System information

Chapter 1. Introduction to LPAR on IBM System i5 29
Figure 1-25 Logical partition memory configuration
The Hardware Page Table for this logical partition is calculated by dividing the total memory
available for the logical partition by 64. The result is then rounded to the next whole number.
For the configured memory of the logical partition in Figure 1-25, the HPT size is 10752 MB /
64 = 168 MB. The Power Hypervisor will then allocate 256 MB memory for this logical
partition HPT.
Another memory allocation in System i5 system is for Power Hypervisor memory. The Power
Hypervisor requires some amount of memory to perform logical partitioning functions in
System i5 system. There are several factors affecting the Power Hypervisor memory
requirements:
1. Logical partition memory configuration
2. Maximum amount of memory assigned to the logical partition
3. Virtual I/O used by logical partition
4. Total number of logical partition in the System i5 system
“Processor use in System i5 LPARs” on page 8 discusses the Processors, which are grouped
into nodes in System i5 system. Each node is interconnected to share its memory. Memory
access between nodes is slower than memory access from local node. It means that memory
access by processors from within the same node is faster than memory access by processors
from a different node.
The Power Hypervisor will attempt to group processors and memory together for better
logical partition performance, especially for dedicated partitions. The Power Hypervisor tries
to avoid too many remote memory access operations, which may slow down the job’s
execution, because it takes a longer time to access memory not in the same node with
processors. The Power4 firmware allocates memory equally from all nodes, which leads to
more remote memory access than System i5 Hypervisor does.