mwJFS: A Multiwrite-Mode Journaling File System for MLC NVRAM Storages

At present, nonvolatile random access memory (NVRAM) is widely considered as a promising candidate for the next-generation storage medium due to its appealing characteristics, including short read/write latency, byte addressability, and low idle energy consumption. In addition, to provide a higher bit density, multilevel-cell (MLC) NVRAM has also been proposed. Nevertheless, when compared with conventional single-level-cell (SLC) NVRAM, MLC NVRAM has longer write latency and higher energy consumption. Hence, the performance of MLC NVRAM-based storage systems could be degraded due to the lengthened write latency. The performance degradation is further magnified by existing journaling file systems (JFS) on MLC NVRAM-based storage devices due to the JFS's fail-safe policy of writing the same data twice. Such observations motivate us to propose multiwrite-mode JFSs (mwJFSs) to alleviate the drawbacks of MLC NVRAM and boost the performance of MLC NVRAM-based JFS. The proposed mwJFS differentiates the data retention requirement of journaled data and applies different write modes to enhance the access performance with lower energy consumption. A series of experiments was conducted to demonstrate the capability of mwJFS on MLC NVRAM-based storage systems.