YOGGIE YOGGIE MANAGEMENT SERVER Technical Information download pdf (Page 30)

12 Logical Partitions on System i5

for the partition to the tasks submitted for processing. The Power Hypervisor attempts to put a

partition back onto the last processor it used. However, if that processor is currently busy or

not available, it will go to any available one.

Resources of one partition are isolated from other partition resources of other logical

partitions, but there are ways for these active logical partitions to share their processing

power, memory, and I/O resources to another active logical partition. Dynamic LPAR/DLPAR

allows us to add, move, or remove processors, memory, and I/O resources to, from, or

between active partitions manually without having to restart or shut down the logical partition.

The LPAR only allocates physical processors to every logical partition. Micro-partitioning

allows logical partitions to share the processors in the shared processors pool. The shared

processors pool includes all processors on the server that are not dedicated to specific logical

partitions. Each logical partition that uses the shared processors is assigned a specific

amount of processing units from the shared processors pool. A logical partition that uses the

shared processors pool can always use the processing units assigned to them. However, if

the logical partition demands more processing power than its assigned amount, the logical

partition is set by default to use the unused processing units in the shared processors pool.

The number of processing units that the logical partition can use is limited only by the virtual

processor setting of the logical partition and the amount of unused processing units available

in the shared processors pool.

The Power Hypervisor will remember the last active configuration on the server for the next

managed system power up to standby or operating mode. The Power Hypervisor will assign

the resources for dedicated partitions to provide the optimum configuration for the dedicated

logical partition.

In order to create optimum resource allocation for logical partitions, the Power Hypervisor will

assign processors to the fewest number of nodes possible in the system. The reason is that

processors in a node share the same L2 and L3 cache. Using the processors in the same

node will improve logical partition performance since each processor will have better chance

to find data in the cache.

The memory portion dedicated for the Hardware Page Table (HPT) will be taken from

memory in a node that contains processors. The Power Hypervisor will assign as much

memory as possible in the same node as the processors. This is done to avoid too many

inter-node

remote memory access operations, which may slow down the logical partition

operation. The rest of the processor resources will be assigned to the shared processors

pool.

1.3.3 Dedicated processor

Dedicated processors are whole processors that are assigned to a single partition. If you

choose to assigned dedicated processors to a logical partition, the minimum number of

dedicated processors you must assign is one processor. If you choose to use dedicated

processors, once the logical partition is activated, only that partition can use the processors.

You cannot assign a partial processor to a logical partition that will use a dedicated

processor.

When the logical partition with dedicated processors is activated, the desired processor

resource will be assigned to that partition. If the logical partition demands more processor

resources, it will get only from the minimum up to the desired processor resources value. If

there is a processor failure, the system will attempt to accommodate the minimum processor

sizes for all partitions. If the minimum processor resource is not available for the logical

partition, the logical partition cannot be activated.

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