Exploiting Cross-Layer Hotness Identification to Improve Flash Memory System Performance

Flash memory has been widely deployed in modern storage systems. However, the density improvement and technology scaling would decrease its endurance and I/O performance, which motivates the search to improve flash performance and reduce cell wearing. Wearing reduction can be achieved by lowering the threshold voltages, but at the cost of slower reads. In this paper, the access hotness characteristics are exploited for read performance and endurance improvement. First, with the understanding of the reliability characteristics of flash memory, the relationship among flash cell wearing, read latency and bit error rate is introduced. Then, based on the hotness information provided by buffer management, the threshold voltages of a cell for write-hot data are decreased for wearing reduction, while these for read-hot data are increased for read latency reduction. We demonstrate analytically through simulation that the proposed technique achieves significant endurance and read performance improvements without sacrificing the write throughput performance.