You will also need an external key management solution (read "expensive") to hold the unlocking keys for the disks, unless you are also able to run OnTap 9.0 which is just out now in Release Candidate stage. OnTap 9.0 includes the capability to manage disk unlocking keys onboard.
Hope this helps you.
Bob Greenwald
Lead Storage Engineer, Consilio LLC
NCIE SAN, Data Protection
Kudos and accepted solutions are always appreciated.