MICRO: A Multilevel Caching-Based Reconstruction Optimization for Mobile Storage Systems

High performance, highly reliable, and energy-efficient storage systems are essential for mobile data-intensive applications such as remote surgery and mobile data center. Compared with conventional stationary storage systems, mobile disk-array-based storage systems are more prone to disk failures due to their severe application environments. Further, they have very limited power supply. Therefore, data reconstruction algorithms, which are executed in the presence of disk failure, for mobile storage systems must be performance-driven, reliability-aware, and energy-efficient. Unfortunately, existing reconstruction schemes cannot fulfill the three goals simultaneously because they largely overlooked the fact that mobile disks have much higher failure rates than stationary disks. Besides, they normally ignore energy-saving. In this paper we develop a novel reconstruction strategy, called multi-level caching-based reconstruction optimization (MICRO), which can be applied to RAID-structured mobile storage systems to noticeably shorten reconstruction times and user response times while saving energy. MICRO collaboratively utilizes storage cache and disk array controller cache to diminish the number of physical disk accesses caused by reconstruction. Experimental results demonstrate that compared with two representative algorithms DOR and PRO, MICRO reduces reconstruction times on average 20.22% and 9.34%, while saving energy no less than 30.4% and 13%, respectively.