Recognizing Faulty Power Settings in a Performance Test - Login VSI Tips and Tricks
In performance testing your virtualized desktop environment, almost inevitably you will find discrepancies in your configuration. Some discrepancies will not have any impact on end user performance while others will have a big impact. During a performance test, it’s easy to overlook the telltale signs if you just don’t know how to recognize them. The one I see a lot during test analysis is caused by power settings that are not set correctly. In this blog post I will show you how to recognize faulty power settings when you are testing.
The screenshot below shows the Login VSI Analyzer with an overview of a test conducted with 220 users. If you look closely, at about 38 users the average response time drops and occasionally falls even below the baseline.
This drop in response time wouldn’t be too strange when working with real users, but as my users are simulated (using Login VSI), it is cause for further investigation. The simulated users are still executing the exact same actions, but for some reason the system responds much slower. We can safely assume that at the beginning of the test with just a few users logged on, the performance for these users should be at its best, indicating the lowest response time numbers. Then why does response time drop with more users? Simple. As more and more users log on to the machine, it shifts power states from a power-saving mode to a higher performance power mode, hence indicating lower response times.
So what’s the solution? Simple again. Configure your machines to stay in high performance mode, either by selecting it directly or by using a custom profile. This way your users will always benefit from the best performance available.
Configuring power management settings for Dell PowerEdge servers
If you want more information about analyzing Login VSI results, please read my previous blog. If you have any questions about Login VSI, you can also contact me on Twitter @MarkPlettenberg.
For more information on power and performance, see these other helpful blogs:
- Helge Klein - The Effects of HP’s Power Profile on vCPU Performance
- VMware VROOM! Blog - Power Management and Performance in VMware vSphere 5.1 and 5.5