What happens during a failure?
When a host running the Primary virtual machine fails, a transparent failover occurs to the corresponding Secondary virtual machine. During this failover, there is no data loss or noticeable service interruption. In addition, VMware HA automatically restores redundancy by restarting a new Secondary virtual machine on another host. Similarly, if the host running the Secondary virtual machine fails, VMware HA starts a new Secondary virtual machine on a different host. In either case there is no noticeable outage.