vCenter HA question and number of hosts

[jedijeff]

Hi. We are currently running vCenter in HA mode in a 4-node cluster (not VSAN). We are thinking of removing a node for something else, so the cluster will have 3-nodes. I know vCenter in HA mode creates anti-affinity rules for the active, peer and witness. So my concern is with only 3-nodes now, if we lost an ESXi host and the cluster is now 2-nodes will whatever appliance was on that host be started on 1 of the 2 hosts due to anti-affinity rules? Thanks,,,

[MikeStoica]

Did you create any anti-afinity rules? There is no witness in HA cluster. Three hosts are recommended.

[sk84]

There is always a failover if the active vCenter node fails. Previously, you had a 1:4 risk that the host with the active component fails. If you take a host out of the cluster, the chance increases to 1:3. That's all.

If a host fails on which only the passive component or the witness component resides, nothing happens. In the VCHA setup, 2 components must always communicate with eachother for the VCHA cluster to work. So either active and passive appliance, or active and witness appliance or passive and witness appliance (where there would be a failover in this case).

So my concern is with only 3-nodes now, if we lost an ESXi host and the cluster is now 2-nodes will whatever appliance was on that host be started on 1 of the 2 hosts due to anti-affinity rules?

See: vSphere HA and DRS Affinity Rules