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

Repositories are system-created virtual disks used to hold write data for a snapshots, snapshot groups and consistency groups. During creation of either group or write-enabled snapshot virtual disk, an associated repository is automatically created. By default, one individual repository virtual disk is created for each group or snapshot. You can create the overall repository automatically using the default settings, or you can manually create the repository by defining specific capacity settings.

A snapshot virtual disk allows the host access to a copy of the data contained in a snapshot image. A snapshot image is not directly read or write accessible to the host and is used only to save data captured from the base virtual disk.