Load Testing in the Dinosaur Age

nighttime, and my boss showed up with pizza. (Was it the great philosopher Dilbert who said, "Pizza is the opiate of the bosses"?) "How's it going?" he asked. I explained what I was doing, and he seemed very excited about the whole thing. "That's great! Just think of all the money we'll save on beer and pizza!"

"Now that you mention it, there's that little matter of the bonus you promised me," I laughed. "Here, make yourself useful. You start on that end and I'll start on this end. Just log in to each one, start up RandyTest in the main directory, and then go on to the next one."

Thrilled to be doing something "technical," he complied. This time the speed of the dots didn't degrade as much every time a new terminal was activated. But when we got to around 50, something weird happened-the "refrigerator's" disk light suddenly started flashing furiously and all the dots slowed to a crawl! Apparently, I had overwhelmed the hard disk by having so many high-speed "virtual typists" save so many records so quickly. For these many years it has been my job to torture computers, but in this case, I needed a realistic load test that focused on the terminals.

I went back and adjusted my routine to simulate a range of slower typists. The adjustment allowed me to get almost 70 terminals up and running before the disk began to thrash and the screens froze up. By then my boss had finished his pizza and gone home, after congratulating me on a job well done. Well done? Depends on how you look at it, I guess. I couldn't see any way I could possibly back up our marketing claims without assuming that the average data entry clerk can't type faster than a nine-year-old! I had to set the typing speed to about ten words a minute before 100 terminals could run at once, and even then the dots were barely moving. But hey, that's what exaggerated marketing claims are all about, right?

The art and science of load testing has evolved quite a bit since those days, but the basics are still the same. Can a system or network of a given capacity deliver adequate performance under real-world usage load conditions? There is only one way to find out for sure, and that means putting the software "on stage" to see how it really performs. Fortunately, we've at least taken most of the legwork out of the process these days, with the sophisticated load testing tools that are available. And we don't even have to haul 100 (or 10,000) terminals into the lab to do it. Only the best Broadway shows run night after night-no messy setup and teardown with each production. If you can do your load testing this way, you are way ahead of the curve.