We reached a significant milestone in HDFS: the Namenode HA branch was merged into the trunk. With this merge, HDFS trunk now supports HOT failover.
Significant enhancements were completed to make HOT Failover work:
We have extensively tested HOT manual failover in our labs over the last few months. The HDFS team is now working on completing automatic failover. Please see HDFS-1623 for more details.