Abstract

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 systems.

Our measurements of a Fluid Replication prototype show that update performance is completely independent of wide-area networking costs, at the expense of increased sharing costs. This places the costs of sharing on those who require it, pre-serving common case performance. Furthermore, the benefits of independent update outweigh the costs of sharing for a work load with substantial sharing. A trace-based simulation shows that a modest reconciliation interval of 15 seconds can eliminate 98% of all stale accesses. Furthermore, our traced clients could collectively expect availability of five nines, even with deferred propagation of updates.

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