When you create a volume, you can designate that it is thin-provisioned to save capacity for the volume. A thin-provisioned volume presents a different capacity to mapped hosts than the capacity that the volume consumes in the storage pool. The 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. Standard pools do not have these features.
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.
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.