HP-UX Virtual Partitions Administrator's Guide (includes A.05.02)

CPU, Memory, and I/O Resources (A.04.xx)
Memory: Choosing a Granularity Value and Boot Time (Integrity)
Chapter 7
253
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.
Example 2
If the total physical memory is 100 GB, then the granularity value should be 2 GB:
100 GB / 2 GB => 50 granules
Note that as seen in “Granularity Issues (Integrity and PA-RISC)” on page 250 and in the vparresources (5)
manpage, memory is allocated to a virtual partition as a multiple of the granularity value. In this example,
given a granularity value of 2 GB, this means that every virtual partition will have at least 2 GB (1 multiple)
allocated to it. Further, this means that any memory assigned between the multiples will be rounded up to
the next multiple. For example, if you attempt to assign 3 GB of memory to a virtual partition, this actual
memory allocated will be rounded up to the next granularity multiple, in this case, of 4 GB.
If having each virtual partition allocated with at least 2 GB of memory is not desired, then you must chose a
granularity value that is less than 2 GB, noting that this will cause the number of granules to be higher than
50 and therefore increase boot time.
NOTE PA-RISC
Due to PA-RISC and Integrity architectural differences, the way memory is presented to
HP-UX on PA-RISC systems is different than on Integrity systems, so PA-RISC systems do not
encounter this slow boot issue.