Which VM/Host rule ensures domain controllers run on separate ESXi hosts?

The option that ensures domain controllers run on separate ESXi hosts is known as the "Separate Virtual Machine" rule. This rule is specifically designed to enhance the availability and resilience of critical virtual machines, such as domain controllers, by ensuring that they are not co-located on the same physical host. By utilizing this rule, an administrator can minimize the risk of a single point of failure, as placing domain controllers on different hosts ensures that if one host experiences a failure, the other hosts continue to support operational needs.

Employing this rule is particularly important in environments where domain controllers are vital for authentication and directory services. This separation aids in maintaining uptime and reliability of these essential services.

The other options do not specifically address the requirement of distributing domain controllers across hosts. For instance, the "Virtual Machines to Hosts" rule focuses on placing specific VMs on designated hosts but does not guarantee separation among domain controllers. Similarly, the "Virtual Machines to Virtual Machines" rule pertains to the relationships and interactions between VMs rather than their physical placement, and "Keep Virtual Machines Together" explicitly aims to maintain VMs on the same host, which is counterproductive in ensuring high availability for critical services like domain controllers.