** for vSphere 5.0 check this update! **
Today I received a very valid question around a full cluster failure. What happens when all the hosts in a cluster go down and at some point return? Will the VMs be restarted and what do I need to have in place to ensure they will?
It seems to be an urban myth that you need to use “auto-start” for a full cluster failure. But as you might have noticed that won’t work when HA is enabled. So what will?
Is it really that simple? Yes it is! When a full cluster fails and nodes start powering up HA will restart the VMs. As you know HA (or to be precise the primary nodes) maintains the host states, which includes the status of all VMs on those hosts. When one of the primary nodes returns to duty it will trigger the restarts based on the last known state. Make sure you set the restart priority correct so that any VMs hosting “management apps” will be booted up first.
It can’t get any simpler than that can it!