CPU and memory configurations for virtual machines are highly configurable in ESXi. This gives the flexibility to configure the following:

• Shares: These allow an administrator to set a relative priority to a virtual machine's access to CPU or memory. When there is contention on the system, higher-priority workloads have a higher chance of using the resource.
• Reservations: These allow an administrator to guarantee CPU or memory to a virtual machine. In this case, no other resource will be able to utilize the assigned resources.
• Limits: These allow an administrator to limit the amount of physical resources that a virtual machine can consume. This can be useful in simulating contention or in preventing a resource from fully consuming CPU or memory resources.

To simplify configuration and administration, avoid using these parameters unless you have a clear reason to make changes. For example, if there is a critical application that must continue to receive resources, even during periods of resource contention, a reservation allows the resources to be available, and shares can be used to set relative priorities.