I'm testing Opendedup, it seems to run correctly, but the real size of the files that I've put in the deduplicated partition is almost the same than the effectively size taken by this partition.
In the configuration file, deduplication is activated (dedup-files="true"), and it's indicated in the doc that it's activated by default, but I've only 130ko of duplicate bytes.
Data are video files, I guess I could gain more storage space.
edit
I've tested with a file filled with zeros, and the gain is better: 262ko for 1Mo. But if I gzip this file, I get 10ko, so I'd like to know if I can put option to get a better compression factor.
Video and zipped files don't dedupe well unless they are exactly the same. This is because within these files the data is very random and in the case of video data unique to the file in question.