DataDomain Deduplication Question

We are quickly running out of space on our DDs and would like to figure out how the Dedupe works to see what we can do.

For our back up, we are currently backing up to DD using NetBackup Backup Policy per Folders in File Server. We have found that the users are now duplicating files across folders and we would like to find out if this is increasing the rate of our data growth.

So our question is will this duplication of files across folders be deduplicated within DataDomain?

Our thought is if the Backup Policies have its own Deduplication metadata, there will only be deduplication within a given folder (backup policy) and not across folders (across policies). But if the array holds single deduplication metadata, the files will be deduplicated no matter what folder/backup policy it resides in).

Please let us know how this all works