Multi-tier Power-Saving Method in Cloud Storage Systems for Content Sharing Services

Abstract

Fast-growing cloud computing has a mass impact on power consumption in datacenters. In our previous study, we presented a power-saving method for cloud storage systems, where the stored data were periodically rearranged in a disk array in the order of access frequency. The disk containing unpopular files can often be switched to power-saving mode, enabling power conservation. However, if such unpopular files became popular at some point, the disk containing those files spin up that leads to increase power consumption. To remedy this drawback, in this paper, we present a multi-tier power-saving method for cloud storage systems. The idea behind our method is to divide the disk array into multiple tiers. The first tier containing popular files is always active for fast response, while lower tiers pack unpopular files for power conservation. To maintain such a hierarchical structure, files are periodically migrated to the neighboring tiers according to the access frequency. To evaluate the effectiveness of our proposed method, we measured the performance in simulations and a prototype implementation using real access traces of approximately 60,000 time-series images with a duration of 3,000 h. In the experiments, we observed that our method consumed approximately 22% less energy than the system without any file migration among disks. At the same time, our method maintained a preferred response time with an overall average of 86 ms based on our prototype implementation.