i have a website that runs on two linux webservers and one linux db server. i would like to monitor all three of these servers to check load, uptime, etc. what is the simplest way to do this? i have heard that nagios is a good program. would i run this off of one server to monitor all three? or would i need to install this on all three servers? also, what happens if the server that is doing the monitoring ends up going down?