Model for planning the number of optical disks needed to create and maintain a long-term electronic archive

Development of an analytical model that allows to estimate the number of optical disks needed annually to create and maintain a complete electronic archive of long-term storage of information, as well as the time costs associated with these processes. An analytical model is developed for archives based on single disks (disks are not combined into RAID structures). The model uses the following parameters as input data: the estimated (design) capacity of the archive; the capacity of the optical disks used; estimates of the time to write, read and control the integrity of optical disks; the time allocated for technical work in the archive (the actual recording of new data, the control of previously recorded disks, the recovery of failed); the probability of failure of the optical disk during storage; the probability of failure of the disk during recording (marriage). Considered 4 options for the functioning of the archive depending on the bandwidth of the equipment and describes the stages of each option. For each option, analytical expressions are obtained that allow to estimate annually the required number of optical disks (which largely determines the annual material costs), as well as the time of changing stages. In addition, for some variants, expressions are obtained to evaluate the possibility of achieving the design capacity of the archive.