Nagios (http://www.nagios.org) is a great network monitoring tool. Cacti (http://www.cacti.net) is a great network graphing tool. Perfparse (http://perfparse.sourceforge.net/ is a great add-on to Nagios that collects host performance data as part of the Nagios check command. Perfparse is great at collecting performance data when you are running Nagios client software, but short of doing a [...]