Specifications

Chapter 3. Virtualization 79
Draft Document for Review September 2, 2008 5:05 pm 4405ch03 Virtualization.fm
򐂰 Select whether the partition will be able or not to access extra processing power to “fill up”
its virtual processors above its capacity entitlement. Selecting either to capp or uncapp
your partition. If there is spare processing power available in the shared processor pool or
other partitions are not using their entitlement, an uncapped partition can use additional
processing units if its entitlement is not enough to satisfy its application processing
demand.
򐂰 The weight (preference) in the case of an uncapped partition.
򐂰 The minimum, desired, and maximum number of virtual processors.
The POWER Hypervisor calculates partition’s processing power based on minimum, desired,
and maximum values, processing mode and also based on other active partitions’
requirements. The actual entitlement is never smaller than the processing units desired value
but can exceed that value in the case of an uncapped partition and up to the number of virtual
processors allocated.
A partition can be defined with a processor capacity as small as 0.10 processing units. This
represents 1/10th of a physical processor. Each physical processor can be shared by up to 10
shared processor partitions and the partition’s entitlement can be incremented fractionally by
as little as 1/100th of the processor. The shared processor partitions are dispatched and
time-sliced on the physical processors under control of the POWER Hypervisor. The shared
processor partitions are created and managed by the HMC or Integrated Virtualization
Management.
This system supports up to a 16-core configuration, therefore up to sixteen dedicated
partitions, or up to 160 micro-partitions, can be created. It is important to point out that the
maximums stated are supported by the hardware, but the practical limits depend on the
application workload demands.
Additional information on virtual processors:
򐂰 A virtual processor can be either running (dispatched) on a physical processor or standby
waiting for a physical processor to became available.
򐂰 Virtual processors do not introduce any additional abstraction level; they really are only a
dispatch entity. When running on a physical processor, virtual processors run at the same
speed as the physical processor.
򐂰 Each partition’s profile defines CPU entitlement that determines how much processing
power any given partition should receive. The total sum of CPU entitlement of all partitions
cannot exceed the number of available physical processors in a shared processor pool.
򐂰 The number of virtual processors can be changed dynamically through a dynamic LPAR
operation.
3.2.3 Processing mode
When you create a logical partition you can assign entire processors for dedicated use, or you
can assign partial processor units from a shared processor pool. This setting will define the
processing mode of the logical partition. Figure 3-1 on page 80 shows a diagram of the
concepts discussed in this section.