vparresources2.5 (2012 03)

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vparresources2(5) vparresources2(5)

(For OA Based Partition Management Systems)

Memory Granularity

The nPartition memory is sliced into multiple memory granules by ﬁrmware for ease of memory assign-

ment to vPars. The size of these memory granules can be optionally speciﬁed by the user. Memory

granularity refers to the maximum amount of memory that will be in each of these memory granules.

Note that memory granules should not be confused with actual memory DIMMs.

The granularity for SLM and ILM can be different and speciﬁed separately by the user. However, follow-

ing applies to both types of memory:

• Memory granularity is speciﬁed at nPartition creation time. Any modiﬁcation thereafter requires a

reboot of the nPartition.

• The minimum values (ILM and SLM granularity) are 256 MB.

• The default value is OS dependent and may be adjusted based on the total memory available in the

nPartition.

• Memory is assigned to virtual partitions in multiples of granule sizes.

Hewlett Packard recommends that users do not change the default memory granularity value chosen by

the system, unless there is a speciﬁc need to do that.

In a situation, where user wants to manually specify the memory granularity value, following rules apply:

• Any chosen granularity must be an integral power of 2, not just a multiple of 256. For example, 512 is

a legal value, but 768 is not.

• Although a granularity must be an integral power of 2, memory can be assigned in any multiple of

that value. For example, if the SLM granularity is 256 MB, it is legal to assign 768 MB of SLM to a

vPar.

• Itanium-based platforms have a platform-dependent limit to the number of SLM granules per blade or

ILM granules that may be conﬁgured. You can determine speciﬁc limits for your installation by using

the

parstatus command.

• User speciﬁed memory granularity value can be overridden by ﬁrmware because of certain restrictions

imposed by the distribution of memory among individual blades. In this case, memory granularity

chosen by ﬁrmware is used to round up the memory sizes assigned to individual vPars in the nParti-

tion. The vPar database is also updated to reﬂect these memory size adjustments, unless user has

explicitly disabled parspec change policy attribute for the nPartition.

• User should also take into consideration the maximum number of ILM and SLM granules per nParti-

tion supported for the platform. The number of memory granules possible in the nPartition with the

user speciﬁed memory granularity value and the total memory in the blades assigned to the nPartition

should be less than the maximum number of ILM (or SLM) granules per nPartition supported for the

platform. The user speciﬁed memory granularity gets automatically adjusted if the value speciﬁed is

not in conformance with the above rule, unless user has explicitly disabled parspec change policy attri-

bute for the nPartition.

• When new memory (DIMM) is added to the blades in an nPartition, memory granularity value may get

adjusted by ﬁrmware to meet the new memory distribution among the blades. In this case, memory

granularity chosen by ﬁrmware is used to round up the memory sizes assigned to individual vPars in

the nPartition. The vPar database is also updated to reﬂect these memory size adjustments, unless

user has explicitly disabled parspec change policy attribute for the nPartition.

• Memory granularity is applicable even when the nPartition is in nPars mode, though there is no real

use of memory granularity in nPars mode for this release.

Assigning Memory to a vPar

• The

-a mem::size option is used to assign size MB of ILM to a vPar.

• The

-a socket:socket_id :mem::size option assigns size MB of SLM from socket socket_id to a

vPar.

If size is not an integral multiple of the granularity of the speciﬁed memory type, vPars normally adjusts

it upward to the next granule boundary.

In a vPar environment, either of the above command line options cause the system to reserve the indi-

cated memory, if it is available. However, actual memory ranges are only assigned to the vPar when it is

booted. These ranges may be different from boot to boot.

HP-UX 11i Version 3: March 2012 − 5 − Hewlett-Packard Company 5