One key concern we had was whether the benefit from our predictive cache would quickly diminish as the size of our cache grew. In order to investigate this we simulated an LRU cache and our predictive cache for varying cache sizes up to 256 megabytes. Figures 5 shows how the cache hit ratios varied as we increased the cache size. From these graphs it is clear that tracking file system actions offers a performance gain that will not easily be overcome by increasing the size of an LRU cache. For example, on average it would require a 90 megabyte LRU cache to match the performance of a 4 megabyte predictive cache.
5 : Cache hit ratio versus cache size for both predictive cache and LRU (cache sizes 1--128 megabytes).