Loadtesting best practices – Part 1

Written by Ingmar Verheij on May 23rd, 2011. Posted in Performance testing

Before I start discussing best practices about loadtesting, let me first tell you what my definition of a loadtest is.

“Testing a system with representative load, to determine if the nominal load can be handled”.

This means that if you start loadtesting you need to know the nominal load and have an expectation of the outcome. You will find that most of the best practices has to do with preparation, not with fancy techniques. An different type of test that is frequently called a loadtest, is a stresstest. A stresstest has a different purpose, as can be read in my definition of a stresstest.

“Testing a system above its nominal load, with the purpose of determining if the system in the future can handle a bigger load and to find a bottleneck.”

LoadTest are commonly used to scale an environment. These environments can be a SBC environment like Citrix XenApp or Microsoft RDS, or a VDI environment. But other environments like file, print or webservers can be loadtested aswell. In fact, if you can create the load by simulating user actions, you probably can perform some sort of loadtest.

Now let’s start with the best practices. I’ve written these down in the past years while I was performing loadtests with the DeNamiK LoadGen, the best practices apply to (almost) all loadtesting applications. You can say I learned it the hard way. Although there’s nothing wrong with that, you can learn from my mistakes.

This is the first  part, focussing on the “basics”. Part two will focus on more advanced topics.


Bypass the 15ms inaccuracy

Written by Ingmar Verheij on April 21st, 2011. Posted in Performance testing

As Tim Mangan recently blogged, the system timer in a multiprocessor Windows machine operates at 15ms. The effect of this 15ms is that a measurement / calculation in your program can vary with 15ms. This is fine for most operations in your program, but not when you want accuracy to the millisecond.

Although the best solution to the problem is changing the system timers, as Tim Mangan wrote, a workaround is available.

Stresstest your printer drivers

Written by Ingmar Verheij on November 6th, 2009. Posted in Performance testing, Printing

A few days ago I wrote an article about the issues with printer drivers in a multiuser environment. In this article I advised you to test you’re printer drivers in a acceptance environment, preferably with real users testing. This can be achieved with a LoadTest / StressTest tool like the Denamik LoadGen, which is free up to 25 users. And since testing with 10 users is enough to stress a driver, there’s no need to buy a license.

Today I would like to tell you how this is done, step-by-step.

The goal
We’re going to try to use the printer environment as realistic as possible, but where focusing on the worst case scenario. Because where trying to find out whether the printer driver is functioning correct when multiple users are printing, where going to simulate that a number of users are printing to printers using the same printer driver.