File Creation Strategies in a Distributed Metadata File System

As computing breaches petascale limits both in processor performance and storage capacity, the only way that current and future gains in performance can be achieved is by increasing the parallelism of the system. Gains in storage performance remain low due to the use of traditional distributed file systems such as NFS, where although multiple clients can access files at the same time, only one node can serve files to the clients. New file systems that distribute load across multiple data servers are being developed; however, most implementations concentrate all the metadata load at a single server still. Distributing metadata load is important to accommodate growing numbers of more powerful clients. Scaling metadata performance is more complex than scaling raw I/O performance, and with distributed metadata the complexity increases further. In this paper we present strategies for file creation in distributed metadata file systems. Using the PVFS distributed file system as our testbed, we present designs that are able to reduce the message complexity of the create operation and increase performance. Compared to the basecase create protocol implemented in PVFS, our design delivers near constant operation latency as the system scales, does not degenerate under high contention situations, and increases throughput linearly as the number of metadata servers increase. The design schemes are applicable to any distributed file system implementation.