S3 with RRS would be better, but the economics may not work out. However, unlike normal internet based backups, you can't replace corrupted / lost files sneakil

S3 with RRS would be better, but the economics may not work out. However, unlike normal internet based backups, you can't replace corrupted / lost files sneakily, well not until the next backup-drive arrives. Also, be aware that you'll not be able to de-dupe files across users (this also has issues if you could) as you're encrypted. Also, if the encryption key is different, you won't even be able to do this cross backups...which will suck.