The Geek Stuff posted a guide about installing Zenoss Core for Monitoring on Linux CentOS / RHEL
Zenoss is an open source agentless monitoring tool.How to Install Zenoss Core for Monitoring on Linux CentOS / RHEL
The main advantage of zenoss is that you don’t need to install any software on the client side for monitoring.
Zenoss has the following two versions:
Zenoss Core (this is free)
Zenoss Enterprise. This is also called as Zenoss Resource Manager, which is a paid version. This provides several additional features: High-availability, distributed architecture, event correlation, etc.