As virtual environments grow, organizations can and will add multiple ESX/ESXi hosts to handle the workload of the ever-increasing, sometimes exponentially increasing, number of virtual machines. Some of the concerns with adding a number of stand-alone ESX/ESXi hosts, even those managed by vCenter Server, include the following issues:
What happens when a host fails?
How can I effectively balance the load across more than one ESX/ESXi host?
VMware vSphere 4 handles both of these issues by creating a cluster of ESX/ESXi hosts.
What is a cluster? A cluster is 2 to 32 ESX/ESXi hosts that work cooperatively to provide features such as VMware HA and VMware DRS. Clusters themselves are implicitly resource pools; however, ...