mwm@VIOLET.BERKELEY.EDU (Mike Meyer, Take a giant step oustide your min) (12/24/86)
The following is the abstract for a recent paper on replicated
file systems. It will be presented at the Sixth Symposium on Re-
liability in Distributed Software and Database Systems, on March
17, 1987 in Williamsburg Virginia. A preliminary version is
available now in technical report form.
If you are interested in obtaining a copy, address inquires to:
Technical Report Librarian
Department of Electrical Engineering & Computer Science, C-014
University of Calfornia, San Diego
La Jolla, CA 92093
The cost is $2.00
DL
Darrell Long
Department of Electrical Engineering and Computer Science, C-014
University of California, San Diego
La Jolla, California 92093
ARPA: Darrell@Beowulf.UCSD.EDU
UUCP: sdcsvax!beowulf!darrell
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On Improving the Availability of Replicated Files
Darrell D. E. Long
Jehan-Francois Paris
Computer Systems Research Group
Department of Electrical Engineering and Computer Science
University of California, San Diego
La Jolla, California 92093
Technical Report CS-089
ABSTRACT
To improve the availability and reliability of
files the data are often replicated at several
sites. A scheme must then be chosen to maintain
the consistency of the file contents in the pres-
ence of site failures. The most commonly used
scheme is voting. Voting is popular because it is
simple and robust: voting schemes do not depend on
any sophisticated message passing scheme and are
unaffected by network partitions.
When network partitions cannot occur, better
availabilities and reliabilities can be achieved
with the available copy scheme. This scheme is
somewhat more complex than voting as the recovery
algorithm invoked after a failure of all sites has
to know which site failed last. We present in
this paper a new method aimed at finding this
site. It consists of recording those sites which
received the most recent update; this information
can then be used to determine which site holds the
most recent version of the file upon site
recovery. Our approach does not require any moni-
toring of site failures and so has a much lower
overhead than other methods.
We also derive, under standard Markovian
assumptions, closed-form expressions for the avai-
lability of replicated files managed by voting,
available copy and a naive scheme that does not
keep track of the last copy to fail.