vCenter 6.5 HA Architecture Overview

A vCenter HA cluster consists of three vCenter Server Appliance instances. The first instance, initially used as the Active node and is cloned twice to a Passive node and to a Witness node. Together, the three nodes provide an active-passive fail over solution.

Deploying each of the nodes on a different ESXi instance protects against hardware failure. Adding the three ESXi hosts to a DRS cluster can further protect your environment.When vCenter HA configuration is complete, only the Active node has an active management interface (public IP). The three nodes communicate over a private network called vCenter HA network that is set up as part of configuration. The Active node and the Passive node are continuously replicating data.


All three nodes are necessary for the functioning of this feature. Compare the node responsibilities.

Active Node:

Runs the active vCenter Server Appliance instance
Uses a public IP address for the management interface
Uses the vCenter HA network for replication of data to the Passive node.
Uses the vCenter HA network to communicate with the Witness node.

Passive Node:

Is initially a clone of the Active node.
Constantly receives updates from and synchronizes state with the Active node over the vCenter HA network.
Automatically takes over the role of the Active node if a failure occurs.

Witness Node:

Is a lightweight clone of the Active node.
basically works as a quorum to protect against a split-brain situations.


  • vCenter HA network latency between Active, Passive, and Witness nodes must be less than 10 ms.
  • The vCenter HA network must be on a different subnet than the management network.
  • vCenter Server 6.5 is required.

I hope this will help you to plan your next vSphere upgrade with vCenter High Availability.

Happy Diwali 🙂


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