This might be material for an article at the end, but we have (customers with) a need to have a good overview of the Pro's and Con's of having Virtual agents over Physical agent devices. Maybe I am overlooking an already existing page, but I did not find it here.
I can come up with several, and obvious, benefits and penalties, but I would like to have it as true and complete as possible. This so it can be used with business case discussions.
Virtual Vs. Physical: Enterprise Synthetic Agents
The obvious benefit of virtual systems is perhaps the cost aspect, you do not need to buy and maintain hardware for every agent, and replace it after so many years. The speed and virtual limitless amount of new deployments, worldwide, are some of the other. Increasing system resources is much easier as well.
The restrictions however lay in the dependency of a virtualization server platform on site, which limits the flexibility in choosing the workplace to monitor from, and perhaps the dependency of other teams to maintain your agent's availability. Plus there is the question of how representative are the measurements from a virtual DC system to that of the actual End User Experience, measured by a standard workplace system in office LAN environment. Which may draw different measurements, than a virtual machine (VM) in a steady data-center environment.
Here are from the perspective of Virtual Agents over Physical agents, the following Pro's an Con's I can think of:
Maintenance and Infrastructure
There may also be differences in capacity, the amount of transactions that can be run in a certain timeframe, before the system or the network connection becomes saturated. But in both cases this can be addressed by expansion, where a VM in general of course is easier to be expanded, but until certain limitations.
There are benefits to follow a heterogeneous approach, and inter mix physical with virtual agents, in both datacenters as user lan area's. Measuring on several locations and areas, give both insight in user experience, as pure application performance.
I'm very interested in anybody's additions, improvements and adjustments!
Answer by Yuriy L. ·
Your analysis is pretty comprehensive, I think you’ve covered most of the virtual/physical considerations. Here are my comments and additions.
Maintenance and Infrastructure
■ No hardware parts that can break down, and need to be replaced (except in host environment). Host environment is usually much more redundant, and break-down of one or even a few hardware components usually cause no or very minimal (in order of seconds) downtime, whereas in case of hardware usually the environment is down up until the breakdown part is replaced, and, in case of a hard drive, the contents is restored.
■ No hardware life-cycle replacement (except on host), nor depreciation. With that said, ability to upgrade Windows and sometimes other software involved may be limited. Plus limitations might exist in upgrading host environments, so in virtual world you may also need to create the environment from scratch.
■ In case of major IS changes a simultaneous downtime or performance degrade of multiple environments is possible.
■ Since images share resources of the host environment, measurements represent not only the application being monitored, but also the load of the host environment.
Answer by Antoon R. ·
That’s a very good article you wrote. I've only a few additions. We made the decision to move from physical agents to virtual agents about 3 years ago.
There is one pro for physical agents you didn’t mention. You can use agents with different memory / CPU sized according to the actual state of the pcs in your firm.
There is one extra con we noticed in our firm: The images for the virtual pcs are a slight different from the images of the physical pcs. That’s because that there is other hardware underneath the agents.
In our firm we have an extra con: Our virtual pcs are the only virtual pcs in the production environment. All the other virtual pcs are in our development and test environments. (We use citrix quite a lot in our firm, but that’s a XenApp Desktop environment and therefore not a real pc.)
Greetings from a dutch guy in Germany to Utrecht