Major Description
The data locality of regions often plays a large role in the efficiency of HBase. Compactions are also expensive to execute, especially on very large tables. The balancer can do a good job trying to maintain locality (when tuned properly), but it is not perfect.
This creates a less-than-desirable situation where it's a costly operation to take a cluster with spotty poor locality (e.g. a small percentage of regionservers with poor locality).
We already have this information available via the ClusterStatus proto. We can easily write a shell command that can present regions which are lacking a certain percentage of locality.