5.1. Dynamic logical partitioning overview
DLPAR, or dynamic logical partitioning, supports the following dynamic resource change in a partition without requiring a partition reboot:
Resource addition
Resource removal
By achieving the resource changes sequentially in the following order on two partitions in a system, the specified resource can be moved from a partition to another partition:
Resource removal from a partition
Resource addition to another partition
This resource movement is implemented as single task on the IBM Hardware Management Console for pSeries (hereafter referred to as HMC), although it is actually composed of two separate tasks on two partitions internally.
A resource is either of the following types:
CPU
The granularity of a CPU resource of a DLPAR operation is one CPU. More than one CPU can be specified as a resource of a DLPAR operation.
A partition must be assigned at least the minimum number of processors specified in the partition profile, and it can be assigned up to the maximum number of processors specified in the partition profile.
Therefore, you can dynamically add or remove processors for that partition within the range of the minimum and maximum values.
Memory
The granularity of a memory resource of a DLPAR operation is 256 MB[1]. Multiplies of 256 MB memory can be specified as a resource of a DLPAR operation.
[1] This memory chunk is referred to as a logical memory block (LMB).
A partition must be assigned at least the minimum size of memory specified in the partition profile, and it can be assigned up to the maximum size of memory specified in the partition profile.
Therefore, you can dynamically add or remove memory for that partition within the range of the minimum and maximum values.
The granularity of an I/O resource of a DLPAR operation is a PCI slot with a PCI adapter. Multiple I/O slots can be specified as a resource of a DLPAR operation. If a PCI adapter has multiple ports, all the ports and devices configured beneath the ports are treated as a resource.
For example, if a 10/100 4-Port Ethernet adapter (FC 4961) is selected, both Ethernet devices (entX0) and interfaces (enX) configured on this adapter are treated as a single resource.
A partition must be assigned all the adapters specified as required in the partition profile, and it can be assigned adapters specified as desired in the partition profile. Therefore, you can dynamically add or remove only adapters specified as desired for that partition.
You cannot remove I/O slots listed as required; however, you can remove I/O slots listed as desired, or those that were added as a result of a DLPAR operation. In other words, a partition can currently contain an I/O slot that is not listed as either desired or required in the active partition profile.
Note
A DLPAR operation can perform only one type of resource change. You cannot add and remove memory to and from the same partition in a single DLPAR operation. Also, you cannot move CPU and memory from a partition to another partition in a single DLPAR operation.
Resources removed from a partition are marked free (free resources) and owned by the global firmware of system; you can consider these resources as kept in the “free resource pool.” Free resources can be added to any partition in a system as long as the system has enough free resources.
It is imperative to understand that the DLPAR function is not solely provided by AIX 5L Version 5.2, but it is supported by the integration of following components:
Hardware
A partitioning-capable pSeries server model is required.
Firmware
Depending on the models you have selected, a firmware update might be required.
HMC
HMC software Release 3 Version 1 or later is required.
Operating system
AIX 5L Version 5.2 or later is required.
If one of these components does not satisfy the requirement to support DLPAR, the function is not available. For example, if a partition is installed with AIX 5L Version 5.1, that partition does not support DLPAR, although the other partitions installed with AIX 5L Version 5.2 support DLPAR.