P-BMS: A Bad Block Management Scheme in Parallelized Flash Memory Storage Devices.

Flash memory is used as a main data storage medium in increasingly large areas of applications, rapidly replacing hard disk drives because of its low power consumption, fast random access, and high shock resistance. Such flash-based storage devices generally incorporate multiple flash memory chips to meet the ever growing capacity demands. Using multiple chips in a single storage device, at the same time, opens an opportunity to boost the performance based on multi-unit parallelism. However, parallel execution of multiple flash operations introduces complications when bad blocks occur, which is unavoidable due to flash memory’s physical characteristics. The situation gets even worse when bad block occurrences are accompanied by sudden power failures. We propose a bad block management scheme called P-BMS that can fully utilize flash-level parallelism, while guaranteeing provably correct block replacement. Experiments show that our P-BMS achieves a throughput that is more than 95% of the maximum bandwidth of the flash controller, even with bad block occurrences far heavier than in real flash memory.