Looking software like dropbox but to install on my server [on hold]

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http://stackoverflow.com – I am looking software exatly like dropbox, but i want install that on my server, because of security reason. I have important data and i don't want anybody to read that data. Also i am working with team on same IT projects, so i need share folders between other users. Something like open source dropbox exist? It has to work good, without bugs and with good performance. Any alternative to do this on own server with similar quality? (HowTos)