Admin Alert: Getting Started with Trial Capacity on Demand, Part 1
December 5, 2007 Joe Hertvik
I recently activated a trial Capacity Upgrade on Demand (CoD) processor to increase my processing power on a System i 550 box. If you’re considering activating additional processors on your system, this week and next I’ll trace the steps I took to decide on activating another processor and how I got the process moving. Although there are a few pitfalls to avoid, adding extra processors to your machine isn’t that difficult.
What is CoD?
Capacity on Demand (CoD) is IBM‘s way of ensuring that you can quickly add extra capacity to later model System i servers, including models 550, 570, and 595. Unless you have currently activated the maximum number of processors that can be running on one of these machines, all of these models are shipped with additional processor capability already built into the server. These additional CPUs can be activated on a trial, temporary, or permanent basis. On some models, IBM offers memory CoD upgrades that can also be quickly activated.
In these articles, I’m focusing on activating additional processors to a System i model 550 machine on a trial basis. When you want to add processor capability on a more regular basis, IBM also offers different variations on the CoD model to provide permanent processor upgrades, on and off upgrades, reserve processors that kick in as needed, and utility style pay as you go processor upgrades, all of which are described below.
Why I CoDed
My situation involved a System i 550 box that was having problems completing its batch processing at night. This also caused a problem from a performance planning viewpoint since the holidays were the busiest period of the year for this client, and they were expecting their order volume to double, or even triple, during that time. While increased volume was a blessing, the fear was that an i550 that was already straining to handle the existing workload would be totally overwhelmed when order processing volume dramatically shot up. We looked at the situation and thought that adding another processor to the workload would help the machine better cope with the increased volume.
Before we could think about adding another processor, however, we had to determine whether the processor was really the cause of our performance problems. That meant undergoing a thorough performance analysis to determine where our bottlenecks were. After all, adding extra processors to the machine won’t help performance if the performance issues are actually caused by a lack of disk drive arms, too little working memory, operating system corruption, or PTFs that need to be applied. If we really believed that CPU utilization was our problem, we needed proof before adding another processor, even on a trial basis. Otherwise we were just spinning our wheels and spending excessive money before we figured out exactly what the problem is.
For System i performance analysis, there are three options you can take.
In these situations, I’ve found it’s important to either hire or get free experienced help for a couple of reasons. First, a good professional has been through this situation many times before with many different companies and they probably understand the trends inside your performance data better than you do. They also have the ability to take that data and easily model what your performance will be if you increase volume by a certain percentage or if you add additional resources. They have the knowledge to figure out what’s happening with your system and the tools to clearly present it to management. Most system administrators, like myself, don’t analyze system performance often enough to drill down as deeply into the data as we’d like.
The practical reason for hiring an outside firm to analyze system performance is that an outside expert brings credibility to performance analysis. The sad truth is that even if you’re the best performance analyst in the world, management will still be more willing to listen to an outside analyst simply because they have a reputation and the company paid good hard cash to have him come in. So if you’re thinking that you may have to hit management up for a permanent processor activation that will run into the tens of thousands of dollars, you may want to bring in an outside consultant to analyze the data, deliver the message, and present alternatives.
In my case we used an outside organization to produce a performance report, including what bottlenecks our system was currently experiencing, as well as an analysis on what would happen to our system if we experienced 20 and 30 percent growth. The report confirmed our suspicions. We needed additional CPU or the client’s processing speed (including green-screen access and Web site ordering) was going to bottleneck badly during the holiday season.
How Long Do You Need Additional CPU?
For the i550 system that I was working on, we had two processors activated out of a total of four processors that were shipped on the machine. This left us with one or two processors that we could turn on for the holiday season. The important question to answer was what was the least disruptive, most cost effective way to activate an additional processor for the client’s busy holiday season?
As I mentioned before, IBM offers several different flavors of CoD, depending on what type of machine you are running. The following CoD options for activating extra CPUs are available on later model machines. Note: Not all of these options will be available on every System i machine. Check with IBM to determine what CoD options are available for your box.
For a good overview of IBM’s CoD offerings, check out Big Blue’s System i Capacity on Demand Website.
For my situation, we chose Trial CoD because it allowed us to see how adding extra processors to our 550 would affect performance during the busy season. The 30-day trial period tracks fairly well to the holiday season between Thanksgiving and Christmas, and at the end of the 30 days we can make a number of decisions on what to do next with our processors.
If the trial goes well, we can elect to permanently turn on the processor (fairly expensive), sign a contract to turn on and turn off the processor as needed (On/Off activation), or purchase Reserve CoD so that our additional processor is activated when all the other processors on the system are busy. Using Trial CoD gives us some freedom to experiment with using additional processor power before making a decision (and possibly getting a capital request together) when the trial period runs out.
The Next Step
Once we understood what our options are for assigning and testing additional CPUs on our system, the next step was to figure out how to activate and start using the temporary CoD capability. I’ll cover those topics in next week’s column.