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pNFS/PVFS2 over InfiniBand: early experiences

The computing power of clusters has been rapidly growing up towards petascale capability, which requires petascale I/O systems to provide data in a sustained high-throughput manner. Network File System (NFS), a ubiquitous standard used in most existing clusters, has shown performance bottleneck associated with the single server model. pNFS, a parallel version of NFS, has been proposed in this context to eliminate the performance bottleneck while maintain the ease of management and interoperability features of NFS. With InfiniBand being one of the most popular high speed networks for clusters, whether pNFS can pick up the advantages of InfiniBand is an interesting and important question. It is also important to quantify and understand the potential benefits of using pNFS compared with the single server NFS, and the possible overhead associated with pNFS. However, since pNFS is relatively new, few such study has been carried out in an InfiniBand cluster environment. In this paper we have designed and carried out a set of experiments to study the performance and scalability of pNFS, using PVFS2 as the backend file system. The aim is to understand the characteristics of pNFS, and its feasibility as the parallel file system solution for clusters. From our experimental results we observer that pNFS can take advantages of high speed networks such as InfiniBand, and achieve up to 480% improvement in throughput compared with using GigE as the transport. pNFS can eliminate the single server bottleneck associated with NFS. pNFS/PVFS2 shows significantly higher throughput and better scalability compared with NFS/PVFS2. pNFS/PVFS2 achieves peak write throughput about 490MB/s, and read throughput about 2250MB/s, with 4 I/O servers. With 8 I/O servers, the numbers are 754MB/s and 3100MB/s. Further, we find that pNFS adds little overhead and achieves almost the same throughput as the backend file system PVFS2. Our results indicate that pNFS is promising as the parallel file system solution for clusters.