Decommissioning Role Instances
You can remove a role instance such as a DataNode from a cluster while the cluster is running by decommissioning the role instance.
When you decommission a role instance, Cloudera Manager performs a procedure so that you can safely retire a host without losing data. Role decommissioning applies to HDFS DataNode, MapReduce TaskTracker, YARN NodeManager, and HBase RegionServer roles.
Hosts with DataNodes and DataNode roles themselves can only be decommissioned if the resulting action leaves enough DataNodes commissioned to maintain the configured HDFS replication factor (by default 3). If you attempt to decommission a DataNode or a host with a DataNode in such situations, the decommission process will not complete and must be aborted.
A role will be decommissioned if its host is decommissioned.
To remove a DataNode from the cluster, you decommission the DataNode role as described here and then perform a few additional steps to remove the role. See the topic Delete a DataNode.
- If you are decommissioning DataNodes, perform the steps in the topic Tuning HDFS Prior to Decommissioning DataNodes.
- Click the service instance that contains the role instance you want to decommission.
- Click the Instances tab.
- Check the checkboxes next to the role instances to decommission.
- Select , and then click Decommission again to start the process.
You can abort the decommission process by clicking the Abort button, but you must recommission and restart the role.
The Commission State facet in the Filters list displays Decommissioning while decommissioning is in progress, and Decommissioned when the decommissioning process has finished. When the process is complete, a is added in front of Decommission Command.