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

You can increase the capacity of a virtual disk using the free capacity on the disk group of the standard virtual disk or the snapshot repository virtual disk.

The Total Unconfigured Capacity node, shown in the Storage & Copy Services tab, is a contiguous region of unassigned capacity on a defined disk group. When increasing virtual disk capacity, some or all of the free capacity may be used to achieve the required final capacity. Data on the selected virtual disk remains accessible while the process for increasing virtual disk capacity is in progress.