12.1. Rebalancing HDFS
This topic describes how you can initiate an HDFS rebalance from Ambari. HDFS provides a “balancer” utility to help balance the blocks across DataNodes in the cluster.
In Ambari Web, browse to Services > HDFS > Summary.
Select Service Actions, then choose Rebalance HDFS.
Enter the Balance Threshold value as a percentage of disk capacity.
Click Start to begin the rebalance. You can check rebalance progress or cancel a rebalance in process by opening the Background Operations dialog in Ambari.