We have improved the publicly available statistics for our FTP server. You can now see how much traffic each individual mirror makes, and how much of the traffic was IPv6 vs. IPv4. The statistics are available at https://ftp.fau.de/cgi-bin/show-ftp-stats.cgi.
With this, you can see for example that the latest OpenSuSE 13.1 release had a quite significant impact on our FTP: The statistics for 19. November 2013 show that we distributed almost 9 TB for opensuse on that day, more than 5 times the traffic of all other mirrors combined.