Balance data in a federation

Depending on your requirements, you can use the HDFS Balancer to balance data either at the level of the DataNodes or the block pools in a cluster with federated NameNodes.

Balancer balances only data across the cluster and not the namespace.

Run the Balancer using the hadoop-daemon.sh start command.

hadoop-daemon.sh start balancer [-policy <policy>]

Specify either of the following values for policy:

datanode: The default policy that balances data at the level of the DataNode.
blockpool: Balances data at the level of the block pool.