Fault Tolerance
vSphere Fault Tolerance can be used to ensure a higher level of availability than what is offered by vSphere HA for your virtual machines. It provides continuous availability by having identical virtual machines running on separate ESXi hosts in a cluster.
A protected virtual machine is known as the primary VM and a duplicate, the secondary VM, is created and runs on another ESXi host within the cluster. A Primary VM and Secondary VM cannot run on the same host. The execution of the Secondary VM is identical to the Primary VM and is capable of taking over at any point with no interruptions. The Primary and Secondary VMs monitor one another continuously to ensure that a Fault Tolerant state is maintained. If a failure occurs on the host running the Primary VM, then the Secondary VM will be activated immediately to replace the Primary VM. A new Secondary VM will be started and Fault Tolerance will be automatically reestablished.
Atomic file locking is used on shared storage...
