Fully allocated volumes

A fully allocated volume is created when the real capacity of the volume equals the virtual capacity and real capacity.

A volume's capacity can be considered in terms of its virtual capacity and its real capacity. Virtual capacity is the volume storage capacity that is available to a host. Real capacity is the storage capacity that is allocated to a volume from a pool. Fully allocated volumes are created with the real capacity equal to the virtual capacity.

By default, fully allocate volumes are automatically formatted by a background process after the volume is created. During this process, some system resources are used to make the volume available for immediate use and ensures the volume is clear of any prior data. The time taken to format is governed by the size of the volume and the mirror synchronization rate of the volume. Increasing the synchronization rate reduces the time taken to format the volume by using additional system resources. The progress and estimated completion time of each volume format process is reported by the system.

Because the formatting process uses some system resources, there is a limit on the number of volumes that can be initialized at the same time. Also, some volume actions such as moving, expanding or shrinking the volume, or adding a volume copy are disabled until formatting is complete.

If it is not necessary for a fully allocated volume to be cleared of data when it is created, the formatting process can be skipped. Skipping formatting can also be useful if the volume will be the target of a Copy Services function because the Copy Services operation formats the volume.