A Utility-based Approach to Cost-Aware Caching in Heterogeneous Storage Systems

Modern single and multi-processor computer systems incorporate, either directly or through a LAN, a number of storage devices with diverse performance characteristics. These storage devices have to deal with workloads with unpredictable burstiness. Storage aware caching scheme— that partitions the cache among the disks, and aims at balancing the work across the disks — is necessary in this environment. Moreover, maintaining proper size for these partitions is crucial. The existing storage aware caching schemes assume linear relationship between cache size and hit ratio. But, in practice a (disk) partition may accumulate cache blocks (thus, choke the remaining disks) without increasing the hit ratio significantly. This disk choking phenomenon may degenerate the performance of the disk system. In this paper, we address this issue of disk choking and present a repartitioning framework based on the notion of marginal gains. Experimental results shows the effectiveness of our approach. We show that our scheme outperforms the existing storage-aware caching schemes while supplied with a workload showing the non-linear relationship between cache size and hit ratio.