What are active and passive NameNodes in Hadoop

Question

I am bit confused about the above terms, can you please help me know these terms.

Answer 1

In HA (High Availability) architecture, we have two NameNodes – Active “NameNode” and Passive “NameNode”.

• Active “NameNode” is the “NameNode” which works and runs in the cluster.
• Passive “NameNode” is a standby “NameNode”, which has similar data as active “NameNode”.

When the active “NameNode” fails, the passive “NameNode” replaces the active “NameNode” in the cluster. Hence, the cluster is never without a “NameNode” and so it never fails.