I used this very useful guide and I ran into an issue with downloading large files.
I only have an upstream of about 1Mb/s which results in a transfer time of about 9000 seconds (2.5h) for a 9Gb file. After about 4000 seconds however, it dies. It helped to increase request_terminate_timeout in /etc/php/7.0/fpm/pool.d/www.conf to (way) more than 9000 seconds (which was set to 3600 before I think). So that value should be adjusted according to your upstream (or downstream if this is your limiting factor) and the maximum file size.
You might want to add that to the guide.