With vCenter Server 5.5 Update 3 and later, Microsoft Cluster Service (MSCS) is supported as an option for providing vCenter Server availability.
Multiple instances of vCenter Server are in a MSCS cluster, but only one instance is active at a time. Use this solution to perform maintenance, such as patching or upgrades, on one node in the cluster without taking down the vCenter Server database.
Another potential benefit of this approach is that MSCS uses a type of "shared-nothing" cluster architecture. The cluster does not involve concurrent disk accesses from multiple nodes. In other words, the cluster does not require a distributed lock manager. MSCS clusters typically include only two nodes and they use a shared SCSI connection between the nodes. Only one server needs the disks at any given time, so no concurrent data access occurs. This sharing minimizes the impact if a node fails.
Unlike the vSphere HA cluster option, the MSCS option works only for Windows virtual machines and does not support thevCenter Server Appliance.