Fully allocated volumes

A fully allocated volume contains both virtual capacity and real capacity, which are set when you create the volume.

Fully allocated volumes are created with the same amount of real capacity and virtual 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. In a basic volume, the virtual capacity and real capacity are the same. Fully allocated volumes are automatically formatted through the quick initialization process after the volume is created. This process makes fully allocated volumes available for use immediately. The system formats any new fully allocated volume copy by default. Quick initialization requires a small amount of I/O to complete and limits the number of volumes that can be initialized at the same time. Some volume actions such as moving, expanding, shrinking, or adding a volume copy are disabled when the specified volume is initializing. Those actions are available after the initialization process completes. Image-mode, thin-provisioned, and compressed volumes do not require quick initialization.

The quick initialization process can be disabled in circumstances where it is not necessary. For example, if the volume is the target of a Copy Services function, the Copy Services operation formats the volume.

The quick initialization process can also be disabled for performance testing so that the measurements of the raw system capabilities can take place without waiting for the process to complete.