Safety, Visibility, and Performance in a Wide-Area File System

As mobile clients travel, their costs to reach home filing services change, with serious performance implications. Current file systems mask these performance problems by reducing the safety of updates, their visibility, or both. This is the result of combining the propagation and notification of updates from clients to servers. Fluid Replication separates these mechanisms. Client updates are shipped to nearby replicas, called WayStations, rather than remote servers, providing inexpensive safety. WayStations and servers periodically exchange knowledge of updates through reconciliation, providing a tight bound on the time until updates are visible. Reconciliation is non-blocking, and update contents are not propagated immediately; propagation is deferred to take advantage of the low incidence of sharing in file