VMware High Availability (VMware HA) monitors your virtual infrastructure for ESX Server host failures and restarts virtual machines that are interrupted by those failures on alternate hosts. Starting with ESX Server 3.5, VMware HA can also detect and handle the failures of individual virtual machines and respond appropriately based on your specifications. With this additional functionality, called Virtual Machine Failure Monitoring, VMware HA deals with both host operating system and guest operating system failures.