As per small discussion here: http://search-hadoop.com/m/DZcdNHsTOe2, here are some extra things we might want to expose:
1. Splits stats.
We have in JMX flush and compaction data (time spent and data amount). Should we add also stats for split procedures as they affect hbase behaviour too?
2. Flush/Compaction/Split rate.
For flush and compaction we expose only time spent and data amount stats, but we might also want to show smth like operations "rate" (number of actions).
Based on flush/compaction/split rate one can make judgements on whether some configuration is properly set (e.g. hbase.hregion.memstore.flush.size).
3. Events log.
Also I think would be very useful for ops to have ability to watch at events (like splits, flushes, compactions) on a web interface/in JMX, know when they appear, aka events' log. Thus one can go to to web page and see what can affect performance degradation for a particular period of time. Currently we have to (and do) go to log files for that kind of info.