@NLAMA If you shutdown the Active Namenode, the Standby NameNode needs to become the Active NameNode, before it can serve any of you requests (which is the failover mechanism). So, once the ZFKC detects that the Standby Namenode needs to become the Active Namenode, it informs the Standby Namenode to start the services related to Active mode, which include updating the fsimage, rolling over the edit logs etc. This operation might take some time. Hence, the delay you mentioned. Killing of StandBy Namenode does not affect the Active Namenode, hence you don't see any delay in performing the hdfs operations. Hope this explains. Let me know if you have more doubts. Thanks! ... View more