Will Extended Log effect the response time in any way?

Question

In Hp Load runner or any other performance testing tool if we enable the extended log, to log all the data returned by server. Will the performance reports generated, the response times etc.. will be effected in any way. I will just be logging the data which is returned by server anyways.

Answer 1

Answering my own question.

While running a load test if extended log is enabled it will be using up memory and processing capability of the Load Generator. It is always suggested to disable extended logging while running the test unless you have a specific reason to proceed otherwise.

Technically, no, the response time won't be impacted. Practically there will be a slight overhead on the time taken to send the request and when the response of the request is abnormally high that it takes more time to write the response stream to the log file. This will get added to the response time. However, for this to happen the load generator is already in a chaotic state and will invalidate the results anyway.

It can impact the hits per second (due to lag that might be created due to over utilization of load generator), the Load generators might crash but the response time will not be impacted.

Another disadvantage is the collation of results has higher chances of getting corrupted because there is just lot of data to be transferred and analyzed.

Answer 2

Yes. You will turn your local filesystem on your load generator into a drag anchor for your whole test. This is why it is recommended that you minimize the log level during your test.

Answer 3

In LoadRunner this time is reported as "wasted time". Best practice is to disable extended log during load test. See - http://h30499.www3.hp.com/t5/HP-LoadRunner-and-Performance/New-HP-Best-Practices-Document-quot-Load-Testing-Scenarios-Best/ba-p/6081497