Effective Lifetime-Aware Dynamic Throttling for NAND Flash-Based SSDs

NAND flash-based solid-state drives (SSDs) are increasingly popular in enterprise server systems because of their advantages over hard disk drives such as higher performance and lower power consumption. However, the decreasing write endurance and the unpredictable lifetime remains to be a serious obstacle to their wider adoption in enterprise systems. In this paper, we propose effective lifetime-aware dynamic throttling, called LADY, which guarantees the required storage lifetime by intentionally throttling the write performance of SSDs with consideration of the effective write endurance of NAND flash memory. Unlike existing static throttling, LADY makes throttling decisions based on the characteristics of a workload so that the required SSD lifetime can be guaranteed with less performance degradation. LADY also exploits the improvement on write endurance depending on the NAND program speed and the recovery effects of floating-gate transistors, thereby maximally utilizing the available write endurance of NAND flash while mitigating the decreasing write endurance problem. Our experimental results show that LADY improves write performance by 4.7x with small write response time variations over existing static throttling while guaranteeing the required SSD lifetime.