Determination of the required number of optical disks organized into hybrid structures for the purpose of development and maintenance of long-term electronic archives

Hybrid structures of optical disks are a method of archival storage of information with increased reliability, similar to RAID arrays of disks. Unlike classic RAID arrays in hybrid structures, one of the copies of information is stored on single disks that provides quick and easy access to information using just one standard drive. During long-term storage, optical disks with recording can degrade. Knowing the number of optical disks that will need to be purchased yearly to create an archive and then to maintain its integrity is necessary for planning the life cycle of the archive and the costs of its maintenance at the design stage. The paper presents analytical models that allow one to determine the required number of optical disks yearly for four possible options (strategies) for filling the archive as well as time points that characterize the process of filling the archive and to assess the principal achievability of the planned archive capacity. An example of a real calculation is given.