Roam: a scalable replication system for mobile computing

Nomadic users require replication to store copies of critical data on their mobile machines while disconnected or poorly connected. Existing replication services do not provide all classes of mobile users with the capabilities they require, which include: the ability for direct synchronization between any two replicas, support for large numbers of replicas, and detailed control over what files reside on their local (mobile) replica. Mobile users must adapt their behavior to match the level of service provided by today's replication systems, thereby hindering mobility and costing additional time, money, and systems management. Roam is a replication system designed to satisfy the requirements of the mobile user. Roam is based on the Ward Model, a replication architecture for mobile environments. Using the Ward Model and new distributed algorithms, Roam provides a scalable replication solution for the mobile user. We describe the motivation, design, and implementation of Roam and report its performance.