Support for Speculative Update Propagation and Mobility in Deno
Support for Speculative Update Propagation and Mobility in Deno
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Date
2000-07-11
Authors
Cetintemel, Ugur
Keleher, Peter J.
Franklin, Michael
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Abstract
This paper presents the transactional framework of Deno, an object
replication system specifically designed for use in mobile and
weakly-connected environments. Deno uses weighted voting for availability
and pair-wise, epidemic information flow for flexibility. This combination
allows the protocols to operate with less than full connectivity, to easily
adapt to changes in group member-ship, and to make few assumptions about the
underlying network topology. These features are all crucial to providing
effective support for mobile and weakly-connected platforms.
Deno has been implemented and runs on top of Linux and Windows NT/CE
platforms. We use the Deno prototype to characterize the performance of two
versions of Deno's protocol. The first ver-sion enables globally
serializable execution of update transactions. The second supports a weaker
consistency level that still guarantees transactionally consistent access to
replicated data. The re-sults show that our protocols either outperform or
perform comparably to existing approaches, while achieving higher
availability. Further, we show that the incremental cost of providing global
serializability in this environment is low. Finally, we show that commit
delays can be sig-nificantly decreased by allowing votes to be cast, and
votes and updates to be disseminated, speculatively.
(Also cross-referenced as UMIACS-TR-99-70)