System information

8 Logical Partitions on System i5
1.3 Processor use in System i5 LPARs
In this section we discuss the basic concepts of dedicated processor, shared capped
processor, and uncapped processor; how they work, how to configure in logical partition
configuration, and several aspects regarding the use of shared capped and uncapped
processors. Additionally, we also describe memory allocation for i5 OS logical partitions.
These are some of the topics we cover:
򐂰 System i5 processor overview
򐂰 Logical partition resources
򐂰 Dedicated processor
򐂰 Shared processor
򐂰 Shared uncapped processor
򐂰 Shared capped processor
򐂰 Virtual processor
򐂰 Configuring dedicated processors for the logical partition
򐂰 Considerations on using shared processors
򐂰 Memory allocation for the i5 OS logical partition
1.3.1 System i5 processor overview
Basically, processors and memory are grouped into nodes. The System i5 system unit may
contain more than one node. For example, System i5 system model 570 has two nodes which
contain two processors per node as shown in Figure 1-4. Memory cards are plugged into
each node in quad. These nodes are interconnected and can use each other memory. We
recommend that you spread all memory cards evenly across all nodes for better system
performance.
Figure 1-4 Interconnected processors and memory nodes in System i5 system
The iSeries processors cycle every 10 milliseconds. So the processors usage by all logical
partitions are limited within this 10 millisecond cycle. After 10 milliseconds, the processor
cycle will repeat automatically. For example, a logical shared partition with 0.6 processing
units will have up to 6 milliseconds of processing time in every processor cycle
(10 milliseconds).
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