Secondary vs Standby NameNode

This video will explain about secondary and standby name nodes.
What is Secondary NameNode
What is Standby Namenode

[@kartikmishra1053]

Thank-you for the video.
Can we deploy Primary and Secondary NN on a single host ( Machine)?

[@sushilmaurya4405]

If I'm create namenode ha then running fine but after some time one node down how to enable that Namenode in case you're not able up that node then what can do for. Please reply to