If that's all the '662 patent is about is using hashes to deduplicate data then it should be invalid. I know I used this approach with MD5 as far back as October of 2001, and it was suggested by a co-worker who claimed to have done something similar 5 years prior.
Posted Sep 19, 2012 3:24 UTC (Wed) by Cyberax (✭ supporter ✭, #52523)
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"Fossil" fileserver on top of "venti" filesystem did this in Plan9 in 1993. And the idea itself is even more ancient.
Time to search for prior art
Posted Sep 27, 2012 12:26 UTC (Thu) by njs (guest, #40338)
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The idea was sufficiently well known for Val Henson (now Val Aurora) to publish a paper arguing against it in May 2003; she cites 6 different earlier systems using it: http://valerieaurora.org/review/hash/node2.html
The oldest appears to be rsync, with Tridge's thesis coming out in 1999, and for de-duplication specifically I'd check the paper on a backup system called "Pastiche" that was formally published in 2002...