Major Description
From the thread "introducing nodes w/ more storage" (http://search-hadoop.com/m/DHED4azyle2), we should have a look at what happens when nodes of varying data density are used in a single cluster. The user would expect that nodes be filled according to their capacity, meaning an "even distribution" looks like all nodes at the same pct use. This behavior is probably in the intersection of hbase balancer and hdfs balancer. Probably this is made more complex by recent HDFS features such as HDFS-5682.
After investigation, let's fix it up to work better (if it's broken), and document the behavior in our awesome book.