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# Thread: How to find out how many Virtual users

1. ## How to find out how many Virtual users

Hi,
I have to find out how many virtual users to use to stress a new web site and for how long.
Is there a process to determine how to do that?
And which infos do I need?
For example:
there are 64000 users in the peak hour and we assume that they will look at 5 pages before going.
If we assume 5 sec to load the page and 10 sec to read it how can I find out how many request per second (worst case? And once I have this info how can I stress the site?

Thanks
klulazz

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2. ## Re: How to find out how many Virtual users

http://www.stqemagazine.com/index.as...ntent=FEATURED

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Annemarie

One can greatly reduce the number of apologies delivered in life by simply thinking before speaking.
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Gone, but never forgotten...http://www.thewtcmemorial.com/

3. ## Re: How to find out how many Virtual users

Hello,
Actually you have all the information you need for computing your answer, right in your question believe it or not. Before answering your question it is important to understand that most stress tests will not involve user thinktimes- which you had mentioned was 10 seconds (the time it takes to read the page). Response times are something the load test cannot control but you can monitor the test results and determine when they are unacceptable (in your case 5 seconds)- which means the load is too great for the environment. Consider the following formula that can be used for stress or throughput testing:

Supported User Level = U
Virtual Users = V

U={V*[(test time in seconds/{thinktime+responsetime})/transactions per round]}

Now, let's plug in your information....

64000={V*[(3600/{0+5})/5]} or...
64000=V*144 which means...
V = 444.45

You will need 444 virtual users to complete your tests successfully. One thing to also consider, if you can tune your pages/application/servers to decrease your response time to 2 seconds, computing the formula again would show you would only need 177.7 users. Thats a big difference and a more attractive response time for internet orientated material.

One last thing, this is a formula I developed through trial and error and I believe it to work. If anyone can prove this formula incorrect, I'd love to know it- but I doubt it'll happen.

Hope this helps,
TestGuyTony

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4. ## Re: How to find out how many Virtual users

_

[This message has been edited by rwgreen1173 (edited 10-12-2001).]

5. ## Re: How to find out how many Virtual users

I think you should be getting this information from the Nonfunctional Requirements.
Also, a stress test, a load test, and a stability test are allvery different things.

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6. ## Re: How to find out how many Virtual users

Best practice is to test at a level significantly higher (2 to 4 times) than your planned peak. So for the criteria you've mentioned I'd use at least a 1,000 virtual user license to be safe.

Phil

7. ## Re: How to find out how many Virtual users

<BLOCKQUOTE><font size="1" face="Verdana, Arial, Helvetica">quote:</font><HR>Originally posted by klulazz:
Hi,
I have to find out how many virtual users to use to stress a new web site and for how long.
<HR></BLOCKQUOTE>
It depends on the type of the web site you are testing.
For a site that doesn't support "Sessions" you have to generate a transactional throughput only (infamous hits/min).
For a site supporting "Sessions" you have to emulate a transactional throughput as well as the number of concurrently connected users (virtual users).

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Yury
(yurym {at} hotmail [dot] com)

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