Two-level logging with non-volatile byte-addressable memory in log-structured file systems

The file system durability is provided by flushing dirty pages periodically into the non-volatile storage. Since the traditional storage devices such as hard disk and flash memory can be written in the unit of block, the file system writes a whole block even when only a small number of bytes are modified. To resolve such a wasting write traffic problem, we propose a two-level logging scheme by exploiting non-volatile and byte-addressable memories (NVMs). Whereas the previous approach which exploits the NVM device is targeted for EXT4 file system, our scheme uses log-structured file systems in order to guarantee the file system reliability even for sudden system crashes. While the NVM is used for fine-grained logging, the flash memory is used for coarse-grained logging. Experiments with a real NVM device show that the proposed scheme reduces the write traffic on storage by up to 78% and improves the I/O performance significantly.