Thesis Defense: Flexible, Wide-Area Storage for Distributed Systems Using Semantic Cues
Speaker: Jeremy Stribling , MIT CSAIL
Date: August 6 2009
Time: 1:00PM to 2:00PM
Location: G449 (Patil/Kiva)
Host: M. Frans Kaashoek, MIT CSAIL
Contact: Jeremy Stribling, strib@mit.edu
Relevant URL: http://pdos.csail.mit.edu/wheelfsAbstract:
There is a growing set of Internet-based services that are too big, or
too important, to run at a single site. Examples include Web services
for e-mail, video and image hosting, and social networking. Splitting
such services over multiple sites can increase capacity, improve fault
tolerance, and reduce network delays to clients. These services often
need storage infrastructure to share data among the sites. This
talk explores the use of a new file system (WheelFS)
specifically designed to be the storage infrastructure for wide-area
distributed services.
WheelFS allows applications to adjust the semantics of their data
via semantic cues, which provide application control over
consistency, failure handling, and file and replica placement. This
talk describes a particular set of semantic cues that reflect
the specific challenges that storing data over the wide-area network
entails: high-latency and low-bandwidth links, coupled with increased
node and link failures, when compared to local-area networks. By
augmenting a familiar POSIX interface with support for semantic cues,
WheelFS provides a wide-area distributed storage system intended to
help multi-site applications share data and gain fault tolerance, in
the form of a distributed file system. Its design allows applications
to adjust the tradeoff between prompt visibility of updates from other
sites and the ability for sites to operate independently despite
failures and long delays.
WheelFS is implemented as a user-level file system and is deployed on
PlanetLab and Emulab. Six applications (an all-pairs-pings script, a
distributed Web cache, an email service, large file distribution,
distributed compilation, and protein sequence alignment software)
demonstrate that WheelFS's file system interface simplifies
construction of distributed applications by allowing reuse of existing
software. These applications would perform poorly with the strict
semantics implied by a traditional file system interface, but by
providing cues to WheelFS they are able to achieve good
performance. Measurements show that applications built on WheelFS
deliver comparable performance to services such as CoralCDN and
BitTorrent that use specialized wide-area storage systems.
Thesis Advisors: M. Frans Kaashoek, Robert Morris, Jinyang Li (NYU)
Thesis Committee: Sam Madden
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