vCenter High Availability (vCenter HA) protects vCenter Server Appliance against host and hardware failures. The active-passive architecture of the solution can also help you reduce downtime significantly when you patch vCenter Server Appliance.
After some network configuration, you create a three-node cluster that contains Active, Passive, and Witness nodes. Different configuration paths are available. What you select depends on your existing configuration.
vCenter Architecture Overview
A vCenter HA cluster consists of three vCenter Server Appliance instances. The first instance, initially used as the Active node, is cloned twice to a Passive node and to a Witness node. Together, the three nodes provide an active-passive failover 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 is continuously replicating data to the Passive node.
vCenter Three-Node Cluster
The three-node cluster consists of an active, passive, and witness node. A private network is used for communication between the three nodes.
All three nodes are necessary for the functioning of this feature. Compare the node responsibilities.
vCenter HA Nodes
Node
Active
- 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
- 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
- Is a lightweight clone of the Active node
- Provides a quorum to protect against a split-brain situation
vCenter HA Deployment Options
You can set up your vCenter HA environment with an embedded Platform Services Controller or with an external Platform Services Controller. If you decide to use an external Platform Services Controller, you can place it behind a load balancer for protection in case of Platform Services Controller failure.
vCenter HA with an Embedded Platform Services Controller
When you use vCenter HA with an embedded Platform Services Controller, the environment setup is as follows.
vCenter HA with an Embedded Platform Services Controller
- The user provisions the vCenter Server Appliance with an embedded Platform Services Controller.
- Cloning of the vCenter Server Appliance to a Passive and a Witness node occurs.
- In a Basic configuration, the configuration creates and configures the clones.
- In an Advanced configuration, the user creates and configures the clones.
- As part of the clone process, Platform Services Controller and all its services are cloned as well.
- When configuration is complete, vCenter HA performs replication to ensure that the Passive node is synchronized with the Active node. The Active node to Passive node replication includes Platform Services Controller data.
- When configuration is complete, the vCenter Server Appliance is protected by vCenter HA. In case of failover, Platform Services Controller and all its services are available on the Passive node.
vCenter HA with an External Platform Services Controller
When you use vCenter HA with an external Platform Services Controller, you must set up an external load balancer to protect the Platform Services Controller. If one Platform Services Controller becomes unavailable, the load balancer directs the vCenter Server Appliance to a different Platform Services Controller.
vCenter HA with External Platform Services Controller
- The user sets up at least two external Platform Services Controller instances. These instances replicate vCenter Single Sign-On information and other Platform Services Controller information, for example, licensing.
- During provisioning of the vCenter Server Appliance, the user selects an external Platform Services Controller.
- The user sets up the vCenter Server Appliance to point to a load balancer that provides high availability for Platform Services Controller.
- The user or the Basic configuration clones the first vCenter Server Appliance to create the Passive node and Witness node.
- As part of the clone process, the information about the external Platform Services Controller and the load balancer is cloned as well.
- When configuration is complete, the vCenter Server Appliance is protected by vCenter HA.
- If the Platform Services Controller instance becomes unavailable, the load balancer redirects requests for authentication or other services to the second Platform Services Controller instance.
