ZFS + OpenSolaris
Greenbyte is using ZFS for their storage. ZFS has a deduplication functionality that is lacking in performance, so Greenbyte has rewritten the ZFS dedup engine. It would be really cool if Greenbyte would release their dedup engine into the open source ZFS world, but that will not happen I am afraid. But it would be wicked cool and make ZFS even better.
Competition is always good for us customers, I hope they succeed in putting pressure on the competitors so prices will be lowered.