A cluster of virtual machines across physical hosts (also known as a cluster across boxes) protects against software failures and hardware failures on the physical machine by placing the cluster nodes on separate ESXi hosts. This configuration requires shared storage on an Fibre Channel SAN for the quorum disk.

The following figure shows a cluster-across-boxes setup.

Two virtual machines on two different physical machines (ESXi hosts) 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 must be on a SAN.

Virtual Machines Clustered Across Hosts
Clustering virtual machines across hosts

This setup provides significant hardware cost savings.

You can expand the cluster-across-boxes model and place multiple virtual machines on multiple physical machines. For example, you can consolidate four clusters of two physical machines each to two physical machines with four virtual machines each.

The following figure shows how you can move four two-node clusters from eight physical machines to two.

Clustering Multiple Virtual Machines Across Hosts
Clustering multiple virtual machines across hosts