How to limit virtual host bandwidth

[姜文栋]

I want to run a web hosting, and I want to limit every virtual host bandwidth as a whole (No need limit_conn*limit_rate), how? 

If can't, how to limit client connection and server connection number at the same time, like this:
    limit_zone client_conn $binary_remote_addr 10m;
    limit_conn client_conn 20;
    limit_zone server_conn $server_name 10m;
    limit_conn server_conn 100;
This is invalide in nginx config, how to make it work?