Where backup data is meant to be used as a recovery resource in case of data loss, another possible use of low-cost mass storage media is archiving. The current trend of producing data in an electronic form, rather than on paper, calls for a need to have a valid archiving solution. Documents like contracts, payroll records, employee records, etc. will need to be stored in a permanent way, without losing the advantages of the electronic form they exist in.
A typical difference between backup data and archived data is their lifetime and dynamism. While backup data changes very fast and becomes obsolete in a short term period, archived data typically is static and stays current for a long time (up to several years, depending on legal standards). As a result, backup products should be able to differentiate between these two types of data, since storage policies will differ.
Besides a difference in handling this data, the storage device and media will have specific needs. Since data will be kept for a long time, media lifetime must be very high, which means you might need tape devices that are backward compatible.
Physical storage is as important. It should be an environmentally controlled, secured area.
Finally, availability of this data should be very high. That is why some sources suggest keeping a second backup server, entirely identical to the production system, on standby in a remote location, together with an extra copy of the media.