Bit preservation: A solved problem

For years, discussions of digital preservation have routinely featuredcommentssuchas“bitpreservationisasolvedproblem; the real issues are...”. Indeed, current digital storage technologies are not just astoundingly cheap and capacious, theyareastonishinglyreliable. Unfortunately,theseattributes drive a kind of “Parkinson’s Law ” of storage, in which demands continually push beyond the capabilities of systems implementable atan affordableprice. Thispaper is infour parts: • Claims, reviewing a typical claim of storage system reliability, showing that it provides no useful information for bitpreservation purposes. • Theory, proposing “bit half-life ” as an initial measure of bit preservation performance, expressing bit preservation requirements in terms of it, and showing that the requirements being placed on bit preservation systems are so onerous that the experiments required to prove that a solutionexists arenot feasible. • Practice, reviewing recent research into how well actual storage systems preserve bits, showing that they fail to meet therequirements bymany orders ofmagnitude. • Policy, suggesting ways of dealing with this unfortunate situation