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Calculation for Maximum Core Allocation
Calculation for determining maximum core allocation
When you are creating a vCMP® guest and allocating cores to that guest, the BIG-IP Configuration utility assists you by displaying only valid amounts of cores in the Cores per Slot setting. For example, for a chassis with B2100 blades, the BIG-IP Configuration utility displays Cores per Slot values of 2, 4, and 8, because these are the only valid choices for that blade platform. Some users, however, might want more detailed information about these selections to enhance their own understanding of core allocation on the vCMP system.
The total number of cores that you can allocate to all vCMP® guests (combined) on a blade depends on the number of physical cores that a single physical processor contains on a particular blade platform. For example, on a blade platform with hyper-threading support, each physical core represents two logical cores. Consequently, a blade platform with two physical processors, each with six physical cores (that is, 12 cores), has a total of 24 logical cores that the host can allocate for that slot. This illustration shows an example of the relationship of physical processors to logical cores.
Relationship of physical processors to logical cores
In addition to the total number of logical cores available for allocation on that slot, there is a maximum number of logical cores that the host can allocate to an individual guest on that slot. This number is restricted to the number of physical cores per physical processor, which means that you cannot allocate additional logical cores to a guest VM from any other processor on the blade. Therefore, if you know the number of physical cores per physical processor on your blade platform, you can use this simple calculation to understand the maximum number of logical cores that you can allocate to a guest on a slot:
Number of physical cores per physical processor * Number of cores per physical core = Maximum number of logical cores per guest
For example, if a blade platform has six physical cores per physical processor, and the number of cores per physical core is 2, then the maximum number of logical cores per guest on that slot is 12 (6 * 2 = 12).