Agent versus Agentless Monitoring

Like many other software packages, MOM and OpsMgr can deploy an agent to the system being monitored. Whether or not to deploy agents in general is always a discussion point. Let's talk about the agent used by Operations Manager.

While Operations Manager can use agentless monitoring, most management packs are built to perform better with an agent. The rules and other managment pack objects are deployed to each agent that they pertain to, allowing monitoring to occur even if contact is lost with the management server. Without an agent, the agent component on the management server collects data from the agentless managed computer using remote calls to that system. If the two systems cannot communicate, information is not collected.

In some cases, any change to a computer may lead to complications. While sometimes these complications are more political than operational, the IT group may want to avoid even the appearance of affecting an applicaiton server to avoid potential liability. Agentless sytems have a more limited set of features than do agent-based managed computers. Some mangement packs will not even run agentless. This list includes:

• Active Directory
• Exchange
• IIS
• SharePoint Portal Server

Other management packs such as SQL Server can run agentless but with reduced functionality.

For Operations Manager, agentless monitoring is recommended only when an agent-managed configuration is not possible. While agentless monitoring may decrease the load on the monitored system, it increases the resource load on the managment server monitoring that system. It also leads to increased network utilization when the data is sent across the pipe, is not as reliable in collecting data as using agent-monitored systems, and has reduced management capability.

For other discussions on agent-based vs. agentless in general, see http://www.networkworld.com/news/2007/102607-arguments-agent-based-agentless.html?nwwpkg=50arguments.