Configuring and Migrating Memory on vPars

• On HP Integrity servers, if the system contains a significant number of granules, it might

increase the boot time of partitions that are running the prior HP-UX 11i v2 release. Hence, if

the partition is running HP-UX 11i v2 and boot speed is a strong requirement, choose a large

granule size. The significant number of granules does not impact the boot time of partitions

running HP-UX 11i v3 and might not impact the boot time of partitions that run future HP-UX 11i

v2 releases.

• A very large granule size limits the number of partitions that can be created or might impact the

amount of memory a partition gets. For example, if the system contains 4 GB of ILM, choosing

1024 MB as the ILM granule size limits the number of partitions to 4 or less since the system

will contain four granules each with memory equal to or less than 1024 MB. Moreover,

memory contained in one or more granules can be less than 1024 MB because of memory

consumed by vPars monitor and firmware. Hence, do not set the granule size such that all

partitions are limited to a couple of granules at best. If not much memory movement will occur

between partitions once they are created, set the granule size such that each partition gets at

least a few granules.

• If periodic movements of memory between partitions (live or down) is a strong requirement, set

the granule size to the minimum amount of memory that will be moved between partitions. For

example, if your configuration is a small memory system and 128 MB is the minimum amount

of ILM that will be moved between partitions, then set the ILM granule size to 128 MB. On the

other hand, if it is a large memory system and 2 GB is the minimum amount of ILM that will be

moved between partitions, then set the ILM granule size to 2 GB.

• Changing granule size requires system and monitor reboot. If you plan to use different granule

sizes during different periods of time, create a vPars database for each granule size and boot

the vPars monitor with that database when the switch is required. On HP Integrity servers,

booting the monitor with a different granule size requires an update of granule size in NVRAM.

Unless that is done, the vPars monitor will reboot the system when it finds that the granule size

in NVRAM differs from the granule size in the vPars database. The vparenv command can be

used to change the granule size in the NVRAM, as shown below, before rebooting the system

to use the new database containing the new granule size:

# vparenv -g ilm:<size> –g clm:<size>

• The HP-UX 11i v3 kernel limits the large page size to the size of granule. Hence, when the

granule size is small it can sometimes lead to loss in performance especially if the partition

contains applications that benefit from large page sizes.

• On PA-RISC platforms, each partition’s HP-UX kernel requires memory below 2 GB to boot and

run. Memory below 2 GB is ILM. A portion of the first memory granule will be taken by the

vPars monitor for its code and data and hence cannot be used for the partition’s HP-UX kernel.

Excluding the first ILM granule, there should be at least one ILM granule below 2 GB for each

partition’s kernel. For example, if the granule size is 256 MB, there are 8 granules below 2

GB. Excluding the first granule, there are seven granules. On such a system, the system

administrator can create a maximum of seven partitions assuming the size of each partition’s

kernel is less than 256 MB. Hence, while choosing ILM granule size on PA-RISC platforms, the

system administrator should also consider the maximum number of vPars partitions planned for

the system

The size of the granule does not impact boot time of HP-UX 11i v2 kernel on PA-RISC platforms.