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IBM BladeCenter PS703 and PS704 Technical Overview and Introduction
The POWER Hypervisor abstracts the physical processors and presents a set of virtual
processors to the operating system within the micro-partitions on the system. The operating
system sees only the virtual processors and dispatches runable tasks to them in the normal
course of running a workload.
From an operating system perspective, a virtual processor cannot be distinguished from a
physical processor unless the operating system has been enhanced to be made aware of the
difference. Physical processors are abstracted into virtual processors that are available to
partitions. The meaning of the term
physical processor
in this section is a
processor core
.
When defining a shared processor partition, several options must be defined:
Processing units
The minimum, desired, and maximum processing units. Processing units are defined as
processing power, or the fraction of time that the partition is dispatched on physical
processors. Processing units define the capacity entitlement of the partition.
Cap or Uncap partition
Select whether or not the partition can access extra processing power to “fill up” its virtual
processors beyond its capacity entitlement, selecting either to cap or uncap your partition.
If spare processing power is available in the 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.
Weight
The weight (preference) in the case of an uncapped partition.
Virtual processors
The minimum, desired, and maximum number of virtual processors. A virtual processor is
a depiction or a representation of a physical processor that is presented to the operating
system running in a micro-partition.
The POWER Hypervisor calculates a partition’s processing power based on minimum,
desired, and maximum values, processing mode and 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 can be 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 0.1 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 0.01 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.
Partitioning maximums on the POWER7-based blades are as follows:
The PS703 can have 16 dedicated partitions or up to 160 micro-partitions
The PS704 can have 32 dedicated partitions or up to 320 micro-partitions
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.
The following list details additional information about virtual processors:
A virtual processor can be running (dispatched) either on a physical processor or as
standby waiting for a physical processor to became available.
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