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Agentless versus Agent-based server monitoring

Level 14

Monitoring servers, applications, networks and services is crucial. However, in today's datacenter, it's more complex than ever, with physical servers, virtual servers, cloud-based servers and legacy servers all running alongside one another.

The argument over agent-based versus agentless monitoring has been going on for quite a long time. Initially, the power, reliability, functionality, and all-around robustness of agent-based monitoring overwhelm the perceived advantages of lower cost, easier to implement/maintain features of agentless monitoring.

However, all this is changing with the need for organizations to be agile and the evident downside of agent based monitoring systems due to the complexity involved with agents.

Agent-Based Server Monitoring Hassles

  • Red Tape: The agent software runs on the remote machine and therefore affects its operation. In many environments, especially governments and larger corporations, you simply can't go installing software on critical machines without going through an evaluation and approval process.
  • Time to Maintain Agents:  Agents are very hard to maintain. As the monitoring solution is updated, the agents will need to be updated from time to time.
  • Scalability/Footprint:  Deploying, managing or administering, and monitoring connectivity with large numbers of clients and servers can become untenable. The problem is even more complicated when considering network infrastructure devices for which the number of possible connection paths is vast.

With all the hassles of agent-based monitoring, there are a few benefits which include deployment flexibility (eliminating NAT/Firewall/Proxy issues) as well as obtaining data such as event logs that are not obtained with agentless solutions.

Agentless Server Monitoring
Agentless monitoring is deployed in one of two ways:

Using a remote API exposed by the platform or service being monitored or directly analyzing network packets flowing between service components.

SNMP is typically used to monitor servers and network devices in an agentless manner. In the case of Windows servers, WMI (Windows Management Instrumentation) is typically used which provides a better set of metrics than can be obtained through SNMP monitoring alone.  Also for many Windows based servers and applications, agentless monitoring via the WMI gateway provides strong monitoring capabilities.

Agentless monitoring has certain distinctive advantages over monitoring with agents. Some are highlighted below:

• No Clients to deploy or maintain
• Lightweight, no application to install or run on the client. Typically consumes no additional resources
• WMI & VMware Agentless Monitoring is stronger than SNMP alone
• Typically lower initial cost for software

With all the various available options, it’s quite important to understand the business impacts in your particular environment for picking one server monitoring technology over another.

Related blog post: Customer spotlight: Agentless Enterprise Monitoring at Cardinal Health

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6 Comments
Level 15

insightful posting.  thanks!

Level 8

Just the write up I was looking for in my decision making process.

Level 14
MVP
MVP

I think it is great that Orion has gone full circle and embraces agents although the agentless they built their base on still required an agent.

The modern agents provide so much more in capability...  One thing not mentioned was store and forward.  With the real agent it would store polled metrics/events in the event of a communication failure and then forward them when the link was back up.  Thus you wouldn't have any gaps in your data whereas with the "agentless" if you lose communication, you just have a big black hole in time in your database.

Level 13

Agentless is my preferred method, but can't always get every bit of information I'm looking for.

Level 7

Nicely put. Both agent-based and agentless monitoring have their benefits:

1. In terms of Deployment: Agentless Monitoring is easier to deploy as compared to agent-based. In agent-based monitoring, agents need to be deployed on each server.

2. Network Overhead: Agentless monitoring requires additional network traffic as the raw performance data is transported to a remote data collector. Whereas agent-based monitoring is bandwidth efficient because data is collected locally.

Read more comparison details at http://www.appperfect.com/blog/agentless-vs-agent-based-monitoring.

In my opinion, choose according to the need and resources in hand. If you have enough bandwidth go for Agentless monitor, a suggestion http://www.appperfect.com/products/agentless-monitor.php.

About the Author
Like SolarWinds, I have roots in Oklahoma and have been fond of land grant schools as I went from Oklahoma State University, moving South to Texas A&M University.  Like my college career (accounting, political science, Russian language and then MBA), I have suffered ADD in my professional career moving from finance to strategy to product management and marketing.  I have, however, settled on the broad niche of systems management and have acquired knowledge in this space over the last 11 years. I was very happy to join the SolarWinds team in January 2012 and have been very impressed with the technology.  I look forward to engaging with this community.