When a user requests a machine, it can be provisioned on any reservation of the appropriate type that has sufficient capacity for the machine. You can apply a reservation policy to a blueprint to restrict the machines provisioned from a that blueprint to a subset of available reservations.
Reservation policies provide an optional and helpful means of controlling how reservation requests are processed. A reservation policy is often used to collect resources into groups for different service levels, or to make a specific type of resource easily available for a particular purpose. The following scenarios provide a few examples of possible uses for reservation policies:
To ensure that machines provisioned from a virtual blueprint are placed on reservations with storage devices that support NetApp FlexClone
To restrict provisioning of cloud machines to a specific region containing a machine image that is required for a specific blueprint
To restrict provisioning of Cisco UCS physical machines to reservations on endpoints on which the selected service profile template and boot policy are available
As an additional means of using a Pay As You Go allocation model for vApps
You can add multiple reservations to a reservation policy, but a reservation can belong to only one policy. You can assign a single reservation policy to more than one blueprint. A blueprint can have only one reservation policy.
A reservation policy can include reservations of different types, but only reservations that match the blueprint type are considered when selecting a reservation for a particular request. For more information about how reservations are selected for provisioning a machine, see IaaS Configuration for Cloud Platforms, IaaS Configuration for Physical Machines, or IaaS Configuration for Virtual Platforms.
If you have SDRS enabled on your platform, you can allow SDRS to load balance storage for individual virtual machine disks, or all storage for the virtual machine. If you are working with SDRS datastore clusters, conflicts can occur when you use reservation policies and storage reservation policies. For example, if a standalone datastore or a datastore within an SDRS cluster is selected on one of the reservations in a policy or storage policy, your virtual machine storage might be frozen instead of driven by SDRS.