Which setting on a virtual machine ensures it always gets the appropriate resources during host overload?

The setting that guarantees a virtual machine always receives the necessary resources, particularly during host overload scenarios, is CPU and Memory Reservations. Reservations allocate a specific amount of CPU and memory resources to a virtual machine, ensuring that these resources are always available to it, regardless of the overall demand on the host system.

When reservations are set, the hypervisor prioritizes the designated amounts for the virtual machine, protecting it from resource contention with other virtual machines, especially in environments where resource allocation is dynamically managed. This is crucial in maintaining performance and availability for critical applications running on that virtual machine.

While adjusting CPU and memory shares to high can improve resource allocation during contention, it does not guarantee availability. Likewise, High Availability Admission Control helps ensure that VMs will restart in the event of a host failure but does not pertain to resource allocation during normal operation. The High Performance Power Policy is focused on maximizing resource performance but does not influence allocation under overload conditions. Thus, CPU and Memory Reservations are the most effective mechanism to secure essential resources for a virtual machine in such situations.