Remote access to distributed file systems.

Abstract

Technological trends such as the availability of mobile computers and the expanding network infrastructure are creating a large number of users who access distributed file systems remotely. Remote access differs from normal access because of differences in the network quality. In the office, clients use high bandwidth, low latency networks, but the remote environment is typically composed of low bandwidth; high latency networks. Additionally, remote networks are intermittently available. Accessing distributed files in the remote environment is difficult because most distributed file systems are designed with the office environment in mind. Without a network, files are inaccessible. When a network is available, file system performance, suffers because of the network latencies incurred by many files system operations. This thesis describes how remote access to distributed files can be improved by relaxing file system guarantees, including freshness of data and immediate propagation of file modifications. Relaxing these guarantees reduces or eliminates network demands. This allows clients to adjust file system behavior to match the available network. A prototype of these changes is implemented using AFS. The resulting file system allows file access when networks are unavailable and substantially improves performance over low bandwidth networks.