Leveraging Compressed Cache To Improve Disk Performance

The management of on-board disk cache plays an important role on disk performance, because it can bridge the gap between the high-speed I/O bus and slow magnetic media. The physical media of on-board disk cache is normally made of SRAM. However, it is very expensive and more capacity of cache chips brings much complexity to hardware design and thermal control. So, how to improve the utilization of the on-board disk cache is a key issue faced by manufactures, due to the performance and cost consideration.This paper proposes a new approach to alleviate this issue by compressing the on-board disk cache. The compressed cache provides more effective capacity to prefetch more sectors, which can improve the data transmission efficiency of disk storage system., and achieve the effect of performance optimization and energy consumption saving. Our researches and contributions are as follows:(1) This paper displays a new disk architecture to increase the effective capacity of disk on-board cache by adopting compressed data layer. To minimize the complexity and side effect of compression, we only compress the sectors fetched by read-ahead, and the used sectors and dirty sectors are kept as original format.(2) Hard disks are very sophisticated devices that have to be simulated with very accurate means. The scheme is implemented and integrated into DiskSim, and it models the behavior of hard disks exactly.Synthetic traces are employed to evaluate the proposed method. Experimental results demonstrate that the average response time can be reduced up to 25% with the improvement of the compression ratio, and the hit ratio gets up to 3x improvement. In addition, the performance of some services can be boosted up to 18% by testing real traces.