A cluster is a collection of ESXi hosts and associated virtual machines with shared resources and a shared management interface. Before you can obtain the benefits of cluster-level resource management you must create a cluster and enable DRS.

Depending on whether or not Enhanced vMotion Compatibility (EVC) is enabled, DRS behaves differently when you use vSphere Fault Tolerance (vSphere FT) virtual machines in your cluster.

Table 1. DRS Behavior with vSphere FT Virtual Machines and EVC
EVC DRS (Load Balancing) DRS (Initial Placement)
Enabled Enabled (Primary and Secondary VMs) Enabled (Primary and Secondary VMs)
Disabled Disabled (Primary and Secondary VMs)

Disabled (Primary VMs)

Fully Automated (Secondary VMs)