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I have a TrueCrypt container (around 50GB) which has all of my backups inside. I'd like to back up the container to cloud storage (not the files within), but obviously, I'd prefer not to re-upload 50GB every time a change is made to the container. What would be the best cloud storage service for this scenario? Ideally, I'm looking for a service with block-level updates and doesn't filesync (i.e. not dropbox, which incidentally does have block-level updates).