Another useful distinction when talking about long timeframes is the amount of ongoing attention needed to maintain the data. A true archival medium is one that

Another useful distinction when talking about long timeframes is the amount of ongoing attention needed to maintain the data. A true archival medium is one that, if stored in a reasonable environment, can be ignored and still be read at the end. By contrast many of the "obvious" ways of keeping data involve copying or regenerating it periodically as media degrade.