A cluster of MSCS virtual machines on a single host (also known as a cluster in a box) consists of clustered virtual machines on the same ESXi host. The virtual machines are connected to the same storage, either local or remote. This configuration protects against failures at the operating system and application level, but it does not protect against hardware failures.
Windows Server 2008 R2 and above releases support up to five nodes (virtual machines). Windows Server 2003 SP2 systems support two nodes.
The following figure shows a cluster in a box setup.
Two virtual machines on the same physical machine (ESXi host) run clustering software.
The virtual machines share a private network connection for the private heartbeat and a public network connection.
Each virtual machine is connected to shared storage, which can be local or on a SAN.