anchor.diff:  [[upgrade2.2]]
   === Upgrade from 2.0 or 2.1 to 2.2+
   
  -HBase 2.2+ uses a new Procedure form assiging/unassigning/moving Regions. It does not process HBase 2.1 and 2.0's Unassign/Assign Procedure types. Upgrade requires that we first drain the Master Procedure Store of old style Procedures before starting the new 2.2 Master. So you need to make sure that before you kill the old version (2.0 or 2.1) Master, there is no region in transition. And once the new version (2.2+) Master is up, you can rolling upgrade RegionServers one by one.
  +HBase 2.2+ uses a new Procedure form assigning/unassigning/moving Regions. It does not process HBase 2.1 and 2.0's Unassign/Assign Procedure types. Upgrade requires that we first drain the Master Procedure Store of old style Procedures before starting the new 2.2 Master. So you need to make sure that before you kill the old version (2.0 or 2.1) Master, there is no region in transition. And once the new version (2.2+) Master is up, you can rolling upgrade RegionServers one by one.
   
   And there is a more safer way if you are running 2.1.1+ or 2.0.3+ cluster. It need four steps to upgrade Master.
   
  
positive.code: [[upgrade2.0.logging]]
  .Changed logging
  HBase-2.0.0 now uses link:https://www.slf4j.org/[slf4j] as its logging frontend.
  Prevously, we used link:http://logging.apache.org/log4j/1.2/[log4j (1.2)].
  For most the transition should be seamless; slf4j does a good job interpreting
  _log4j.properties_ logging configuration files such that you should not notice
  any difference in your log system emissions.
  
negative.code: [[upgrade2.0]]
  === Upgrading from 1.x to 2.x
  
  In this section we will first call out significant changes compared to the prior stable HBase release and then go over the upgrade process. Be sure to read the former with care so you avoid surprises.
  
  ==== Changes of Note!
  
  