Does the IFS implemented in V7R1 have built in data de-duplication ...
If so, how can we activate it?
All compression algorithms use de-duplication in one form or another. To activate it under IBM i, search "disk compression" or similar in the Information Center. IIRC you IPL in manual mode and use DST menus to activate and deactivate compression at the ASP level, where some disks may be compressed, others not. Compression will add a little CPU overhead, but no changes to any IBM i interfaces or applications.