We recommend installing a software on your server to keep track of how much bandwidth you are using. There are many open source solutions available one of them is vnStat.
vnStat:
vnStat is a console-based network traffic monitor for Linux and BSD that keeps a log of network traffic for the selected interface. It uses the network interface statistics provided by the kernel as information source. This means that vnStat won’t actually be sniffing any traffic and also ensures light use of system resources.
Install:
Ubuntu/ Debian:
cd /usr/local/src
wget http://humdi.net/vnstat/vnstat-1.10.tar.gz
tar -zxvf vnstat-1.10.tar.gz
cd vnstat-1.10
make && make install
vnstat -u -i eth0
chmod 700 /usr/bin/vnstat
chmod 700 /var/lib/vnstat/ -R
http://www.dotcomunderground.com/blogs/2010/03/05/install-vnstat-network-traffic-monitor-linux/
CentOS:
