SARCNFS: Self-Adaptive Redundancy Clustered NAS File System

In this paper, we describe the design and implementation of SARCNFS File System for network-attached clustered storage system. SARCNFS stripes the data and metadata among multiple NAS nodes, and provides file redundancy scheme and synchronization mechanism for distributed RAID5. SARCNFS uses a self-adaptive redundancy scheme for file data accesses that uses RAID5-level for large writes, and RAID1-level for small write so as to dynamically provide flexible switch between RAID1 and RAID5 to provide the best performance. In addition, SARCNFS proposed a simple distributed locking mechanism that uses RAID5-level for full stripe writes, and RAID1-level for temporary storing data from partial stripe updates. As a result, low response latency, high performance and strong reliability are achieved.