A virtual category type reservation provides access to the provisioning services of a virtual machine deployment for a particular vRealize Automation business group. Available virtual reservation types include vSphere, Hyper-V, KVM, SCVMM, and XenServer.
A reservation is a share of the memory, CPU, networking, and storage resources of one compute resource allocated to a particular vRealize Automation business group.
A business group can have multiple reservations on one endpoint or reservations on multiple endpoints.
To provision virtual machines, a business group must have at least one reservation on a virtual compute resource. Each reservation is for one business group only, but a business group can have multiple reservations on a single compute resource, or multiple reservations on compute resources of different types.
In addition to defining the share of fabric resources allocated to the business group, a reservation can define policies, priorities, and quotas that determine machine placement.
To provision successfully, the reservation must have sufficient available storage. The reservation's storage availability depends on:
How much storage is available on the datastore/cluster.
How much of that storage is reserved for that datastore/cluster.
How much of that storage is already allocated in vRealize Automation
For example, even if the vCenter Server has storage available for the datastore/cluster, if sufficient storage is not reserved in the reservation then provisioning fails with a "No reservation is available to allocate..." error. The allocated storage on a reservation depends on the number of VMs (regardless of their state) on that specific reservation. See the VMware Knowledge Base article Machine XXX: No reservation is available to allocate within the group XXX. Total XX GB of storage was requested (2151030) at http://kb.vmware.com/kb/2151030 for more information.