A stretched cluster is a deployment model in which two or more virtualization host servers are part of the same logical cluster but are located in separate geographical locations.
In a stretched cluster the servers act as a single system to provide high availability (HA) and load balancing despite not being located in the same facility. A stretched cluster offers the advantage of enabling easy migration of virtual machines from one geographic location to another while maintaining network connections with the other servers within the cluster. This scenario can be useful if, for example, a hurricane or other natural disaster were expected to hit one location. In this case, critical virtual machines could be migrated to servers within the stretched cluster that are physically located in a different facility.
VMware vSphere Metro Storage Cluster is an example of a configuration option that allows IT professionals the ability to create and manage stretched clusters.