High availability is the ability to restart virtual machines on other physical nodes in the event of a hardware failure or scheduled scenarios, which will be described in a moment. The configuration of high availability is accessible only for virtual machines that are allowed to perform automatic migration. It is recommended to configure high availability for virtual machines running mission-critical tasks. High availability ensures that the virtual machine will be restarted in the following scenarios:
When the virtualization host becomes nonoperational as a consequence of a hardware failure
When the virtualization host goes into maintenance mode for scheduled downtime
When the communication between the host and external storage or between hosts is lost
When the virtual machine is no longer available due to a failure of the virtual guest operating system.
With a highly available VM, service downtime is reduced to a minimum since the virtual machine will restart automatically...