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LG capacity issue

we have to perform 20,000 Vuser tests. there are two test one with web http, one with win socket and last one with RDP.

there is no other option we need to test 20K user.

 

how to find the capacity I needed ?

what is the best way to do it ?

 

Thanks

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Re: LG capacity issue

There is no easy answer to your question.  There is however a scientific\mathematical way to estimate how many virtual users your load generators can handle on a script by script basis and then you can verify those estimates with testing.

 

I recently wrote about this in the LoadRunner blogs.  You can read the entire article here:

 

http://h30499.www3.hp.com/t5/HP-LoadRunner-and-Performance/The-Protocol-Complexity-Matrix-and-what-it-means-for-your-load/ba-p/6559424

 

To summarize my blog post, you must first determine the footprint of each of your scripts.  The first virtual user and then the average of each additional virtual user.  Then you use the information about your script footprint to run it through a formula to estimate how many virtual users your LG's can handle based on the amount of memory (and in the case of RDP scripts GDI resources) available for the virtual users.

 

Memory however is only one aspect of how many virtual users can run on an LG and the other is CPU.  Exceeding more than 80% CPU regardless of how many virtual users are running is generally considered a bad thing for load testing.  

 

Once you have your estimate for how many virtual users might run on an LG you have to run a test with that many virtual users of that particular script.  The only way to determine this is to monitor the LG and when you are nearing the 80% CPU mark you take note of how many virtual users are running at that point and that is the upper limit.  Hopefully you will see that you will run out of memory before you run out of CPU and your estimate will become the actual.  If not you will have to reduce the estimate.

 

There are two other finite resources that you could run out of that are a bit harder to monitor.  Network bandwidth and Disk IO.  If you are maxing out either of these your results could be tainted.  You can monitor both directly on the Load Generator or by creating a monitor profile in PC that will add in the key measurement points.  How to determine if Disk IO or Network bandwidth are fully consumed is beyond the scope of this reply.

 

The key will be to test each of the scripts that you have developed and determine the footprint of each, then testing for CPU utilization and not overloading any load generator. 

 

Here are some additional things to take into consideration:

  • If possible only run one type\protocol script on a particular LG.  In other words, don't try to run WEB and RDP scripts from the same LG.  This will make it much harder to estimate memory and CPU usage in advance
  • RDP protocol has a large memory, CPU and GDI resource footprint.  Don't be surprised if 20 - 30 virtual users is all you can run per LG
  • If your LG's are virtual and not physical you will likely not be able to run the same number of virtual users or any protocol. The only way to know for sure it to test
  • Stop any programs that you can from running on the LG's  This might include corporate security, virus scanners, optimizers or other software that could be taking a chuck of memory and\or CPU.  You can re-enable these when the test is done.

I hope this helps answer your questions.

 

Regards

 

Craig Drummond

HP SW Premier Support, Technical Account Manager - ALM Products

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Re: LG capacity issue

Thanks for comprehensive answer.

if HP can develop online calculator at least basic level for each protocol that would be great.  that can serve as some sort of baseline.

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Re: LG capacity issue

The problem is not creating a calculator.  You can easily replicate my formula in MS Excel or any other basic calculating tool.  The problem is not knowing the exact footprint of the scripts that you develop. 

 

HP use to provide a footprint excel document but it proved to inaccurate because it could not account for the complexities of the actual script.  So you had to do this level of estimation and testing anyways and the footprint excel document is no longer available.

 

Craig Drummond

HP SW Premier Support, Technical Account Manager - ALM Products

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Re: LG capacity issue

thanks Craig for the link. It's indeed very useful.

 

I know it's very difficult to answer foot-print related queries, as many factors play key role(AUT/protocol/LG-memory etc..)

 

I recently did a 7000-vu load test using Citrix protocols and had a tough time in distributing the load. I had to open several terminal sessions to enure max capacity can be injected from each LG's.

 

btw, do you have any info on HP.LR.LG.Calculator.exe that comes with LR 12.0?

 

I think it's in technical preview mode....But any info on this would be of great help...Many thanks.

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