Cloudera Manager uses roles to define the configuration of different hosts in a cluster. Each role will have a certain set of properties and configurations defined that can be applied to a node in the cluster. The role applied to a node will define the different Hadoop services that will run on that specific node.
The following is the list of a few roles applied to a host by Cloudera Manager:
Balancer: This role is responsible for balancing the blocks across the different nodes on the cluster
DataNode: This role defines all the configurations required to start a datanode on the host
NameNode: This role defines all the configurations required to start a namenode on the host
SecondaryNameNode: This role defines all the configurations required to start a secondary namenode on the host
JobTracker: This role defines all the configurations required to start a jobtracker on the host
TaskTracker: This role defines all the configurations required to start a tasktracker...