We gathered several file traces [24] on SunOS 4.0.3c. This version of SunOS offers a ``C2 secure computing facility'' that includes the ability to produce a system call audit trail. Using this feature, we gathered three traces of a volunteer user performing his normal work activity over a period of two weeks. The first trace contains 25,441 invocations of previously enumerated system calls captured over 72 hours. The second trace contains 23,858 invocations captured over 52 hours, while the numbers for the third trace are 85,962 and 86, respectively. During these hours activity varied widely and included compilations, document production, data analysis and display, large file searches, news reading, printing, and other operations.
Our simulated cache manager used an LRU replacement policy. It stepped through the traces, maintaining the cache in accordance with the user file accesses. Since our trace data lacks file sizes, we defined cache size by number of files. We varied the cache size and for each cache size, we compared the results of prefetching against those without prefetching.