Communications and consistency in mobile file systems

To overcome the availability, latency, bandwidth, and cost barriers of mobile networks, mobile clients of distributed file systems switch between connected and disconnected modes of operation. Lying between these are modes of operation that refine the consistency semantics of cached files, allowing a mobile client to select a mode appropriate for the prevailing network conditions. Clients can take advantage of network opportunities unsuitable for connected operation, obtaining improved performance, more effective sharing, and more stringent consistency guarantees as a result. Today's mobile computing technology lets nomadic users operate computers large and small from their offices and homes and places in between. However, mobile users are often frustrated by the quality of distributed services available to them. In this article, we describe ways to extend the advantages of distributed file systems to users of mobile computers.