5.1. Dedicated Processors

An LPAR can either use only dedicated processors or only shared processors, but not both at the same time. If dedicated processors are used, these are only available to one LPAR (exceptions later) and cannot be used by other LPARs.

Partitioning with dedicated processors
Figure 5.1: Partitioning with dedicated processors

Figure 5.1 shows an LPAR with 2 dedicated processors (blue). When creating a new LPAR, the proc_mode attribute can be used to specify whether dedicated processors or shared processors are to be used:

proc_mode : processor mode
ded - dedicated processors
shared - shared processors

A new LPAR can be created with the “lpar create” command. To use dedicated processors, the attribute proc_mode must be specified with the value ded on the command line:

$ lpar -m ms02 create lpar1 proc_mode=ded
.
    > lpar1
$

The option “-m” with the target managed system must be specified, it defines on which of the managed systems the LPAR is to be created. The LPAR name, here lpar1, is optional. If no name is given, the LPAR tool generates a unique name.

A newly created LPAR is initially not activated. The greater part of the LPAR configuration is stored in a profile that is created when the LPAR is generated. By default, the name standard is used for the profile, but a different default can also be stored. A look at the profile standard shows that the LPAR was configured with a dedicated processor:

$ lpar -p standard lsproc lpar1
           PROC        PROCS           PROC_UNITS                       UNCAP   PROC
LPAR_NAME  MODE  MIN  DESIRED  MAX  MIN  DESIRED  MAX  SHARING_MODE     WEIGHT  POOL
lpar1      ded   1    1        1    -    -        -    keep_idle_procs  -       -
$

If an LPAR is to have more than one dedicated processor, the desired number of dedicated processors can be specified using the desired_procs attribute:

$ lpar create -m ms02 lpar2 proc_mode=ded desired_procs=2
    > lpar2
$

In the profile standard of the LPAR lpar2, 2 dedicated processors are configured as desired:

$ lpar -p standard lsproc lpar2
           PROC        PROCS           PROC_UNITS                       UNCAP   PROC
LPAR_NAME  MODE  MIN  DESIRED  MAX  MIN  DESIRED  MAX  SHARING_MODE     WEIGHT  POOL
lpar2      ded   1    2        2    -    -        -    keep_idle_procs  -       -
$

In addition to the desired_procs attribute for the desired number of dedicated processors, there are two other attributes, namely min_procs and max_procs. Just like desired_procs, these attributes can also be specified on the command line when creating an LPAR. The value of min_procs must be less than or equal to the value desired_procs, which in turn must be less than or equal to the value max_procs:

min_procs <= desired_procs <= max_procs

The value of min_procs comes into play at least in the following two situations:

    • An LPAR is activated, but not as many processors are available as required by desired_procs. In this case, PowerVM reduces the number of processors allocated to the LPAR to a smaller number. However, the value of min_procs must not be undercut.
    • With an active LPAR with the operating system running, processors can be dynamically added or removed without having to stop the operating system or applications. The number of processors can be increased to a maximum of the value of max_procs or reduced to a minimum of the value of min_procs.

As just described, the value of max_procs is taken into account when dynamically increasing the number of processors.

Which attributes can be specified and which possible values these attributes have, can be looked up in the online help:

$ lpar help create
USAGE:
lpar [-h <hmc>] [-m <ms>] [-p <profile>] create [{-b <blueprint>|-s <source_lpar>}] [-v] [<lpar>] [<attributes> ...]

DESCRIPTION

Create a new LPAR on a managed system.

-b : blueprint to use for creation'
-s : source LPAR to use as blueprint'

Valid attributes:
name : name for the LPAR
lpar_id : the ID of the LPAR
profile_name : name of the default profile
lpar_env : type of LPAR
aixlinux - AIX or Linux (default)
os400 - IBM i
vioserver - virtual I/O server
min_mem : minimum amount of memory in MB
desired_mem : desired amount of memory in MB
max_mem : maximum amount of memory in MB
mem_expansion : Active Memory Expansion
0 - disable AME
1.00-10.00 - expansion factor

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