Last update - problem solved
Well, I'm now successfuly backing up courses of 6 tot 7 GB. I'll do a quick write-up of what I did, for anyone stumbling upon this topic.
After reading this again (https://haydenjames.io/mysql-server-has-gone-away-error-solutions) I asked the hosting company to change the settings below (after verifying I wasn't doing anything obviously stupid):
- Wait-timeout: 600
- Net read read timeout: 120
- Net write timeout: 120
- innodb_log_file_size: 3 gb (20% of 16gb in innodb buffer pool size)
PHP
- Mysql.connect_timout: 610
- mysql.allow_persistent=1
- max_allowed_packet_size=4GB
Most of these values can be even higher, but it works like this. I would suggest to anyone trying this to work in small increments.
Thank you all for your help.