Disk-based Storage Total capacity

The Data Domain is not like a regular NAS or even a Windows share with Quotas involved. EACH volume reports to the query as having the full amount of disk space. Until you add space to the volume then you will notice the capacity goes down X2. If you were to create two shares on a Windows machine with 2TB and not add quotas (Thus a hard limit to the size of the volume) and handed it up to your server both share do indeed have the same amount of data available to them. The CIFS machine does not know if one or the other volume will fill up or not so it reports that the two volumes have 2 TB available to it. BE does not know how much disk the machine has. It just knows what the potential volume size is for the two volumes thus 4TB.

Where it problem is the Data Domain device is not building set volumes sizes but allowing all the room in the file system for the share.