Which Servers Can I Leave Running When I Add a Machine?

It is best to stop all SAS LASR Analytic Server instances and SAS High-Performance Deployment of Hadoop. For SAS Visual Analytics deployments, stop the SAS LASR Analytic Server Monitor, too.
If you prefer to deny access to the environment while performing this procedure, you can use the SAS High-Performance Computing Management Console to perform an SSH lockout. Be sure to permit access for root, the SAS installer account, the account that is used to run HDFS, and at least one administrator that can start and stop server instances.
You can ensure that saving files to HDFS is denied by using safe mode. The following command is an example:
$HADOOP_HOME/bin/hdfs dfsadmin -safemode enter