What happens as a result of the failure?

Thanks. Please view this ref: http://www.vmware.com/pdf/vsphere4/r40/vsp_40_availability.pdf

“Failure Detection and Host Network Isolation

Agents communicate with each other and monitor the liveness of the hosts in the cluster. This is done through the exchange of heartbeats, by default, every second. If a 15-second period elapses without the receipt of heartbeats from a host, and the host cannot be pinged, it is declared as failed. In the event of a host failure, the virtual machines running on that host are failed over, that is, restarted on the alternate hosts with the most available unreserved capacity (CPU and memory.)

NOTE : In the event of a host failure, VMware HA does not fail over any virtual machines to a host that is in maintenance mode, because such a host is not considered when VMware HA computes the current failover level. When a host exits maintenance mode, the VMware HA service is reenabled on that host, so it becomes available for failover again.

Host network isolation occurs when a host is still running, but it can no longer communicate with other hosts in the cluster. With default settings, if a host stops receiving heartbeats from all other hosts in the cluster for more than 12 seconds, it attempts to ping its isolation addresses. If this also fails, the host declares itself as isolated from the network.

When the isolated host’s network connection is not restored for 15 seconds or longer, the other hosts in the cluster treat it as failed and attempt to fail over its virtual machines. However, when an isolated host retains access to the shared storage it also retains the disk lock on virtual machine files. To avoid potential data corruption, VMFS disk locking prevents simultaneous write operations to the virtual machine disk files and attempts to fail over the isolated host’s virtual machines fail. By default, the isolated host shuts down its virtual machines, but you can change the host isolation response to Leave powered on or Power off. See “Virtual Machine Options,” on page 23.

NOTE If you ensure that your network infrastructure is sufficiently redundant and that at least one network path is available at all times, host network isolation should be a rare occurrence. ”