Need some advice for setting up cloud storage.

I have to set up some cloud storage, and I was thinking about using some rPi's with a few 4TB HDD's each spread across a few continents. The use case is basically several TB of large, mostly-unchanging files backed up by a ton of cheap and redundant nodes for only a small group of users (<10).

Swift seems like the best option for my needs, but I'm not sure that the Pi's are powerful enough to run it. Other options are Ceph and Gluster. My biggest needs are decentralization, resiliency for hardware failures, and data integrity. Object-storage seems to be the best fit for the criteria, but I haven't done this before and I'd like some input from People With Experience(tm).

(Tahoe-LAFS seemed like a great option, but I can't even consider it until they support multiple introducers, which is planned for 1.11 IIRC)