A Reliability-Aware Address Mapping Strategy for NAND Flash Memory Storage Systems

The increasing density of NAND flash memory leads to a dramatic increase in the bit error rate of flash, which greatly reduces the ability of error correcting codes (ECC) to handle multibit errors. NAND flash memory is normally used to store the file system metadata and page mapping information. Thus, a broken physical page containing metadata may cause an unintended and severe change in functionality of the entire flash. This paper presents Meta-Cure, a novel hardware and file system interface that transparently protects metadata in the presence of multibit faults. Meta-Cure exploits built-in ECC and replication in order to protect pages containing critical data, such as file system metadata. Redundant pairs are formed at run time and distributed to different physical pages to protect against failures. Meta-Cure requires no changes to the file system, on-chip hierarchy, or hardware implementation of flash memory chip. We evaluate Meta-Cure under a real-embedded platform using a variety of I/O traces. The evaluation platform adopts dual ARM Cortex A9 processor cores with 64 Gb NAND flash memory. We have evaluated the effectiveness of Meta-Cure on the new technology file system file system. Experimental results show that the proposed technique can reduce uncorrectable page errors by 70.38% with less than 7.86% time overhead in comparison with conventional error correction techniques.