Data block prefetching and caching in a hierarchical storage model

Storage subsystems have become one of the most important components in computer systems nowadays and have been expanded to include all three levels of memory hierarchy, namely the cache, the secondary and the tertiary storage. This paper presents a study of data block prefetching and caching over the two upper storage levels in a hierarchical storage model, by proposing techniques for data amortization from tertiary to secondary and from secondary to cache levels. Each level reserves a speci®c area for data prefetching and an evolutionary algorithm is proposed for identifying the data blocks to be prefetched in each of the two upper storage levels. An analytic model is proposed such that the cache, the secondary and the tertiary storage are appropriately parameterized in order to analyse the expected performance improvement due to prefetching. The data object prefetching approach is experimented under certain workload of requests referring to all storage levels and has shown signi®cant performance improvement with respect to request service times, as well as cache and secondary storage hit ratios. Ó 2000 Elsevier Science Inc. All rights reserved.