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Determination of the Probability of Failure of a RAID-Type Optical Disks Array over Several Years of Storage

The problem of determining the probability of information loss on a RAID array of optical disks (the probability of loss of readability of a RAID array) during long-term storage in an electronic archive is considered. Knowledge of this value is necessary to determine a number of parameters (in particular, the number of spare copies of information) when designing electronic information archives built on modern hardware and software solutions such as robotic optical disk libraries, in which the physical unit of information storage is a cartridge (a block of several optical disks), on which a RAID array can be created. It is usually impossible to replace single disks in a cartridge. A model for calculating the probability of failure of an array of RAID optical disks over a long storage time is constructed. An example of calculating this probability for real source data is shown. Recommendations are given on the interpretation of the results obtained in relation to the design of future archives.