There is disclosed a computer system operable to process a plurality of logical storage unit manifests the manifests comprising respective pluralities of chunk identifiers identifying data chunks in a deduplicated data chunk store The computer system can determine at least one preferred manifest or preferred combination of manifests according to levels of duplication of the chunk identifiers within respective said manifests, and/or within respective combinations of said manifests. The computer system can provide preferred seed data corresponding to data chunks identified by the at least one preferred manifest or preferred combination of manifests. A method and computer readable medium are also disclosed. At least some embodiments facilitate timely and convenient transfer and storage of relevant data chunks to a receiving deduplicated data chunk store of a data storage system.