Volumes can be configured to be thin-provisioned. A thin-provisioned volume behaves the
same as a fully provisioned volume regarding application reads and writes. However, when a
thin-provisioned volume is created, it is possible to specify two capacities: the real physical
capacity that is allocated to the volume from the storage pool, and its virtual capacity that is
available to the host.
The real capacity determines the quantity of extents that are initially allocated to the volume.
The virtual capacity is the capacity of the volume that is reported to all other components (for
example, FlashCopy and cache) and to the host servers