Dell EMC PowerVault MD 34XX/38XX Series Storage Arrays Administrator's Guide

When you configure a thin virtual disk, you can specify the following types of capacity:

• physical (or preferred)
• virtual

Virtual capacity is capacity that is reported to the host, while physical capacity is the amount of actual physical disk space allocated for data write operations. Generally, physical capacity is much smaller than virtual capacity.

Thin provisioning allows virtual disks to be created with a large virtual capacity but a relatively small physical capacity. This is beneficial for storage utilization and efficiency because it allows you to increase capacity as application needs change, without disrupting data throughput. You can also set a utilization warning threshold that causes MD Storage Manager to generate an alert when a specified percentage of physical capacity is reached.