DLP Exception for scanning Sys admins from doing backups only

I'm trying to see if there is a possible way to set up  a DLP rule that would not scan  information going to an external storage device for particular users. 

EG: lets say Joe wants to make a backup for Jessy.  If Joe  logs in in Jessys computer then anything he extracts into the external drive wont be scanned (aka not slow down read/write speeds) 

In other words that particular segment  of scanning not work for  Joe but still scann him for Email, printer, etc.

NOW 

I would preffer if this is when Joe is in anothers user machine.  

and if possible to match a particular device  (provided by us).