VMware vCloud Director enables customers to build secure private clouds to deliver infrastructure as a service. vCloud Director has 3 different allocation models which are used to allocate resources to a tenant in the private cloud. Allocation Models within vCD are used to determine how resources are allocated to the Organization vDC and more than likely how your customer will be charged for these resources. Currently vCD has three different types of allocation models:
- Allocation Pool – only a percentage of the resources you allocate are committed to the organization vDC. You can specify the percentage, which allows you to overcommit resources.
- Pay-As-You-Go – allocated resources are only committed when users create vApps in the organization vDC. You can specify the maximum amount of CPU and memory resources to commit to the organization vDC.
- Reservation Pool – all of the resources you allocate are committed to the organization vDC.
Each allocation model has its own characteristics. These characteristics can be placed in two categories:
- Virtual Machine Level
- Resource Pool Level
The distinction between each of the Allocation Models is how resources are allocated or to use vSphere terminology how resources are reserved or limited. In order to guarantee resources to a VM or to an entire pool vCD will set a reservation. To avoid extreme contention vCD will also cap your resources by setting a limit. These reservations and limits will be set on a VM or Resource Pool level depending on the chosen allocation model.
Duncan Epping posted an article detailing everything you ever wanted to know about vCD allocation models.