I have 100+ machines which needs to be monitored, mostly linux, but there are some Windows servers too. I want to be informed when the disks are getting full, when the load is high, or a service is not responding, etc...
As I understand SNMP is not good, since it requires two way communication, and I do not want to open ports (and some of these machines are behind NAT-s and VPN-s).
What I want is: Install an agent to every machine. This agent sends info periodically to a central server. I show these data on the server, and send out notifications when something needs attention.
Is there any - opensource - tool to do this?