With VMware Distributed Virtual Switch or DVS, one of the new features in the upcomming VMware VI4, allows you to create Virtual Switchs at a cluster level and assign ESX Servers to them. Up to now, in VI3, virtual switches can only be created at a host level, and if in a DRS/HA Cluster, these virtual switches are normally configured the same across all hosts. With DVS, you only have to create a virtual switch once and assign it to all hosts. It also allows you to migrate virtual machines on existing virtual networks to a new network all with a few clicks!
VMware Fault Tolerance, a new feature of VMware Virtual Infrastructure 4, provides the highest level on High Availability to Virtual Machines in the Virtual Infrastructure. Fault tolerance, in basic terms, creates a clone of a running virtual machine using VMotion technology. This then replicates, in real time, changes made on the primary virtual machine to the secondary virtual machine. Both virtual machines have the same IP address and the same MAC address.