4.1.5 Thin Provisioning Child Pools and VVols A thin-provisioned volume presents a different capacity to mapped hosts than the capacity  that the volume consumes in the storage pool. The IBM FlashSystem 9100 system supports  thin-provisioned volumes in both standard pools and Data Reduction Pools.  In Standard Pools, thin-provisioned volumes are created as a specific volume type that is  based on capacity savings criteria. These properties are managed at the volume level. With  Data Reduction Pools, all the benefits of thin-provisioning are available to all the volumes that  are assigned to the pool. Only fully allocated volumes do not gain these benefits. For the  thin-provisioned volumes in data reduction pools, you can also configure compression and  data deduplication on these volumes, increasing the capacity savings for the entire pool.  Data Reduction Pools enhance capacity efficiency for thin-provisioned volumes by monitoring  the hosts use of capacity. When the host indicates that the capacity is no longer needed, the  space is released and can be reclaimed by the Data Reduction Pool to be redistributed  automatically (UNMAP). Standard pools do not have these functions. The virtual capacity of a thin-provisioned volume is typically significantly larger than its real  capacity. Each system uses the real capacity 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. The system identifies  read operations to unwritten parts of the virtual capacity and returns zeros to the server  without using any real capacity.  For more details about storage system, pool, and volume capacity metric, see Chapter 8,  “Monitoring” on page 267. Thin-provisioned volumes can also help simplify server administration. Instead of assigning a  volume with some capacity to an application and increasing that capacity as the needs of the  application 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. It is important to monitor physical capacity, if you want to provide more space to your hosts  the you have physically available in you IBM FlashSystem 9100 storage subsystem. Details  on monitoring physical capacity of your storage and an explanation of the difference between  Thin provisioning and over allocation can be found at fount at 8.4, “Creating Alerts for IBM  Spectrum Control and IBM Storage Insights” on page 302. At the time of writing, Data Reduction Pools are created as parent pools only, so no Child  Pools are available for Data Reduction Pools. If you have to plan for VMware VVols, then Standard/Traditional Pools is the only option. Note:  Child Pools are only available in conjunction with Standard Pools. Chapter 4. Storage Pools  69