Virtual Vs. Physical: Enterprise Synthetic Agents

The idea for this article was the need we have for a good overview of the Pro's and Con's of having Virtual agents over Physical agent devices. So far I did not find such an page elsewhere.

I can come up with several, and obvious, benefits and penalties, but I wanted to have it as true and complete as possible. This so it can be used with business case discussions. Hence this article is always open for improvements.

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 could think of with some help from the community:

Maintenance and Infrastructure

Virtual Pros:

• Lower hardware costs (same OS license requirements apply), no additional hardware per agent
• 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
• Faster deployment, more in minutes than in days
• Availability; when a physical device is broken, it takes hours to days, fix or replace. A virtual device can be replaced within a short time.
• System resources as CPU, memory and disk-space can be added easy, and almost instantly
• Worldwide deployment without export/import restrictions, customs, or local supplier or support dependencies
• VMs can be transported physically. No physical shipping/logistics involved for sending/returning units.
• The right/standard VM can be build centrally, and deployed with greater ease. Physical systems have to be imaged, and likely need extra installation work after imaging.
• Deployment from inside a data-center can be seen as a pro in certain situations, bringing monitoring close to the platforms to be measured, without bringing extra hardware into the DC. If policy's allow bringing in desktops at all.

Virtual Cons:

• Requires Virtual Hosting environment (e.g. VMware/ESX)
• Placement restricted to the availability/position of a hosting platform or server. Often this is a datacenter/dataroom, with it's own network access. Although in situations that can also be considered a pro.
• A physical device can virtually be placed anywhere, and there where the real users are (LAN). (For VM's this would mean placing a host in such location).
• A virtual agent (in a DC) is not as representative as a standardized workplace machine in terms as simulating end user experience. The hardware specs are not aligned. Images for virtual pcs are slightly different from the images of the physical pcs. That’s because that there is other hardware underneath the agents.
• Deploying VMs requires base-lining well the performance of the VMs together with physical workplaces, and record and anticipate on the differences.
• Overload on the VM platform could impact the VM's performance.
• The need of specific hardware, such as graphical interfaces, requires physical units.
• The 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.

Physical Pro:

• A clear physical agent pro, is the flexibility to place an agent in a hotspot when and where needed in case of need of need of ad-hoc measuring; Even installing software on an existing user desktop is an option.
• You can use agents with different memory / CPU sized according to the actual state of the PCs in your firm.

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.

Management

Virtual Pros:

• Ease of remote control/accessibility.
• No dependency on local staff, for physical control/management.
• Power control through the host. No PDU/power(-over-IP) switches, or local staff required.
• Remote (KVM) access through the host. No separate KVM (Keyboard/Video/Mouse) switches or over-IP solutions required.
• When OS not reachable, or network port not functioning, a VM still can be reached through the host.

Virtual Cons:

• Access required to hosting server/platform; To control the VM, the staff that manages the agents need to be able to have access to control the VM through the host; Modern virtual platforms should be able to manage the necessary access control; This involves an extra layer of security account management;
• If for a reason access is not possible to the VMs host, there is adependency on other teams managing the VM infrastructure.
• In case of major IS changes a simultaneous downtime or performance degrade of multiple environments is possible.

Security

Virtual Pros:

• The unit and it's console are automatically protected by the host platform; No one can walk in and just access the machine. Since the agent requires an unlocked screen to run it's tests, this imposes a security risk when the physical agent is placed in an open office space.
• No physical vulnerability, no secured area or protective measures necessary, where a physical unit in an office space would be vulnerable to hardware tampering, like unplugging, powering off, removal of peripherals.

Virtual Cons:

• As stated before, the control of the VM depends on the (level of) access to the hosting platform.
• A proper access control configuration is required, allowing the right personal control and access the VM.

Measuring

Virtual Pros:

• Perhaps the stability of the virtual platform and the (data center) network might be in favor of a virtual agent, in terms of a clean 'network' for measurements.
• The use of virtual agents is great for base-lining application performance measurements. However the biggest difference is in the:

Virtual Cons:

• The measurement of virtual agents, may (or will) not be 100% representative for End User Experience Measuring, in relation to the use of physical agents that use company standardized hardware, that regular users utilize. Although nowadays there is a lot of variety in user hardware as well.
• The use of virtual agents involves measuring and defining the baseline measurements in detail, and compare these with the results of the physical equivalents. This to determine if there are deviations between the two, that may need to be taken into account. These differences might be very small, but present.
• Measurements right there where the host spots are, is easier with a physical device that can be placed anywhere when needed.
• Since images share resources of the host environment, measurements represent not only the application being monitored, but also the load of the host environment.

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! I would like to give special thanks to @Antoon Rodoe and @Yuriy Look for their valuated review and input while coming to this Article.

Happy Measuring!

Frans