I have a network of disparate remote VPS / "cloud" / colocated servers that I would like to monitor from a central location, using open source software like Zenoss/Zabbix/Nagios/OpenNMS/Opsview/Observium etc... These servers are not necessarily physically located near each other. I have a core network of servers on a reasonably fast circuit, one of which will collect the data.
I need to minimize the load on the remote servers as much as possible (some are small 256MB webservers, for instance) , so I am looking for the solution that presents the remote agent that consumes the least resources.
I would like to be able to monitor processes/network usage/logs/mail queues etc. on each device.
Given my restrictions and architecture, is there a specific product (open source) that you would recommend?
Nagios NRPE is very light weight.
The consumption of resources from the servers depends mostly on the checks you run. Each check is an executable on the client.
Basic checks are not heavy. I run Nagios without problems and also on very small VPS nodes.