Bryce: I've done that 2 times. What I've done is:
1) change the path to the new path in the Cold Storage Schema of Enterprise PDM Administration
2) tell your users not to connect to the PDM and exit from Solidworks
3) stop Solidworks enterprise PDM archive and database services on the Windows Server
4) move with a tool like robocopy or commercial software like viceversa or freeware like syncback
5) start Solidworks enterprise PDM archive and database services on the Windows Server
6) delete old "cold storage"
I've done the copy process ou of working hours (my archive is of more than 300 GB), I have FC disks and it took about an hour to move that data to the new folder.