A synchronous file server for distributed file systems

Abstract

There is currently an enormous performance differential, as much as a factor of ten, between the write performance of local file systems and that of distributed file systems, such as the popular NFS [1]. Moreover, the underlying cause of this performance gap is such that as disks with faster transfer rates, or as multiple disks in parallel, are used, this performance differential can only increase. The performance differential is often attributed to the stateless nature of the distributed file system protocol, and many stateful protocols have been developed, partly justified by the increased file system write performance that results. Stateful protocols, however, are considerably more complex than stateless ones, and should be avoided if possible. The poor write performance of distributed file systems is actually due to a mismatch between the stateless file system protocols, which require the file system to be written synchronously, and current file system designs, which perform very poorly at writing synchronously. This mismatch can be rectified either by changing to stateful protocols, or by developing file systems that are good at writing synchronously. This paper describes the design of the Acacia synchronous file system, and analyses the performance of a prototype, user-level server implementation. The prototype’s performance already exceeds that of NFS, and detailed analysis of its performance indicates that further development will result in write performance similar to that of existing local file systems. Show more