Region-based Flash Caching with Joint Latency and Lifetime Optimization in Hybrid SMR Storage Systems

The frequent Read-Modify-Write operations (RMWs) in Shingled Magnetic Recording (SMR) disks severely degrade the random write performance of the system. Although the adoption of persistent cache (PC) and built-in NAND flash cache alleviates some of the RMWs, when the cache is full, the triggered write-back operations still prolong I/O response time and the erasure of NAND flash also sacrifices its lifetime. In this paper, we propose a Region-based Co-optimized strategy named Multi-Regional Collaborative Management (MCM) to optimize the average response time by separately managing sequential/random and hot/cold data and extend the NAND flash lifetime by a region-aware wear-leveling strategy. The experimental results show that our MCM reduces 71% of the average response time and 96% of RMWs on average compared with the Skylight (baseline). For the comparison with the state-of-art flash-based cache (FC) approach, we can still save the average response time and flash erase operations by 17.2% and 33.32%, respectively.