Compatibility with the capacity saving function
The capacity saving function is not compatible with certain products and functions.
The following table specifies the compatibility restrictions for the capacity saving function.
| Program product/function | Restrictions when using the capacity saving function |
| Dynamic Provisioning | The V-VOL full allocation function cannot be used. To prevent writing failures caused by full pool capacity, you must consider monitoring the free space of a pool. |
| Dynamic Tiering | Dynamic Tiering cannot be used. You must separate Dynamic Tiering pools and pools for which capacity saving is enabled. |
| Universal Volume Manager | The data direct mapping attribute cannot be set to DP-VOLs for which capacity saving is enabled. You must separate pools for which data direct mapping is applied and pools for which capacity saving is enabled. |
| ShadowImage quick restore | The ShadowImage quick restore function cannot be used. Therefore, it takes time when you restore the backup data and then resume the application. |
| Volume Migration | The Volume Migration product cannot be used on DP-VOLs for which capacity saving is enabled. If you need to migrate capacity saving-enabled DP-VOLs, use a different method to migrate the DP-VOLs (for example, host-based migration). |
| Accelerated compression |
The capacity saving function can be used with accelerated compression, but accelerated compression is effective only for certain tasks. In this case, you must select the appropriate function depending on the task, as described in the following table. |
The following table describes the behavior when capacity saving and accelerated compression are used.
| Capacity saving | Accelerated compression | Behavior | |
| Compression | Deduplication and compression | ||
| Disabled | Disabled | Enabled | Only accelerated compression is performed. The storage controller does not perform the compression/deduplication processing, so I/O performance is not impacted. |
| Enabled | Disabled | Disabled |
The storage controller compresses data and stores the compressed data in the pool. Controller-based compression and accelerated compression can be used simultaneously, but it is not recommended because performance would be degraded compared to use of only accelerated compression. |
| Disabled | Enabled | Enabled |
When identical data is stored in a pool, the storage controller keeps only one of copy of the data (deduplication). For compression, the storage controller automatically determines that accelerated compression can be used and uses it. The pool must consist of only FMDs, and accelerated compression needs to be enabled in all parity groups in the pool. |
| Disabled | Enabled | Disabled | The storage controller performs the deduplication and compression processing. The storage controller has the largest overhead of the capacity saving processing. |