P/PA-SPTF: Parallelism-aware request scheduling algorithms for MEMS-based storage devices

MEMS-based storage is foreseen as a promising storage media that provides high-bandwidth, low-power consumption, high-density, and low cost. Due to these versatile features, MEMS storage is anticipated to be used for a wide range of applications from storage for small handheld devices to high capacity mass storage servers. However, MEMS storage has vastly different physical characteristics compared to a traditional disk. First, MEMS storage has thousands of heads that can be activated simultaneously. Second, the media of MEMS storage is a square structure which is different from the platter structure of disks. This article presents a new request scheduling algorithm for MEMS storage called P-SPTF that makes use of the aforementioned characteristics. P-SPTF considers the parallelism of MEMS storage as well as the seek time of requests on the two dimensional square structure. We then present another algorithm called PA-SPTF that considers the aging factor so that starvation resistance is improved. Simulation studies show that PA-SPTF improves the performance of MEMS storage by up to 39.2% in terms of the average response time and 62.4% in terms of starvation resistance compared to the widely acknowledged SPTF algorithm. We also show that there exists a spectrum of scheduling algorithms that subsumes both the P-SPTF and PA-SPTF algorithms.