Snapshot size limit exceeded.

In disk group 3 (DG3) of PowerVault MD1220, volume VD33-XEN-DATA33 says the limit has been exceeded. I've moved the VMs from this volume to others in case I need to make any changes.  I don't know what to do. This snapshot configuration is old. Other disk groups do not take snapshots.

One question, if I have RAID 5 why do I need snapshots?