A possible alternative to Glacier+product X (you mention Arq) could perhaps be Git-Annex, recently mentioned as it's Kickstarting a friendly UI component: http://news.ycombinator.com/item?id=4385886 http://www.kickstarter.com/projects/joeyh/git-annex-assistan...

Already has Amazon support: http://git-annex.branchable.com/tips/using_Amazon_S3/

Very friendly with very large files!