HP-UX Virtual Partitions Administrator's Guide (includes A.04.06 and A.05.04)

to load and launch the maximum supported 8 vPars. If ILM
granularity is 256 MB, there are only 8 granules in the first 2 GB.
The Monitor uses portions of the first one. So it will only be
possible to load and launch 7 or fewer vPars. On ab Integrity
server, there is no similar constraint on the maximum ILM
granularity.
For CLM on PA-RISC platforms, and for both ILM and CLM on
Integrity systems, Hewlett-Packard recommends choosing the
largest possible granularity for performance reasons. The
granularity can be such that it is equal to the partition with the
least amount of that memory type. For example, if the system
contains 64 GB of ILM and the smallest ILM specification of any
vPar is 1 GB, then ILM granularity can be 1 GB. If the system
contains 64 GB of CLM per cell and the smallest CLM specification
from any cell of any vPar is 4 GB, the CLM granularity can be 4 GB.
+ For an Integrity server, the chosen granularity values must
also be written to system firmware storage. When the Monitor is
started and a vPar database is loaded, the values in the database
must match those in firmware, or the Monitor will not allow the
database to be used.
While in nPars mode, you should use the vparstatus and vparenv
commands to verify that the database and firmware granularities are
identical. If not, you must either create a new database with the
correct granularities using the vparcreate -g command, or change
the firmware granularities with the vparenv -g command.
Although memory is normally allocated in integral granules, some
memory ranges are withheld for use by the Monitor or by firmware. The
vparstatus -m command displays these ranges. Other ranges of address
space are simply non-existent. Because of this fragmentation, the
Monitor may assign your vPar slightly more or less than an integral
granule of memory when the vPar boots.
Memory: Choosing a Granularity Value and Boot Time (Integrity)
During the boot process of HP-UX on Integrity vPars, the time it takes to obtain the memory
layout information for the nPartition is relative to the number of memory granules configured
for the nPartition. The number of granules is dependent upon the granularity value:
number_of_granules = total_physical_memory_in_nPartition / granularity_value
If the granularity value is too small, the number of granules will be too high and processing all
the granules during boot up may take a long time.
On Integrity systems, it is important to chose an appropriate granularity value that does not
cause slow boot times because changing a granularity value requires rebooting the entire nPartition
as well as recreating the vPars database.
The Goal
The goal to avoid slow boot times is to have the number of granules to be close to 50. Any quantity
up to 100 will show reasonable boot times, but HP recommends a value close to 50.
Example 1
If the total physical memory in the nPartition is 12 GB, then the granularity value should be 256
MB:
12 GB / 256 MB => ~50 granules
Memory: Choosing a Granularity Value and Boot Time (Integrity) 225