[talks] W Kim preFPO

[Melissa M. Lawson]

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.
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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.