Configuring and managing datastores

Datastores represent storage locations for virtual machine files. The VM vCenter Datastores form shows the most recent datastore availability and capacity information for the datastores, and allows you to manage how storage space is handled when provisioning VMs.

Use the VM vCenter Datastores form to make the most efficient use of space, reducing the amount of wasted space.

How Datastore Space Is Allocated

By allocating reserved space when a VM is requested and accounting for recently provisioned space, the user can be assured that sufficient space will still be available for provisioning when the request is fulfilled. To accomplish this, space on the datastore is processed as follows:
  • When a VM is requested, the amount of reserved space is incremented to account for the requested disk size (template size plus additional disk size). If the reserve space request fails because of insufficient space after discovery, a task to fix the issue is created for the cloud operator. If the VM request is canceled, the reserved space is decremented to remove requested disk space.
  • For automated provisioning, the datastore with the least disk space, but sufficient for the VM request, is automatically selected.
  • When the VM is provisioned, the reserved space is decremented to remove provisioned disk size, and recently provisioned space is updated to provisioned disk size.
  • Whenever a datastore is rediscovered and updated accordingly, the amount of recently provisioned space is reset to 0. When a VM that was provisioned from a ServiceNow instance is terminated, the provisioned space is released and the free space is incremented. If the workflow is canceled before the VM is provisioned, the reserved space is updated to remove not provisioned disk size.
  • When a VM is modified, the requested amount of space is reserved, and the reserved space field is updated. When the Modify VM workflow finishes, the reserved space is updated to decrease the disk size added and the recently provisioned space is increased. When the VM is terminated (Terminate VM), the recently provisioned space in all affected datastores is released.

When a catalog task is created and a cloud operator chooses a datastore, only those datastores with the enough space to continue are shown in the choice list.