Just a quick notice about ProFTPd and TLS enabled.
If your version of it is "1.3.5", you probably have a know bug with "mod_tls" which seems to force the server to redo the certificate exchange with the client.
In short, all folder changes take in general 5 to 10 seconds.
Actually, Debian 8.1 is impacted as well as the latest Ubuntu stable version which didn't mention the fix in the changelog of the package.
Official fix has been applied in version 1.3.5a (and the actual testing version 1.3.6rc1).
The best way to fix this should be to recompile the whole ProFTPd application, or if you want to keep the version provided by your package manager, disable the TLS if this is too annoying for you.
The solution I use and nuxwin will not agree, and can agree with him too, is to compile the proftpd app, then get only the new "mod_tls.so" file which has the fix in it. It's a working solution for me at least, but I didn't recommend you this solution without further tests.