Virtualized LoadRunner?
Posted: April 21st, 2008 | Author: TnT Admin | Filed under: Concepts | Tags: LoadRunner, VMWare | No Comments »
Frequently, we do find questions relating to virtualizing the LoadRunner tool. Virtualization is becoming and had become a popular tool to leverage on the limited resources and allowed remote access the machines. Is LoadRunner suitable to work in a virtualized environment such as VMWare? What is the support level and compatibility with LoadRunner?
Let’s answer the mentioned questions first; YES, it’s supported according to official vendor in Document ID 43220 – Can LoadRunner be installed on VMware (virtual machine). However it is starting from LoadRunner 8.1 FP4 (also in version 9.0). Well straight forward, according to their QA team.
Well having said that, an official memo (the KB article), it’s best to hear from the ground, the users of the tool. James Pulley, who frequently contributes in the LoadRunner Yahoo Group shares his views and provided a list of recommendations on the topic. I believed that the recommendations (extracted from the discussion) will be very useful for individuals and organizations looking for answers on the proliferation of the virtualization tools.
Let’s look at the recommendations in details in order of the least influenced to the most influenced by virtualization.
[1] LoadRunner Analysis
The core issue associated with virtualization is the state of the virtualized system clock which is inconsistent in operation, so much so that time critical events do not illustrate reliable behavior Mercury Analysis. This is a very easily virtualized tool. There are no time critical components associated with the analysis engine, since all of the data has been collected by other hosts during the execution of the performance test.
This virtualized instance works best when the data store for the test results is in a Microsoft SQL Server database as opposed to the default data store of a Microsoft Access formatted data file. With the change in licensing with 8.1, this item can be promiscuous in its distribution and is no longer limited to just a single copy with a controller purchase.
[2] LoadRunner Virtual User Generator
As the workbench for the script development, there are very few time critical events associated with the development and the testing of scripts. Virtualized forms of Vugen work best on platforms which have hardwarevirtual machine extensions, such as the latest versions of the Intel CoreDuo processor and their AMD equivalents. Hyperthreaded machines seem to show in consistent performance as well – There is a knowledge base article on this hyperthreaded issue in the Mercury knowledge base.
Timing may be a little off in the log due to the clock issue noted above, but other than thisissue, the Vugen operates very well in a virtualized form. As with the Analysis engine, with the change in licensing with 8.1, this item can be promiscuous in its distribution and is no longer limited to just a single copy with a Controller purchase.
[3] LoadRunner Controller
As we move into the Controller timing becomes a more critical item. The controller itself can be virtualized without an issue, but because the timing record information collected is as an offset to the beginning of the test, an inconsistent clock on the controller can become an issue for monitor data with offset timestamps may not reflect the actual system clock.
[4] Load Generator/Injector
This is a layer which suffers from the most influence from the inconsistent clock issue for time critical events within a virtual machine and of all of the layers, this is the one which should be virtualized the least. The best test design would dictate that all of your generators have an identical hardware and software profile, a very difficult item to achieve invirtualized form which suffers from a virtualized CPU and a virtualized system clock.This time critical items is not something which would just impact LoadRunner. It also impacts other time critical processes, such as inability to run some functions for conferencing in virtualized PBXs.
A couple of articles that were referenced with regards to the virtualized system clock:
- Timekeeping in VMware Virtual Machines [from VMware]
- Clock in a Linux Guest Runs More Slowly or Quickly Than Real Time [from VMware]
- Clock in a Linux Guest Runs More Slowly or Quickly Than Real Time…[from MSMVP.com]
- FreeBSD 6.0 on VMware Server Time and Clock Slow Down [from My Digital Life]
Having bring forth the impact that may arise for vitrualization, you should be able to plan your load test deployment and arrive at a suitable decision that works in your environment.
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