Major Description
From Adam w.r.t. HFile splitting:
There's actually a good number of messages of that type (HFile no longer fits inside a single region), unfortunately I didn't take a timestamp on just when I was running with the patched jars vs the regular ones, however from the logs I can say that this is occurring fairly regularly on this system. The cluster I tested this on is our backup cluster, the mapreduce jobs on our production cluster output HFiles which are copied to the backup and then loaded into HBase on both. Since the regions may be somewhat different on the backup cluster I would expect it to have to split somewhat regularly.
This JIRA complements HBASE-3721 by parallelizing HFile splitting which is done in the main thread.