Dear Learner,

Hope you are doing well.

Setting up a secondarynamenode is a concept of hadoop 1.x which is used to take the backup of namenode data and in case namenode goes down then we have to manually set the secondarynamenode as a primary namenode.

Setting up a active and passive namenode is a concept of hadoop 2.x in which both the namenodes runs simultaneously and if active namenode goes down then automatically passive namenode comes into the picture without any manual afford.

Feel free to contact us in case you have any query.