E-HASH: An Energy-Efficient Hybrid Storage System Composed of One SSD and Multiple HDDs

Abstract

In this paper, we describe a novel architecture for Energy-efficient Hybrid storAge system composed of a flash memory-based solid state disk (SSD) and multiple hard disk drives (HDD) called E-HASH. We arrange SSD and HDDs in a horizontal style. The SSD stores the most frequently read data and the HDDs store a log of update distance between currently accessed I/O blocks and their corresponding original blocks and handle all the writes. In consideration of disk energy saving, the distance and original data will be merged periodically. Consequently, the underutilized HDD can gain more chance to switch to low power state even spin down. E-HASH makes use of the fast read performance of SSD and the considerably high sequential write speed of mechanical HDDs to maximize system performance. The lifespan of SSD is prolonged due to avoidance of online writes. Our trace-driven simulation combined with a popular storage simulator has been implemented to evaluate E-HASH performance. Compared with most of existing SSD/HDD hybrid architectures, our experimental results show that E-HASH reduces average I/O response time by 72% to RAID and 53% to existing SSD/HDD storage hierarchies. The energy consumption is reduced by 61% and 45.2%, respectively.