IBM i running in the Cloud: CPU, vCPUs and software licensing

If you are planning to move your IBM i workloads to the cloud, this is something you need to understand and know to avoid surprises in your project costs.

Most of you know that IBM i can run on different clouds

Most of you know that IBM i software licensing base their cost in different values from your box and/or LPAR settings:

• Software Group: P05, P10, P20,...
• Amount of CPUs in your LPAR or the entire system: 1,2,3,... cores
• System Type and Model: 9009-41A, 9406-520, etcetera
• Processor Feature: EP10
• IBM i releases
• Amount of Users

Some of you know that you can control the amount of CPUs, vCPUs, and CPUs in a pool using the HMC, so you can size or estimate the license cost for your third party software.

But...

Not all of you know how CPUs, vCPUs and CPU Pools work.

Not all of you know how IBM Power hyperscalers (cloud vendors) assign this value to your LPARs/Instances/VMs and how this could modify your licensing costs.

How CPU, vCPU and CPU Pools work?

If you haven't read this article yet, I recommend this amazing post by Anthony Akens from IP4G:

IBM Power for Google Cloud - Entitlement and vCPU

There are also interesting documents from IBM like this:

https://www.ibm.com/docs/en/power8?topic=processors-virtual

Basically:

• A Processor pool is a CPU grouping you can assign to LPARs so you can limit the maximum amount of units.
• CPU can be used in dedicated, shared capped or shared uncapped mode.
• Dedicated: You assign whole processors (1,2,3,4, n) to your LPARs, and the compute power is not shared.
• Shared Capped: You can assign fractional amounts of CPU and you share unused compute power with LPARs at the same processor pool.
• Shared Uncapped: You can assign fractional amounts of CPU , you share unused compute power, and you can ask for compute power from other LPARs on the same processor pool.
• You can set the amount of CPU in 1/100 fractions, starting from 0.05 units
• A vCPU is a unit used to limit the maximum amount of compute power you can ask in Shared Uncapped mode.

When you have your own system with your own HMC or vHMC, you can control how things work:

You can assign the amount of CPUs, vCPUs, maximum, minimum and shared capacity without any restriction but the existing resources and system limits.

You can set processor pools to share CPUs from multiple LPARs and limit licensing.

What changes when you move to the cloud?

But when you "shift" your LPARs to the cloud, you can find new rules, some of them specific to the vendor/hyper-scaler you have chosen:

vCPUs:

• IBM Power Virtual Server and IP4G : Both set the amount of vCPUs rounding up the number of entitled CPUs. ie: 0.25 = 1 vCPU, 1.75 = 2 vCPUs
• Skytap: vCPUS can be set between 1 and the maximun, based on this formula (check on Skytap's porta). To make things easier, starting at 8GB of memory you can have up to 4 vCPUs for your IBM i LPAR.

Entitled CPU:

Is the minimum warrantied amount of CPU you can use.

• IBM Power Virtual Server and IP4G : You can set CPU cores in 0.25 increments, starting at 0.25 units. The maximum amount of cores per LPAR for SXX22 server models is 4 (P10 Software Group). If you need more compute power you will need to use a bigger box, and prices will go up.
• Skytap: Entitled CPU is based on the amount of memory you set in your LPAR. You can get 1 CPU every 50GB of memory you assign, up to 4 CPUs per LPAR.

CPU Pools

IBM Power Virtual Server and Skytap use the DEFAULT processor pool. This means you have "theoretical" access to 20 CPUs/Cores and this can confuse some software products.

Special Cases

IBM Power Virtual Server allows to use a complete server for your own purposes, allowing a more granular CPU setting. You can also work with Processor Pools for improved workload management.

How Software knows what should I pay?

Most software usually check the amount of CPUs in your pool using the API QLZARCAPI:

CALL QLZARCAPI        

This will show you the amount of total CPUs in this box, the CPUs in your Pool, the Pool, the entitled CPU and the vCPUs: minimum-desired-maximum for your instance/LPAR.

This is ok for your On-Premise environment or Skytap, because you can have a small amount of CPUs with a big amont of vCPUs.

Let say you have a 0.25 cores LPAR in Shared Uncapped Mode. When running in IBM PowerVS or IP4G, you can grow up to 1 CPU (1vCPU) dinamically. But the API will show you can grow up to 4 CPUs/Cores, so software vendors could charge you with 4 CPU licenses.

You can change the Shared Uncapped CPU mode to Dedicated or Shared Capped, but depends on the software you use if this change could help.

A more conservative and easy (but probably more expensive) way to fix this is using Dedicated CPUs.

What can I do?

You need to ask your 3rd party software vendors to switch to a Cloud Licensing model. Traditional licensing models will make you struggle with software products.

I suggest to read my previous article on how to put more than one LPAR on the same box. This could help you reduce costs with serial/number-based licensing models.

IBM Power Virtual Server tip: Multiple LPARs with the same Serial Number

Remember, the cloud is a growing space with new updates every month or even every week. Read the details on each portal, ask your Business Partner or Cloud consultant, and make some research before making the move.

You can also send me your questions. I will find a space to answer when I know the answer or have the contact in my list 8-D

Good Luck!

Diego E. KESSELMAN

IBM Champion

ESSELWARE Soluciones