“Monitoring of your computer systems is a good idea. There are many tools that let you verify that specified services are running, and available for clients. I use Nagios. You can check that Apache is still running, Postfix is still accepting mail, and various other things. If you can write a test, Nagios can monitor it.
Typically, people monitor network connections, applications, and bandwidth consumption. Until recently, I did not monitor disk health. That recently changed.
I started using three new tools:
In this article I’ll show you how I added SMART monitoring to my Nagios installation. munin is straight forward to install, but is outside the scope of this article. It is for another time.
This article also assumes you have Nagios installed and nrpe running on the host you are monitoring. I am using Fruity for my nagios configuration, so I will be glossing over that too.”
Go to the howto (FreeBSD Diary)