ReoFS: A Read-Efficient and Write-Optimized File System for Persistent Memory

In this paper, we present ReoFS, a read-efficient and write-optimized PM-aware (Persistent Memory-Aware) file system that provides strong consistency guarantee. Different from traditional journaling techniques, ReoFS optimizes write requests on the write I/O path and allows concurrent reads to be served opportunistically. To reduce the write overhead for metadata-related operations, we devise a backup buffering mechanism, which keeps a replica of metadata in the backup buffer and supports fast in-place update. To minimize the write overhead for file data modifications, we design a fine-grained short logging mechanism to migrate writes to persistent log blocks and make new writes visible immediately after the log is persisted. With these two designs, ReoFS removes the double write overhead off the critical path of request execution for both metadata and data operations. We conduct extensive experiments on Intel Optane DC PM platform and the results show that ReoFS outperforms existing PM -aware file systems by 1.3x-4x.