Consider using the Space Savings Estimation Tool (SSET). Access to SSET can
be provided via a NetApp account representative or via a NetApp partner.
SSET is a utility that runs on a client, and will provide an estimate for
NetApp deduplication savings within +-5% for the data. The data itself does
not need to be stored on a NetApp system for SSET to be used. There is a
README file bundled with the utility that contains details.