<p>I search an implementation of a network (or distributed) file system like NFS in Java. The goal is to extend it and do some research stuff with it. On the web I found some implementation e.g. <a href="http://users.csc.calpoly.edu/~jbergami/projects/djnfs/" rel="noreferrer">DJ NFS</a>, but the open question is how mature and fast they are.</p>

<p>Can anyone purpose a good starting point, has anyone experience with such things?</p>

<p>P.S. I know Hadoop DFS and I used it for some projects, but Hadoop is not a good fit for the things I want to do here. </p>

<p>--EDIT--
Hadoop is really focused on highly scalable, high throughput computing without the possibilities to overwrite parts of a file and so an. The goal is you could use the filesystem e.g. for user home directories.</p>

<p>--EDIT--
More Details: The idea is to modify such a implementation so that the files are not stored directly on a local filesystem, but to apply data de-duplication.</p>

I can't say I've actually played with anything other than HDFS, but here are some links that might help you.
http://www.hirednetwork.com/?p=61
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1266109
http://wiki.apache.org/nutch/NutchDistributedFileSystem