# Capacity efficiency metrics

HPE SSMC reports several metrics that indicate the capacity efficiency of HPE 3PAR storage systems.

**Compaction ratios**

The compaction ratio for a virtual volume is the ratio of the virtual size compared to the physical space used for the virtual volume. For example, if a 10 GiB thinly provisioned base virtual volume uses 2.5 GiB of physical space, the compaction ratio is 4:1.

Compaction ratios are calculated as follows:

**Thinly provisioned base virtual volume**. The compaction ratio is the virtual size, divided by the physical space used for the volume.**Thinly deduplicated base virtual volume**. The compaction ratio is the virtual size, divided by the sum of the physical space used for the volume and the associated physical space in the Dedup Store.**Thinly provisioned virtual volume family**. The compaction ratio is the sum of the virtual sizes for the base volume and its snapshots, divided by the sum of the physical space used for the base volume and its snapshots.**Thinly deduplicated virtual volume family**. The compaction ratio is the sum of the virtual sizes for the base volume and its snapshots, divided by the sum of the physical space used for the base volume and its snapshots and associated physical space in the Dedup Store.**Fully provisioned virtual volume**. The compaction ratio is the sum of the virtual sizes of all base volumes and snapshots in the group, divided by the sum of the physical space used for the base volumes, snapshots, and Dedup Store.**Common provisioning group**. The compaction ratio is the sum of the virtual sizes of all base volumes and snapshots in the group, divided by the sum of the physical space used for the base volumes, snapshots, and Dedup Store.

**Deduplication ratios**

The deduplication ratio for a virtual volume is the ratio of the physical space that would have been used without deduplication, compared to the physical space used for the virtual volume. Deduplication ratios do not include savings from inline zero-block detection.

Deduplication ratios are calculated as follows:

**Thinly deduplicated base virtual volume**. The deduplication ratio is the size of the data written to the virtual volume, divided by the sum of the physical space used for the virtual volume and associated physical space in the Dedup Store.**Thinly deduplicated virtual volume family**. The deduplication ratio is the size of the data written to the base virtual volume and its snapshots, divided by the sum of the physical space used for the base virtual volume and its snapshots and associated physical space in the Dedup Store.**Common provisioning group**. The deduplication ratio is the size of the data written to all thinly deduplicated base virtual volumes and snapshots in the group, divided by the sum of the physical space used for thinly deduplicated virtual volumes in the group and associated physical space in the Dedup Store. The deduplication ratio for a common provisioning group can be higher than the deduplication ratio for individual virtual volumes in the group. This happens when Dedup Store pages are shared by multiple virtual volumes.

**Overprovisioning ratios**

Overprovisioning is when a storage system indicates to hosts that the amount of usable capacity is greater than the amount of system-usable storage space. In HPE SSMC, overprovisioning ratios are reported for common provisioning groups, with the ratios roughly being the difference between the virtual size of the volumes and the available physical space, divided by the physical space available for the volumes. For example, if the virtual size of the volumes in a common provisioning group is 400 GiB but only 320 GiB of physical capacity is available to the system, the overprovisioning ratio is 0.25:1 (25%).

For information on using CLI commands to display overprovisioning information, see the HPE 3PAR Command Line Interface Administrator Guide.