# Step 8: Restart HDFS datanodes after adding volumes

After you have configured HDFS data nodes to use Pentaho Data Optimizer volumes, you need to perform additional steps so Ambari operates properly.

Ambari cannot detect the components that are impacted by a configuration change. In addition, it does not support refreshing configurations on a running service instance. Therefore, Ambari prompts you to restart all HDFS components, even though only the data node component is impacted, and the changed property is classified as a “refreshable” property.

Use the **Restart data nodes** method to trigger the data nodes to detect the configuration change. Restarting data nodes is performed entirely in the user interface, but the data nodes restart in a rolling fashion.

As a best practice, restart only data node components in a rolling restart fashion to minimize disruption and to avoid data availability issues. This process does not resolve the notifications in the Ambari UI indicating that all HDFS services need to be restarted.


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