With VMware ESXi hosts, multiple server workloads are consolidated to one virtual server, and in case of a breakdown or a server failure, it is important to keep the services running. VMware HA helps the administrator achieve a sense of availability concerning minimum downtime for the servers. HA does not provide 100 percent availability of VMs, but rather provides higher availability by rapidly recovering VMs from failed hosts. HA monitors all ESXi hosts in a cluster, and in case a failure is detected, it automatically restarts the VM on a different host. To ensure this functionality, shared storage is needed.

Once a particular ESXi host has crashed, HA restarts those virtual machines on the remaining ESXi hosts in the failover cluster. It can also monitor virtual machines that run in a virtualized environment for guest operating system failures, which means that if the guest operating system of a VM fails, HA can even restart that VM on another ESXi host...