What is active and passive NameNode in Hadoop?

[#1]

What is the need of passive NameNode in Hadoop?

[#2]

The passive NameNode can be used in high availability configurations, to prevent single point of failure: https://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.6.4/bk_hadoop-high-availability/content/ch_HA-N....

[#3]

Also check out info on the standby NameNode: https://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.6.4/bk_hdfs-administration/content/get_ready_to...

[#4 · Accepted solution]

There is no such thing as a "passive" NameNode. Are you asking about the HA or non-HA configuration?

1. In an HA configuration, there is
   1. Active NameNode that serves user requests.
   2. Standby NameNode that generates periodic checkpoints. It can also take over the role of the Active if the previously active NameNode dies or becomes unresponsive.
2. In a non-HA configuration
   1. Primary NameNode that serves user requests.
   2. Secondary NameNode that generates periodic checkpoints. A secondary NameNode can never become the primary.

The terminology is unfortunately confusing.