5.5

Pay-As-You-Go Allocation Model
With the pay-as-you-go allocation model, resources are committed only when users create vApps in the
organization virtual datacenter. You can specify a percentage of resources to guarantee, which allows you to
overcommit resources. You can make a pay-as-you-go organization virtual datacenter elastic by adding
multiple resource pools to its provider virtual datacenter.
Resources committed to the organization are applied at the virtual machine level.
When a virtual machine is powered on, the placement engine checks the resource pool and assigns it to
another resource pool if the original resource pool cannot accommodate the virtual machine. If a sub-
resource pool is not available for the resource pool, vCloud Director creates one with an infinite limit and
zero rate. The virtual machine's rate is set to its limit times its committed resources and the virtual machine
is placed, and the virtual machine placement engine places the virtual machine on a provider virtual
datacenter resource pool.
The benefit of the pay-as-you-go model is that it can take advantage of new resources added to the provider
virtual datacenter.
In rare cases, a virtual machine is switched from the resource pool it was assigned at creation to a different
resource pool at power on because of a lack of resources on the original resource pool. This change might
involve a minor cost to move the virtual machine disk files to a new resource pool.
In the pay-as-you-go model, no resources are reserved ahead of time, so a virtual machine might fail to
power on if there aren't enough resources. Virtual machines operating under this model cannot take
advantage of the resources of idle virtual machines on the same subresource pool, because resources are set
at the virtual machine level.
Reservation Pool Allocation Model
All of the resources you allocate are immediately committed to the organization virtual datacenter. Users in
the organization can control 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 virtual machine rate, limit, and shares, which can lead to optimal use of the reserved resources
if you plan carefully.
In this model, reservation is always done at the primary cluster. If sufficient resources are not available to
create an organization virtual datacenter on the primary cluster, the organization virtual datacenter 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.
Create an Organization
Creating an organization involves specifying the organization settings and creating a user account for the
organization administrator.
Procedure
1 Open the New Organization Wizard on page 28
Open the New Organization wizard to start the process of creating an organization.
Chapter 3 Creating and Provisioning Organizations
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