Preservation environments manage digital records for time periods that are much longer than that of a single vendor product. A primary requirement is the preservation of the authenticity and integrity of the digital records while simultaneously minimizing the cost of long-term storage, as the data is migrated onto successive generations of technology. The emergence of low-cost storage hardware has made it possible to implement innovative software systems that minimize risk of data loss and preserve authenticity and integrity. This paper describes software mechanisms in use in current persistent archives and presents an example based upon the NARA research prototype persistent archive.