High Availability is a combination of components and configurations that allow continuous operation of a computational environment on a daily basis. Basically, it means that even when unattended server hardware goes bad in a live environment, High Availability can manage the server on its own and keep a virtual environment running by automatically migrating virtual machines from one node to another. A properly set up HA requires very little actual user interaction during hardware failure. Without HA in place, a system administrator will have to monitor the environment for failures and manually move or migrate virtual machines to healthy nodes.

In a small environment this can be manageable, but in a large environment of hundreds of virtual machines and nodes, constant monitoring is just not realistic. Although there can be monitoring software in place to automatically alert administrators about any node failure, without HA the administrator will have to manually...