With the reservation pool allocation model, all the resources you allocate are immediately committed to the organization VDC. Users in the organization can control the overcommitment by specifying reservation, limit, and priority settings for individual virtual machines.
Because only one resource pool and one subresource pool are available in this model, the placement engine does not reassign a virtual machine's resource pool when it is powered on. The virtual machine's rate and limit are not modified.
With the reservation pool model, sources are always available when needed. This model also offers fine control over the virtual machine rate, limit, and shares, which can lead to optimal use of the reserved resources if you plan carefully. For information about configuring virtual machine resource allocation settings in reservation pool VDCs, see the vCloud Air - Virtual Private Cloud OnDemand User's Guide.
In this model, reservation is always done at the primary cluster. If sufficient resources are not available to create an organization VDC on the primary cluster, the organization VDC creation fails.
Other limitations of this model are that it is not elastic and organization users might set nonoptimal shares, rates, and limits on virtual machines, leading to underuse of resources.