The high availability of virtual server infrastructure.
The term high availability is mainly used for servers connected in the cluster, which is a grouping of multiple servers (nodes) to ensure high availability of services operated within the above mentioned cluster.
When server virtualization is a topic of high availability and clustering is very important. Since the loss due to hardware error increases the number of virtual servers on that physical host not operate. For this reason it is an integral part of the cluster virtual server infrastructure. Most important is to determine which service will be provided in the high availability.
For some Failover Clusters, the virtual machine service. It is therefore necessary to determine whether to provide high availability virtual machine, or just in the virtual server service included.
Each of these cases requires the creation and configuration of the cluster at a different level and has its pros and cons. However, always need at least two physical host hypervisor role installed.