If you turn on the log in /etc/vsftpd/vsftpd.conf then transfers are logged to /var/log/xferlog by default (the name can be changed too). [by TrevorH]
On my fresh Debian7 server, I have installed vsftpd server from official repo.
I am installing a new server and I have been adjusting my vsftpd settings when it suddenly stopped working. I noticed that the service vsftpd only worked if the vsftpd.conf while was empty or deleted.