Bob Wescott: Seven Insights into Queueing Theory: "The slower the service center, the lower the maximum utilization you should plan for at peak load. The slowest computer resource is going to contribute the most to overall transaction response time increases...
...It’s very hard to use the last 15% of anything. As the service center gets close to 100% utilization the response time will get so bad for the average transaction that nobody will be having any fun.... The closer you are to the edge, the higher the price for being wrong.... Remember this is an average, not a maximum. If a single service center is at 75% utilization, then the average response time will be 4x the service time. Now a specific job might arrive when the service center is idle (no wait time) or it might arrive when there are dozens of jobs ahead of it to be processed (huge wait time).... For resources with multiple service centers, you can run them hotter than single service center resources, but you have to be prepared to add capacity quickly or suffer horrendous jumps in response time. Most companies are much better at understanding real pain they are experiencing now, as opposed to future pain they may experience if they don’t spend lots of money now. Most corporations only learn through pain....
Show small improvements in their best light. If you see some change that will make the system 10% more efficient, when is the best time to tell your boss about it? If you reveal your idea during the slow season when the system is 20% busy, that small efficiency improvement will hardly be noticeable. If you wait until a busy time of the year when your system is on the ugly part of the response time curve you will be a hero and be a shoo-in for a promotion. Of course, I’m kidding here. When you do find a silly waste of resources that can be easily fixed, take the time in your presentation to show the effect this small fix will have at the next seasonal peak...
#noted
