Minor Description
With the default logging level (INFO), it is very difficult to diagnose a large HBase cluster that is having problems assigning regions because the HBase master logs a DEBUG message when it instructs a region-server to assign a region.
You actually have to crawl EVERY HBase region-server log to find out which node received the request for a particular region. Further, lets say the HBase master sends the request and something goes wrong, we might not even get a message in the region-server log.