RESEARCHERS DEVELOP SOFTWARE FOR SYNCHRONIZING
FILES ON MULTIPLE COMPUTERS AND DISTRIBUTE IT FREE ONLINE
PHILADELPHIA - Responding to the burgeoning population of
computer users now working on more than one machine, University
of Pennsylvania researchers have developed software that can
keep replicated files consistent across multiple computers.
Their program, dubbed Unison, can be downloaded from www.cis.upenn.edu/~bcpierce/unison.
"Ten years ago, only a handful of people used more than
one computer," says Benjamin Pierce, Ph.D., Unison's
lead developer and an associate professor of computer and
information science at Penn. "Now it's commonplace. Many
professionals have both a laptop and a desktop computer at
work and frequently also a third machine at home."
With this explosion in the number of people juggling multiple
computers has come the need for so-called file synchronization
software, capable of maintaining consistency between copies
of files on different computers' hard drives. When confronted
with two machines, each housing a set of common files, Unison
selects the newest version of each file and saves it on both
hard drives, replacing outdated versions.
After revising a document on one machine, consumers can use
Unison to automatically propagate the changes to their other
computers as well. For instance, a frazzled undergraduate
alternating between a laptop and a dorm-room desktop while
writing a series of term papers can let Unison do the dirty
work of ensuring that each machine has the same - and the
most recent - drafts saved on its hard drive.
"Since the hard drives on computers have gotten so huge,
people are tempted to keep copies of all their files on all
their machines," Dr. Pierce says. "But this creates
a logistical nightmare, trying to figure out which computer
has the most up-to-date version of which file. Unison solves
that problem."
While similar tools have been built in the past, Unison has
distinct advantages over other file synchronizers now on the
market. It works on both Windows and Unix systems and can
even work between two computers running different operating
systems, synchronizing a Windows laptop with a Unix server,
for instance.
Moreover, unlike other file synchronization software that
can sell for several hundred dollars, Unison is an open-source
project: it's freely downloadable and comes with source code
that users can modify if they wish.
Unison is also highly resistant to the myriad disruptions
faced by computer users.
"A synchronizer is an extremely 'intimate' tool: it
messes with all of your precious files, and if it makes a
mistake it may be months before you notice," Dr. Pierce
says. "Unison can be interrupted at any point in its
work - by a network failure, a machine crash, the user popping
out the modem card and running for the airport - and leave
both machines in a clean and sensible state."
Unison also comes with a clear and precise specification
of its behavior, both in the form of extensive documentation
and in the form of a mathematical specification that users
can read to understand its behavior in all cases.
In addition to Dr. Pierce, Unison's development team included
graduate student Sylvain Gommier, postdoctoral researcher
Dr. Jerome Vouillon and Dr. Trevor Jim of AT&T Laboratories.
The work was supported in part by the National Science Foundation.
|
