups. When incremental backups are enabled, Cassandra hard-links each memtable flushed to an SSTable to a backups directory under the keyspace data directory.

When incremental backups are enabled (disabled by default), Cassandra hard-links each memtable-flushed SSTable to a backups directory under the keyspace data directory. This allows storing backups offsite without transferring entire snapshots. Also, incremental backups combined with snapshots to provide a dependable, up-to-date backup mechanism. Compacted SSTables will not create hard links in /backups because these SSTables do not contain any data that has not already been linked.A snapshot at a point in time, plus all incremental backups and commit logs since that time form a compete backup.

As with snapshots, Cassandra does not automatically clear incremental backup files. DataStax recommends setting up a process to clear incremental backup hard-links each time a new snapshot is created.

The location of the cassandra.yaml file depends on the type of installation:
DataStax Enterprise 5.0 Installer-Services and package installations /etc/dse/cassandra/cassandra.yaml
DataStax Enterprise 5.0 Installer-No Services and tarball installations install_location/resources/cassandra/conf/cassandra.yaml
Cassandra package installations /etc/cassandra/cassandra.yaml
Cassandra tarball installations install_location/resources/cassandra/conf/cassandra.yaml

Procedure

Edit the cassandra.yaml configuration file on each node in the cluster and change the value of incremental_backups to true.