Apart from Cloudera Data Platorm (CDP) Data Center cluster, there are two types of classic clusters that are used in Replication Manager service, namely Cloudera Distribution of Hadoop (CDH) and Hortonworks Data Platform (HDP).
These clusters are primarily on-premises version of Cloudera Data Platform and they must be registered on the Management Console before they can be used for data migration purposes. CDH on-premise cluster must be managed by Cloudera Manager and enabled for Replication Manager through Cloudera Data Platform. Any HDP on-premise cluster must be managed by Apache Ambari and enabled for Replication Manager through Cloudera Data Platform. For more information, see Managing Classic Clusters.