SoAP: A Strip-oriented Asynchronous Prefetching for Improving the Performance of Parallel Disk Systems

We propose a Strip-oriented Asynchronous Prefetching (SoAP) for the parallel disk systems. This technique splits a prefetching request into multiple independent prefetching sub-requests, each of which contains a full data strip to exploit the maximum physical sequentiality of involved disks. In addition, SoAP associates each prefetching sub-request with a relative large time window, allowing every disk in the parallel disk system to flexibly schedule its own prefetching sub-requests with less strict deadlines. To validate SoAP, we implemented a prototype of SoAP by modifying the Software RAID under Linux. Experimental results demonstrate that SoAP outperforms the Linux-like SEQP, STEP and ASP. Compared with SEQP, STEP and ASP, SoAP can speed up the average response time by up to 43.6\%, 32.8\% and 43\%, respectively, and improve system throughput by a factor of 2.6, 1.5 and 3.5, respectively. In a word, SoAP can significantly improve the response time and the throughput of the parallel disk systems simultaneously.