Enhancing the energy efficiency of journaling file system via exploiting multi-write modes on MLC NVRAM

Non-volatile random-access memory (NVRAM) is regarded as a great alternative storage medium owing to its attractive features, including low idle energy consumption, byte addressability, and short read/write latency. In addition, multi-level-cell (MLC) NVRAM has also been proposed to provide higher bit density. However, MLC NVRAM has lower energy efficiency and longer write latency when compared with single-level-cell (SLC) NVRAM. These drawbacks could lead to higher energy consumption of MLC NVRAM-based storage systems. The energy consumption is 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 a multi-write-mode journaling file systems (mwJFS) to alleviate the drawbacks of MLC NVRAM and lower the energy consumption of MLC NVRAM-based JFS. The proposed mwJFS differentiates the data retention requirement of journaled data and applies different write modes to enhance the energy efficiency with better access performance. A series of experiments was conducted to demonstrate the capability of mwJFS on a MLC NVRAM-based storage system.