OPTIMAL BACKUP STRATEGY FOR MAKING FILES BY COMPUTER

抄録

When we make document files by a computer or a wordprocessor, we sometimes meet with the accident that all the files having been stored in the floppy disk are lost and cannot be reconstructed. In order to avoid this kind of accident, we sometimes make a backup copy of the floppy disk which is useful when the original floppy disk is broken. We make a stochastic model which is useful to make a decision about whether or not to make a backup disk when there are k files in the floppy disk whose backup copy does not exist, we should make remaining n new files, and the probability that the accident occurs is p. The problem is formulated by dynamic programming and several properties of the optimal strategy are obtained. The case that the true value of p is unknown is also discussed and several properties have been obtained.