Figure 1-14 Example of a HyperSwap Volume 1.7.2 Thin provisioning Volumes can be configured to be  thin-provisioned  or  fully allocated . A thin-provisioned  volume behaves as though it were a fully allocated volume in terms of read/write I/O.  However, when a volume is created, the user specifies two capacities: the real capacity of the  volume and its virtual capacity. The  real capacity  determines the quantity of MDisk extents that are allocated for the volume.  The  virtual capacity  is the capacity of the volume that is reported to IBM Storwize V5000  Gen2 and to the host servers. The real capacity is used to store the user data and the metadata for the thin-provisioned  volume. The real capacity can be specified as an absolute value or a percentage of the virtual  capacity. The Thin Provisioning feature can be used on its own to create over-allocated volumes, or it  can be used with FlashCopy. Thin-provisioned volumes also can be used with the mirrored  volume feature.  30  Implementing the IBM Storwize V5000 Gen2 with IBM Spectrum Virtualize V8.2.1