DPLFS: A Dual-Mode Phase Change Memory Based Log-Structured File System

With the development of computer technology,the performance of storage system becomes the major bottleneck of computer system.Emerging no-volatile memories(NVM)such as phase change memory(PCM)promise to solve this problem.How to take full advantage of NVM's high performance and improve throughput of storage system without sacrificing data consistency,has been an important topic in the field of computer architecture.Therefore,a dual-mode PCM based log-structured file system(DPLFS)is proposed to optimize for features of dual-mode device,which alleviates the problem of MLC's write performance,and effectively improves throughput of storage system.DPLFS keeps file data in MLC(Multi-Level Cell)devices,and metadata in SLC(Single-Level Cell)devices.SLC devices are used as write buffers of the file system,and files are written back to MLC in the way of XOR when there is insufficient available space in SLC,which improves write performance of the file system.To speed up directory search,directory files are stored in SLC.Simultaneously,related optimization efforts are made in DPLFS,which uses PCM for persistent storage,DRAM for accelerating data retrieval,and utilize log-structured technology to ensure data consistency.A system prototype of DPLFS is implemented in the Linux kernel version 4.3.Experimental results show that,DPLFS has a noticeable performance improvement relative to traditional log-structured file systems NILFS2 and F2 FS.Compared to journaling file system Ext4 and shadow paging file system Btrfs,DPLFS improves performance by 2.5 times on average,while providing the same data consistency.DPLFS provides a better performance than NOVA,the state-of-the-art research production in his field,especially for write performance.The system throughput of DPLFS improves 21%and 11% in write intensive and read intensive workloads respectively compared to NOVA.