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

Similar to a disk group, you can create one or more virtual disks in a disk pool. However, the disk pool differs from a disk group in the way data is distributed across the physical disks comprising the pool. Dynamic Disk Pool (DDP) feature dynamically distributes data, spare capacity, and protects information across a pool of disk drives.

In a disk group, data is distributed across the physical disks based on RAID level. You can specify a RAID level when you create the disk group, then the data for each virtual disk is written sequentially across the set of physical disks comprising the disk group.