Funny how we differ. I truly think, seeing as you're the one doing a service for the client, you're responsible for the integrity and performance of his server. This also means his files. Get the free backup program called Cobian, it can upload via SFTP and the works. Backup the user folders from TCAFiles on every gameserver.
Also schedule backups in the off hours, say 5 am till finish, for me it usually takes about 2-3 hours for a full backup. This is 150gb uncompressed, but cobian can get it down to 40gb, incrementals are even lower.
Still, interesting to see the different standpoints on this.