Thank you very much for the detailed explanation of how to add Amazon S3 backup capability to Retrospect! I followed your method to the letter and I too now have my home PC backing up via TNTDrive to my personal AWS account. I had tried other cloud storage vendors via Webdav but this never really worked for me mainly because of the slow upload speeds caused by the distant locations of the cloud vendor's servers. With Amazon, I am able to select a server near my location so upload speeds are pretty good even via the VDSL broadband connection that I have in my apartment.
Since this worked so well, I have now signed up for an AWS account at my work place, and am going to do some trials with backing up from my Retrospect Multi-Server 10 set up at work. Hopefully, the faster broadband connection at my work will let me get some good backup speeds compared to my home.
Thanks again for the detailed how-to.