Cluster Configuration Overview
Cloudera Manager manages the configuration of all roles running in a cluster.
When Cloudera Manager configures a service, it allocates roles that are required for that service to the hosts in your cluster. The role determines which service daemons run on a host.
- One host to run the NameNode role.
- One host to run as the secondary NameNode role.
- One host to run the Balancer role.
- Remaining hosts as to run DataNode roles.
A role group is a set of configuration properties for a role type, as well as a list of role instances associated with that group. Cloudera Manager automatically creates a default role group named Role Type Default Group for each role type.
When you run the installation or upgrade wizard, Cloudera Manager configures the default role groups it adds, and adds any other required role groups for a given role type. For example, a DataNode role on the same host as the NameNode might require a different configuration than DataNode roles running on other hosts. Cloudera Manager creates a separate role group for the DataNode role running on the NameNode host and uses the default configuration for DataNode roles running on other hosts.
Cloudera Manager wizards autoconfigure role group properties based on the resources available on the hosts. For properties that are not dependent on host resources, Cloudera Manager default values typically align with Cloudera Runtime default values for that configuration. Cloudera Manager deviates when the Cloudera Runtime default is not a recommended configuration or when the default values are invalid.