So, from what I understand, this is great but more of a proof of concept since fuse performance kills it. As far as putting it in production, there are a few unresolved questions which I haven't seen picked apart:

- Can dedup be integrated into the VFS layer, like unionfs is shooting for, or does it have be integrated with the underlying filesystem.

- Is online dedup possible, and does the answer change when running SSD.

- What's the best granularity (block-level? inode-level? block extent-level?) and how badly can it randomize the i/o. I imagine one would have to do a lot of real-world benchmarking to find this out.

- Are there possible privacy issues (i.e. finding through i/o patterns whether someone else has a given block or file stored) and how to deal with them