It is recommended that you run the HDFS balancer periodically. Why? (Choose 3)

A.
To improve data locality for MapReduce tasks.

B.
To ensure that there is capacity in HDTS for additional data.

C.
To help HDFS deliver consistent performance under heavy loads.

D.
To ensure that all blocks in the cluster are 128MB in size.

E.
To ensure that there is consistent disk utilization across the DataNodes.

Explanation:
http://hadoop.apache.org/docs/hdfs/r0.21.0/api/org/apache/hadoop/hdfs/server/balancer/Balancer.
html