Известия высших учебных заведений. Поволжский регион:Технические науки (Oct 2023)
Some results of the integrity control of optical discs with recording based on the results of four years of storage in the archive
Abstract
Background. When designing electronic archives of long-term storage based on write once optical disks, it is necessary to take into account many parameters, the most significant among which are: the probability of losing at least part of the stored information and the number of disks purchased annually to replace those that failed during storage due to degradation. Mathematical models that allow calculating the values of these parameters are based on the knowledge of the probability of failure of one optical disk with a recording. However, in practice, the value of this parameter is usually not reliably known. The aim of the work is to obtain an estimate of the probability of failure of one optical disk with a recording based on a full-scale experiment on storing electronic information on BD-R optical disks for several years. Materials and methods. To obtain an estimate of the desired parameter in 2018, an experimental archive was laid on BD-R type disks. In the beginning of the experiment, the time of reading information from each disk was estimated. MD5 checksums were rolled up to control the integrity of the information. Assessment of the state of disks in the archive is performed annually by monitoring the integrity of recorded files by MD5 amounts and monitoring the state of disks by measuring the time of reading information. Standard interval estimation methods used in statistics are used to process the results. Results. It was found that the surface of some disks degrades during storage, which is expressed in a strong decrease in the speed of reading information, but the information itself is reproduced without loss. Such degradation can lead to disruption of planned deadlines for monitoring the integrity of information and destabilization of the entire archive. Therefore, such disks should be replaced with new ones along with disks on which information loss is detected. Conclusions. The results of the study show that it is necessary to use two probability values for models of long-term electronic archives: the probability of loss of information on the optical disk and the probability of degradation of the optical disk without loss of information. Estimates of the values of both parameters are obtained based on the results of a full-scale experiment.
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