The DDS service runs on DDS nodes (nodes to which you assigned the DDS node type). A DDS node is a Pega Platform system with an embedded Cassandra database process. DDS nodes constitute a Cassandra cluster that is capable of storing large volumes of data at high speed.
DDS nodes gather data from decision management services and then make that data available for other services to use.
The DDS service distributes decision management data evenly across all DDS nodes. As a result, you can expect approximately the same increase in disk space usage at the same rate.