Octopus: an RDMA-enabled Distributed Persistent Memory File System

Non-volatile memory (NVM) and remote direct memory access (RDMA) provide extremely high performance in storage and network hardware. However, existing distributed file systems strictly isolate file system and network layers, and the heavy layered software designs leave high-speed hardware under-exploited. In this paper, we propose an RDMA-enabled distributed persistent memory file system, Octopus, to redesign file system internal mechanisms by closely coupling NVM and RDMA features. For data operations, Octopus directly accesses a shared persistent memory pool to reduce memory copying overhead, and actively fetches and pushes data all in clients to re-balance the load between the server and network. For metadata operations, Octopus introduces self-identified RPC for immediate notification between file systems and networking, and an efficient distributed transaction mechanism for consistency. Evaluations show that Octopus achieves nearly the raw bandwidth for large I/Os and orders of magnitude better performance than existing distributed file systems.