3. Choosing a vCloud Consumption Model : 3.2 vCloud Director Allocation Models : 3.2.3 Reservation Pool
   
3.2.3 Reservation Pool
As with the Allocation Pool and Pay As You Go models, the Reservation Pool allocation model applies charges for the pre-allocation of resources to an organization virtual datacenter. The fundamental difference from the Allocation Pool model is that the vCloud provider cannot overcommit resources because all CPU and memory resources are 100% guaranteed. However, the vCloud provider can specify a maximum number of virtual machines. Only the vCloud provider can expand or contract resources. The Reservation Pool is unique in that it offers consumers full resource management controls in the form of shares, reservations, and limits. This is similar to vSphere Resource Management.
The Reservation Pool represents a good fit for steady state workloads that require guaranteed performance. To make best use of this model, you should know the customer’s application profile well enough to optimize resource provisioning.
vCloud providers typically charge a premium for this type of allocation model because they cannot overcommit resources.