hUBI: An Optimized Hybrid Mapping Scheme for NAND Flash-Based SSDs

NAND flash-based SSDs have become attractive alternatives to hard disk drivers due to their high random read performances and low power consumptions. However, the poor random write performances highly limit their popularization in commercial applications. In this paper, we propose a novel mapping scheme called hybrid mapping unsorted block images (hUBI). hUBI aims for (1) optimized random write performances, (2) low write latencies, and (3) low space consumptions. It optimizes traditional hybrid mapping schemes to achieve (1). In hUBI, the merge operation involves only a single block. So, (2) is guaranteed. To avoid introducing a high space cost maintaining the metadata, hUBI puts its metadata into out-of-band (OOB) areas of SSD pages, which obtains (3). Our experimental results show that hUBI provides a considerable random write performance and holds low write latencies at the same time.