Processor resource assignment in partition profiles
When you create a partition profile for a logical partition, you set up the desired, minimum, and maximum amounts of processor resources that you want for the logical partition.
The desired value is the resource amount that the logical partition gets if you do not over commit the resource on the managed system. If the desired amount of resources is available when you activate the partition profile, then the logical partition starts with the desired amount of resources. However, if the desired amount of resources is not available when you activate the partition profile, then the resources on your managed system are over committed. If the amount of resources that are available on the managed system is equal to or greater than the minimum amount of resources in the partition profile, then the logical partition starts with the available amount of resources. If the minimum amount of resources is not met, then the logical partition does not start.
If the managed system allows the configuration of multiple shared processor pools, then you can limit the number of processors that are used by a specific group of logical partitions by configuring a shared processor pool for those logical partitions and reassigning those logical partitions to that shared processor pool. For example, if you use per-processor licensing for IBM® i, and you have a limited number of IBM i licenses for your managed system, you can create a shared processor pool for the IBM i logical partitions on the managed system and set the maximum number of processing units for that shared processor pool to be equal to the number of IBM i licenses on the managed system. If you configure a shared processor pool and assign logical partitions to that shared processor pool, the number of processing units used by those logical partitions plus the number of processing units that are reserved for the use of uncapped logical partitions within the shared processor pool cannot exceed the maximum number of processing units that you set for that shared processor pool.
- The default minimum number of virtual processors is the minimum number of processing units (rounded up to the next whole number). For example, if the minimum number of processing units is 0.8, the default minimum number of virtual processors is 1.
- The default desired number of virtual processors is the desired number of processing units (rounded up to the next whole number). For example, if the desired number of processing units is 2.8, the default desired number of virtual processors is 3.
- The default maximum number of virtual processors is the maximum number of processing units rounded up to the next whole number and multiplied by two. For example, if the maximum number of processing units is 3.2, the default maximum number of virtual processors is 8 (four times 2).
When you activate the logical partition using the partition profile on the HMC, the logical partition is assigned the desired number of virtual processors. You can then use dynamic partitioning to change the number of virtual processors to any number between the minimum and maximum values, so long as the number of virtual processors is greater than the number of processing units that are assigned to the logical partition. Before changing the default settings, performance modeling should be performed.
- Minimum processing units 1.25
- Desired processing units 3.80
- Maximum processing units 5.00
- Minimum virtual processors 2
- Desired virtual processors 4
- Maximum virtual processors 10
When you activate the logical partition using this partition profile on the HMC, the operating system sees four processors, because the logical partition is activated with the desired value of four virtual processors. Each of these virtual processors has 0.95 processing units supporting the work assigned to the processor. After the logical partition is activated, you can use dynamic partitioning to change the number of virtual processors on the logical partition to any between number 2 - 10, so long as the number of virtual processors is greater than the number of processing units that are assigned to the logical partition. If you increase the number of virtual processors, bear in mind that you will less processing power supporting the work assigned to each processor.
