the DFS balancer is that last thing you want to run in your HBase
cluster.That will break all the data locallity for the compacted regions.
On compaction, a region write the files on the local server first, then the
2 other replicates are going on different datanodes. so on read, HBase can
garantee that data is read from local datanode dans not from another
datanode over the network.
Have you run the HBase balancer? How many regions do you have per region