While in Santa Clara, I attended the "NameNode HA" presentation by Sanjay Radia, and was very much impressed by it. Back to Houston, I re-told what I heard at Houston Hadoop Meetup, and was at a loss to explain exactly what is new in the HortonWorks project. I asked Sanjay, who graciously provided the details. With a little editing, it goes as follows.
To answer your question, Mark, there were no previous offerings like that, and certainly not from Cloudera. Cloudera does not have such an offering, and that is why they are working with us.
The only solution currently in use is Avatar NN which is used at Facebook for doing manual faiover.
So, what it different? Firstly, we deal with all the corner cases for fencing. Secondly, our NN HA is hot, not cold or warm. And thirdly - the NN does not have the necessary states such as Active and Standby - you can try to fake the safe mode to do that.
Our doc on the jira gives the details.
Art: Raja Ravi Varma - A Student