Description: The steady increase in the power and complexity of modern computer systems has encouraged the implementation of automatic file migration systems which move files dynamically between mass storage devices and disk in response to user reference patterns. Using information describing thirteen months of text editor data set file references, (analyzed in detail in the first part of this paper), they develop and evaluation algorithms for the selection of files to be moved from disk to mass storage. They find that algorithms based on both the file size and the time since the file was last used work well. The best realizable algorithms tested condition on the empirical distribution of the times between file references. Acceptable results are also obtained by selecting for replacement that file whose size times time to last reference is maximal. Comparisons are made with a number of standard algorithms developed for paging, such as Working Set. Sufficient information (parameter values, fitted equations) is provided that our algorithms may be easily implemented on other systems.
Date: October 1, 1978
Creator: Jay Smith, Alan
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