The recent proliferation of portable computers, the introduction of a variety of pocket-sized computing devices and the rapid expansion of computer networks provide great promise for a future in which mobility of both users and computers will be standard. However, these developments also invalidate many of the assumptions made by current system software, which was designed for stationary systems and users. An important component of system software that needs redesign for mobility is the file system. Ideally, a user should be able to access the files he or she needs regardless of location. Although existing distributed file systems such as Coda provide a partial solution by supporting disconnected operation of clients, significant deficiencies remain. For example, the distributed file system is unavailable at isolated computers. We argue that the limited availability results from the strict client-server model used and propose a looser model.

A design based on this relaxed model is proposed. It utilizes a _persona carrier_, a computer that accompanies its owner at all times, as the bridge between isolated computers and servers. The persona carrier acts as a regular client when connected, hoarding files from servers. When disconnected, it may be used independently or as a pseudo-server to another isolated computer, providing it with needed files and recording any updates made there. Upon reconnection, the persona carrier propagates these updates to the servers.

A prototype implementation has been constructed for the Unix platform. We are considering porting the implementation to the NT platform. This would enable a performance comparison with respect to mobile systems between the Unix and NT filesystems.

Alan G. Yoder
Distributed Computing Research Laboratory
384 Fitzpatrick
Department of Computer Science and Engineering
University of Notre Dame
Notre Dame, IN 46556

phone (219) 631-5273
fax (219) 631-9260
email agy@cse.nd.edu
www https://www.nd.edu/~dcrlab