Historic:Bitcloud style
Butcloud is a A Decentralized Application for Cloud Services Based on Proof of Bandwidth.
https://github.com/wetube/bitcloud/blob/master/Bitcloud%20Nontechnical%20White%20Paper.md
it looks very promising, but is not implemented yet. Maybe we should keep that option in mind and design our architecure in a way so that it will be possible to move to bitcloud in case if it becomes available in the future.