Hi,
I want to check the best practice for a vCenter Server HA deployment in a 2-datacenter environment.
Datacenter A - Active vCenter HA Node
Datacenter B - Passive vCenter HA Node
What is the difference when I place the Witness vCenter HA Node in DC-A or DC-B, and one of the 2 DCs would be go offline?
Best Regards,
Andre
I recently stood up a VCHA in a single data center so I haven't tried across 2 DC's. I assume you have a stretched Layer 2 network to place heartbeat traffic between the active/passive/witness nodes? I don't think you can route that traffic.
As long as the witness node is available (on the heartbeat network) to the site that fail over occurred to it should work. So would say placement of the witness node is the tricky part.
Ron
If you only have 2 sites and want to deploy the active and passive node at different sites, it doesn't matter where you place the witness.
As an example:
Active node at site A, passive node and witness at site B:
If site A fails, the passive node at site B takes over because it can still reach the witness.
If site B fails, both nodes fail because the active node no longer works if it cannot connect to the witness.
Active node and witness at site A, passive node at site B:
If site A fails, both nodes are down, because the passive node can't take over if it can't connect to the witness.
If site B fails, nothing happens, because the active node is still active and working (because it can reach the witness).
In both scenarios there is a case where both nodes can be down. On the other hand, if you place the active node and witness together, there is no failover scenario and you could promote the passive node manually if the site with the active node and witness fails.
In addition to sk84 answer, you can set anti-affinity rules for witness and active/passive node to put them on separate ESXi hosts and datastores. That will prevent vCenter failure scenario when one host/datastore fails, but will not prevent of vCenter unavailability when whole site with the wittiness node fails.
You can read about possible options here:
Highly available VCSA & PSC 6.5 for two sites - Cloud well served
