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LoginVSI Analyzer - StartIndex cannot be less than zero

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24 Apr 2013 13:36 #911

Another forum post is similar to this but I thought I would create a new one since it was still open awaiting a response from that OP:

Attached is the zip of the results of a test (which run without issue, as far as I can tell):
The Analyzer tool does launch (you can continue past the error) and it will then display VSIMax/VSIMax Detailed/VSIMax Scatter tabs.

(In the attached example I've ran the test against a single device rather than multiple so keep the result data down.)

Any help/advice welcome.

Thanks, Paul.

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24 Apr 2013 15:49 #912

The image included is telling you:
• The VSI Baseline is 7201. The VSI baseline is the performance of the system when it wasn’t under load. We use this to calculate where the breaking point is for an environment.
• This environment example image was not at its breaking point yet, marked by the message: VSIMax not reached (meaning; one should/could add more users)

The analyzer will indicate VSI max when the VSI index average goes over the calculated threshold. In this case that threshold would be:
Baseline * 1.25 + 3000 = 1468 * 1.25 + 3000 = 4835
When the VSI index average (consistently) rises above 4835 you have reached the point at which we recommend not adding more users (VSImax). In this test you see not to be even near that point.

The default multiplier are listed here www.loginvsi.com/documentation/v3/analyz...s/calculating-vsimax

Look at the data this way. VSImax says something about the scalability of your system. It relies on the baseline to determine the threshold where the performance is no longer acceptable. To be able to do this VSI has to assume the baseline is acceptable performance. VSImax tells you how well that baseline performance scales. If you look at the baselines however you can see something about the base performance of the system.

The VSIMax calculation is very simple to understand. The first thing we do is measure applications those are a total of 7 actions:
• Copy new doc from the document pool in the home drive
• Starting Microsoft Word with a document
• Starting the “File Open” dialogue
• Starting “Notepad”
• Starting the “Print” dialogue
• Starting the “Search and Replace” dialogue
• Compress the document into a zip file with 7-zip command line

These actions are all calculated in the VSImax Data tab (which is taken from the Raw Data tab). The individual measurements of these actions are located in VSImax Detailed tab. The scatter charts shows all the measurements (dots) for the entire test.

In typical labs these 7 actions take somewhere between 1000 and 3000ms. Then what we do is for the first 15 of these measurements (so when there is no stress) we calculate an average. Let’s assume 1000ms for this example. This is what we call the baseline, please note that the baseline can change due to storage performance, anti-virus solutions, performance tuning etc. so it differs per environment.

To the baseline we add 25% of itself so 1000+250 = 1250
To that number we add a fixed 3000 ms so 1250 + 3000 = 4250

4250 would in this case be the response time at which VSIMax is reached, that is where we drop the X if it has been exceeded for three times in a row. In the graph then we simply check at how many active sessions this is.

For more info check: www.loginvsi.com/documentation/v3/analyz...s/calculating-vsimax

The Corrected and Uncorrected value for VSImax, VSI uses this mechanism to make sure that users that are stuck are not taken into account in the final performance score. If you start looking at these stuck desktops you will probably see: Crashed applications, Unexpected popups, Tests that did not start correctly etc. This is something you do have to troubleshoot the difference should typically be below 1 or 2 sessions.

Let me know if this is what you are looking for.



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24 Apr 2013 16:03 #913

May thanks for the response and explanation of what the VSI measurement pertains too, however this doesn't address the actual error message(Unhandled exception) noitification when opening up the results.

Out of interest are you able to open up the measurement log without this error occuring? Just to clarify I'm wanting to understand why that error is occuring, which actually prevets all tabs fro shwing within the analyzer tool (VSIMax/VSIMax Detailed/VSIMax Scatter/LoginScript/UserLoop/XDconnector/ZipTimer/VSIMax Data/Raw Data)

Regards, Paul.

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24 Apr 2013 20:12 #914

Hi Dark,

Sorry I misunderstood you (forgot to read the topic). Some nice info though.
Yes I am able to open the logs without the error occurring.

Are you using the latest version of the Analyzer?



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  • 's Avatar Topic Author
25 Apr 2013 07:40 #915

Hi Omar,

Version 3.5 Professional.
When runninf across VMs hosted in our Citrix environment no such error occurs and all tabs are displayed (VSIMax/VSIMax Detailed/VSIMax Scatter/LoginScript/UserLoop/XDconnector/ZipTimer/VSIMax Data/Raw Data).

Only seems to occur when using LaunchRDP and Blaze.
Although up versioning by be the best approach, this is not something I woudl want to do as we have baselined other environments using the 3.5 suite. So understanding why the issue is occuring is my preference.

Regards, Paul.

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28 Apr 2013 15:45 #919


The analyzer is stumbling over the empty LoginScript folder in your results folder. Removing the folder will solve the issue.

Updating the analyzer will solve the issue as well :)

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29 Apr 2013 07:31 #920

Thank you for the explanation. Only question left is why is that folder empty? Have I missed something on the target agent install perhaps?


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