Using Pizza to explain IBM Sub-Capacity


Using Pizza to explain IBM Sub Capacity

By Mark Feinman – Siwel Consulting

My wife is a very smart woman, but when it comes to explaining to her what I do in IT, I might as well be speaking another language. And so it went when I was trying to describe to her the difference between IBM Sub-capacity and Full capacity as it pertains to IBM software. IBM defines Sub-capacity as follows: “Sub-capacity licensing lets you license an eligible software product for less than the full capacity of your server or group of servers. It provides the licensing granularity needed to leverage various multi-core chip and virtualization technologies.” That’s a mouthful that I know my wife would not have understood. So I decided to use a different approach:


The round pizza pie is a symbol most people recognize: besides being delicious if made right, it can be used to explain sub-capacity pretty well, too.

The full capacity of a pizza is the entire pie. The unit of measure of the pie is a slice. A large pizza (here in New York anyway) is divided up into 8 slices.

Suppose I own the pizza store and decide to use full capacity pricing of $10.00 for the entire pie. This means that I will only sell my pizza by the pie – the full capacity of the pizza – regardless of the number of slices you want – the sub-capacity you plan to eat. If you order 2 slices, I am still charging you for and giving you the entire pie – for $10.00 – even though you’re only eating 2 slices from that pie. This is great for me (especially if eight people order one slice each), but not for you.

Now suppose I came to my senses as the pizza shop owner and charge you only for what you eat – sub-capacity – which is something less than the full capacity of the pie. My price for sub-capacity – by the slice – is $2.00. Here you pay only for what you want. If you eat 2 slices, you’ll pay only for 2 slices of the 8-slice pie. This is sub-capacity as associated with pizza. Hungry yet?

In IBM terms, the unit of measure of a pizza is not a slice; IBM might call it a “segment” of the pie measured in “Pizza Value Units” or PVUs. However, everything else is basically the same. Let’s now take another look at our example, but this time for IBM pizza. Let’s assume our pizza pie’s full capacity is 800 Pizza Value Units or 800 PVUs and each PVU was 10 cents. The pizza is still divided into 8 segments, each of which would be 100 PVUs (800 / 8 = 100). If full capacity pricing was in effect, the IBM pizza would cost you 800 PVUs x 10 cents/PVU or $80.00, even if you ate only two segments. However, if sub-capacity pricing was in effect, those same two pizza segments would cost you 100 PVUs / segment x 2 segments = 200 PVUs x 10 cents = $20.00. Clearly, sub-capacity pricing would save you a great deal of money.

For IBM software, IBM calls the unit of measure for sub-capacity pricing “Processor Value Units”. This unit of measure is based on several things related to the processor. Different processors within the same family might have different PVU measures. So how do we relate this back to pizza?

The Pizza Value Unit counts mentioned above (80 for a single segment, 800 for the entire pie) assumed a regular cheese pizza without any extra ingredients. Suppose now you wanted to purchase two segments with extra cheese. That extra cheese makes the per-segment cost 110 Pizza Value Units, or 880 PVUs for the entire pie. What about sausage and peppers as a topping? That will be a per-segment cost of 115 PVUs or 920 PVUs for the entire pie. What if you wanted name brand mozzarella vs. generic store brand mozzarella cheese? Well, now that per-segment cost might be 120 Pizza Value Units.

Processor Value Units (PVUs) are based on extra, or different, “ingredients”, too. A PVU is a unit of measure used to differentiate licensing of software on distributed processor technologies (defined by Processor Vendor, Brand, Type and Model Number). A different processor type (i.e. dual-core, quad-core) could mean the difference between a 100 PVU product and a 120 PVU product. A different model number could mean the difference between a 100 PVU product and a 140 PVU product. So could the processor vendor and brand (i.e. AMD Opteron vs. Intel Xeon). Think of these attributes as pizza toppings that could vary the cost of licensing depending on the information about the processor.

Sub-capacity can save you big bucks. Don’t just look at the number of PVUs you might save – calculate the dollar figures based on the PVU count. The savings can be astounding. Using our pizza example, a pie with sausage and peppers at full capacity would be 920 pizza value units for the full capacity of the pie, while only two segments of the pie would be 230 PVUs. Yes, 230 < 920 Pizza Value Units is definitely a big savings, but it’s in a measurement that isn’t as meaningful as the dollar. So at 10 cents per Pizza Value Unit, $23.00 for IBM pizza using the sub-capacity model vs. $92.00 at the full capacity model is a savings of $69.00, which anyone, even someone outside of IT, can relate to. 5,000 PVU licenses doesn’t tell you anything. However, if one PVU costs $400, that equals $2,000,000.

Monetary savings my wife understands very well. And with that savings, you can buy a lot of … pizza.

Hope you found this article useful.


MF-LinkedInMark Feinman is a Senior Solution Architect for Siwel Consulting, Inc. He has ten years’ experience working with ITAM tools and technologies. Mark leads a team of developers in the installation, configuration and deployment of various asset management tools, including the IBM License Metric Tool and Siwel’s own Software Asset Management portal. Before joining Siwel, Mark was a Certified IT Specialist for the IBM Corporation, focused on the deployment of web conferencing across the entire enterprise. When not involved with ITAM tools in one form or another, Mark enjoys volleyball, bicycling, trains, pinball and spending time with his family. And pizza.


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  1. Frank Iati says:

    Well done Mr. Feinman! You take a concept that many find complex and make it simple through the use of a simple analogy that we can all identify with … especially pizza aficionados like us!

  2. Deborah Robinson says:

    Seconding Frank above. Thank you! (I usually only read and quietly consider articles, but this one demands an actual–if brief–comment.)

  3. Deepika says:

    Loved the analogy “Pizza Value unit ” 😛 …Delicious learning!!

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