Wonho Kim will present his preFPO on Friday December 16 at 4PM in Room 402. The members of his committee are: Vivek Pai, advisor; Larry Peterson and Michael Freedman, readers; Jennifer Rexford and David Walker, nonreaders. Everyone is invited to attend his talk. His abstract follows below. ---------------------- Title: Understanding Resource Usage and Performance in Wide-area Distributed Systems Many Internet services employ wide-area frameworks to deliver exponentially growing network traffic to end-users with low response time. These systems typically leverage a large number of servers distributed to the edges of the Internet, which makes the systems difficult to design and manage. In this thesis, we examine resource usage and the performance of remote synchronization in wide-area systems. To support the development of new network services on a global scale, the next generation of federated testbeds are under active development, but very little is known about resource usage in the shared infrastructures. We conduct an extensive study of the usage profiles in PlanetLab that we collected for six years by running CoMon, a PlanetLab monitoring service. We examine various aspects of node-level behavior as well as experiment-centric behavior, and describe their implications for resource management in the federated testbeds. We find that the usage is much different from shared compute clusters, that conventional wisdom does not hold for PlanetLab, and that several properties of PlanetLab as a network testbed are largely responsible for this difference. We also present a latency-sensitive file synchronizer, Lsync, that can be used as synchronization building block for wide-are distributed systems where latency matters. While many distributed systems depend on fast data synchronization for coordinating remote nodes, current data dissemination systems focus on efficiency for open client populations, rather than focusing on completion latency for a known set of nodes. In examining this problem, we find that optimizing for latency produces strategies radically different from existing distribution tools, and can dramatically reduce latency across a wide range of scenarios. Lsync performs novel node selection, scheduling, and adaptive policy switching that dynamically chooses the best synchronization method using information available at runtime. Our evaluation results show that Lsync reduces latency by more than a factor of 14 compared to a widely used synchronization tool, and makes most remote nodes fully synchronized even under frequent file updates.