PowerVM (Power Virtual Machine):

PowerVM formerly known as Advanced Power Virtualization, it is the virtualization solution for AIX.
PowerVM has 3 editions:

Express Edition: Hypervisor, DLPAR (3 servers), VIO (1 server), IVM, NPIV
Standard Edition: +DLPAR (254 servers), + VIO (2 servers), +HMC, +Multiple Shared Processor Pools, + Shared Storage Pools
Enterprise Edition: ++Active Memory Sharing, ++Live Partition Mobility

Intergrated Virtualization Manager (IVM)
For a smaller environment, not all functions of an HMC are required, and the deployment of additional HMC hardware may not be suitable, so IBM has developed the IVM, a hardware management solution that performs a subset of the HMC features for a single server, avoiding the need for a dedicated HMC server.
IVM manages standalone servers so a second server managed by IVM would have its own instance of the IVM. With the subset of HMC server functionality, IVM provides a solution that enables the administrator to quickly set up a system. The IVM is integrated within the Virtual I/O Server product.

POWER Hypervisor
POWER Hypervisor is the foundation of IBM PowerVM. It is a firmware layer sitting between the hosted operating systems and the server hardware, and it is always activated.
It delivers functions that enable capabilities: dedicated or micro partitioning, virtual processors, virtual ethernet- scsi- fibre channel- adapters and virtual consoles.


LPAR – Dedicated processors

Dedicated processors are whole processors that are assigned to dedicated-processor partitions (LPARs). The minimum processor allocation for an LPAR is one (1) whole processor, and can be as many as the total number of installed processors in the server.
Each processor is wholly dedicated to the LPAR. It is not possible to mix shared processors and dedicated processors in the same partition.

Micro-Partitioning
Micro-Partitioning is the ability to distribute the processing capacity of one or more physical processors among one or more logical partition.

Processing Capacity
(Processing Units, Entitled Capacity)

Processing capacity can be configued in fractions of 0.01 processors. The minimum amount of processing capacity that has to be assigned to a micro-partition is 0.1 processors.

On the HMC processing capacity is specified in terms of procesing units. (To assign a processing capacity representing 75% of a processor, 0.75 processing units are specified on the HMC.)

Once a micro partition is activated,  processing capacity is usually referred to as entitled capacity.

Capped and uncapped mode
Micro-partitions have  a specific procesing mode that determines the maximum processing capacity given to them from their Shared-Processor Pool:

Uncapped mode: processing capacity can exceed the entitled capacity when resources are available in their Shared-Processor Pool
(if there is competition amongst several partitions for unused processor capacity the uncapped weight will determine the sharing)
Capped mode: processing capacity can not exceed the entitled capacity

Uncapped Weight: Extra capacity is distributed between partitions in uncapped mode, by checking its uncapped weights. The higher the uncapped weight of a micro-partition, the more processing capacity the micro-partition will receive. (You must specify the uncapped weight when it is created.) The uncapped weight must be a whole number from 0 to 255. Default is 128. (If you set the uncapped weight at 0, the micro-partition will be treated as a capped partition.)

Virtual Processor
A virtual processor is a representation of a physical processor that is presented to the operating system. A virtual processor cannot have a greater processing capacity than a physical processor. The capacity of a virtual processor will be equal to or less than the processing capacity of a physical processor. In terms of capacity, a physical processor can supoort up to 10 virtual processors.

For example, if a logical partition has 1.80 processing units and two virtual processors, each virtual processor has 0.90 processing units.
By default, the number of processing units is rounded up to a whole number:
- if you specify 0.50 processing units, 1 virtual processor will be assigned.
- if you specify 2.25 processing units, 3 virtual processor will be assigned.

You can change the default configuration, and should be considered this, because in uncaped partitions the upper boundary of processing capacity in a micro-partition is determined by the number of virtual processors that it possesses.
For example, if you have a partition with 0.50 processing units and one virtual processor, the partition cannot exceed 1.00 processing units. However, if the same partition with 0.50 processing units was assigned two virtual processors and processing resources were available, the partition could use an additional 1.50 processing units.
The number of Virtual Processors can not be extended over 10X of the Entitled Capacaty.
(If EC=0,5 then the maximum number of Virtual Processor can not be over 5.)

Processor Affinity: Hypervisor always attempts to dispatch the virtual processor on to the same physical processor that it previously ran on. (To reduce contex switching…)
This behavior is called processor affinity.
If this is not possible, the POWER Hypervisor will broaden its search out to other processors.

Processor Folding: Virtual processor folding puts idle virtual processors into a hibernation state so that they do not consume any resources.             There are several important benefits of this feature: improved processor affinity, reduced POWER Hypervisor workload…

Desired, minimum and maximum values
When you set up a partition profile, you set up the desired, minimum, and maximum values you want for the profile. When a partition is started, the system chooses the partition’s entitled processor capacity from this specified capacity range.

When starting a micro-partition, preference is given to the desired value, but this value cannot always be used because there may not be enough unassigned capacity in the system. In that case, a different value is chosen, which must be greater than or equal to the minimum capacity attribute. If the minimum capacity requirement cannot be met, the micro-partition will not start.
The maximum value is only used as an upper limit for dynamic operations.

Shared-processor pools
In POWER5-based servers, a physical shared-processor pool is a set of physical processors that are not dedicated to any logical partition. Micro-Partitioning technology coupled with the POWER Hypervisor facilitates the sharing of processing units between micro-partitions.

Multiple Shared-Processor Pools (MSPPs)is a capability supported on POWE6. This capability allows a system administrator to create a set of micro-partitions with the purpose of controlling the processor capacity that the set of micro-partitions can consume from the physical shared-processor pool. The set of micro-partitions form a unit and this can be managed for example how much processor capacity it can use.

On all Power Systems supporting Multiple Shared-Processor Pools, a default Shared-Processor Pool is always automatically defined. The default Shared-Processor Pool has a pool identifier of zero (SPP-ID = 0) The default behavior of the system, with only SPP0 defined, is the current behavior of a POWER5 server with only a physical shared-processor pool defined. Micro-partitions are created within SPP0 by default, and processor resources are shared in the same way.

Storage Pool vs Volume Group
The IVM and HMC environments present 2 different interfaces for storage management under different names. Storage Pool interface under IVM is essentially the same as LVM under HMC. (These are used sometimes interchangeably.) So volume group can refer to both volume groups and storage pools, and logical volume can refer to both logical volumes and storage pool backing devices.

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