Adjust the default values to better support the current level of customer host and network configurations.
Increase the default for property dfs.datanode.balance.bandwidthPerSec from 1 to 10 MB. Apply to DN. 10 MB/s is about 10% of the GbE network.
Increase the default for property dfs.datanode.balance.max.concurrent.moves from 5 to 50. Apply to DN and Balancer. The default number of DN receiver threads is 4096. The default number of balancer mover threads is 1000.