OFWAR: Reducing SSD Response Time Using On-Demand Fast-Write-and-Rewrite

This paper presents a cross-layer design strategy to reduce SSD response time and its variation. The key is to cohesively exploit system-level run-time data access workload variation and temporal locality and device-level NAND flash memory write latency versus data retention time trade-off. The basic idea is simple: once write intensity of the workload increases and begins to degrade SSD response time, we speed up memory programming at the penalty of shorter data retention time, and rewrite these short-lifetime data later, if necessary, when workload write intensity drops. A scheduling solution is developed to effectively implement this design strategy. Simulations over various workloads were carried out and the results demonstrate that the cross-layer design strategy can reduce the average SSD response time by up to 52.3%.