Thin-provisioned FlashCopy When a new volume is created, you can designate it as a  thin-provisioned volume , and it has  a virtual capacity and a 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 copy from a storage pool. In a fully allocated  volume, the virtual capacity and real capacity are the same. However, in a thin-provisioned  volume, the virtual capacity can be much larger than the real capacity. The virtual capacity of a thin-provisioned volume is typically larger than its real capacity. On  IBM Spectrum Virtualize based systems, the real capacity is used to store data that is written  to the volume, and metadata that describes the thin-provisioned configuration of the volume.  As more information is written to the volume, more of the real capacity is used. Thin-provisioned volumes can also help to simplify server administration. Instead of assigning  a volume with some capacity to an application and increasing that capacity following the  needs of the application if those needs change, you can configure a volume with a large  virtual capacity for the application. You can then increase or shrink the real capacity as the  application needs change, without disrupting the application or server. When you configure a thin-provisioned volume, you can use the warning level attribute to  generate a warning event when the used real capacity exceeds a specified amount or  percentage of the total real capacity. For example, if you have a volume with 10 GB of total  capacity and you set the warning to 80 percent, an event is registered in the event log when  you use 80 percent of the total capacity. This technique is useful when you need to control  how much of the volume is used. If a thin-provisioned volume does not have enough real capacity for a write operation, the  volume is taken offline and an error is logged (error code 1865, event ID 060001). Access to  the thin-provisioned volume is restored by either increasing the real capacity of the volume or  increasing the size of the storage pool on which it is allocated. You can use thin volumes for cascaded FlashCopy and multiple target FlashCopy. It is also  possible to mix thin-provisioned with normal volumes. It can be used for incremental  FlashCopy too, but using thin-provisioned volumes for incremental FlashCopy only makes  sense if the source and target are thin-provisioned. Data Reduction Pools (DRP) is a no charge feature that offers significant benefits on  implementing data reduction techniques such as compression and data deduplication (see  Chapter 4, “Storage Pools” on page 55). When using thin provisioned volumes on DRP also  consider implementing compression as it provides benefits such as: Therefore, the recommendation is to always enable compression on DRP thin provisioned  volumes. GLYPH<SM590000> Reduced amount of I/O operation to the back-end as the amount of data to be actually  written to the back-end reduces with compressed data. This is particularly relevant with a  poorly performing back-end, but less of an issue with the high performing back-end on  IBM FS9100. GLYPH<SM590000> Better back-end capacity monitoring, as DRP pools with thin provisioned uncompressed  volumes doesn’t provide physic al allocation information. GLYPH<SM590000> Space efficiency as the compressed data provides more capacity savings. 150  IBM FlashSystem 9200 and 9100 Best Practices and Performance Guidelines