Data de-duplication (“de-dupe”) allows IT organizations to replace aging tape systems with disk-based backup solutions and minimize the storage allocated to backup and data protection. The effectiveness of de-dupe technology is dependent on the data being protected. Data streams with little data repetitiveness provide disappointing results when processed through a block-level de-dupe engine. To avoid this problem, Assisted Mainframe De-Dupe (AMDD) technology can insure that filesystem block-level de-dupe products efficiently de-dupe tape backup streams received from IBM™ and/or compatible mainframes. By pre-processing backup tape volumes before sending the data to storage, AMDD insures that large amounts of unchanged data lines up on de-dupe block boundaries each time the data is sent to the de-dupe process engine. By providing “well-behaved” data to the de-dupe process, AMDD can improve the effectiveness of de-dupe processing and substantially reduce the storage used to backup critical mainframe DASD resources.