Top Ten Tips for Using Virtual Partitions

#4 – Memory Granularity and Performance
Symptoms: Performance
Coming up with a suitable granule size
Prevention and Suggestions
If your system (or nPartition) contains a large amount of memory (32 GB or more), you should
consider the following when setting the granularity size:
(a) VM performance: Virtual Memory subsystem in the OS cannot create pages bigger than the
granule size. Run-time performance will be better on systems with higher page size.
(b) Hitting nPar granule limits: Firmware supports certain max number of granules per nPar. If the
system has more memory, granule size should be increased to fit within the limit.
(c) Memory migration flexibility: Smaller granule sizes provide more flexibility in moving the memory
around. So, customers may want to strike a balance between the flexibility and performance needs.
(d) Long time to boot: With smaller granule sizes, vPars were taking a long time to boot on IPF
systems. This problem is addressed by the patch PHKL_35698 in 11iv2 and this is not a problem in
11iv3. PHKL_35698 is part of 1123.0706 FEATURE11i bundle. vPars release A.04.04 requires the
installation of 1123.0706 FEATURE11i bundle.
(e) PA-RISC systems: ILM granule size must be small enough for each vPar to have at least one granule
below 2GB for its memory, plus one granule for the monitor. 1GB granules will be too large for ILM
on PA-RISC systems, therefore, and 128MB or 256MB granules will be better.
Please see the document “Installing and Managing HP-UX Virtual Partitions” for more details.
#5 – Number of vPars and Cells per nPar
Symptoms: Supportability
The current limit regarding the number of vPars and the number of cells per nPar in a vPar’s
environment is 8 for both. So, the current requirement is a maximum of 8 vPars per nPar where the
nPar is a maximum of 8 cells in a vPars environment. The cells may cross SuperDome cabinets, but
the maximum number is 8.
Prevention and Suggestions
Although the vPar software currently allows you to create vPars outside these conditions, you will be
in an unsupported state and may run into problems.
Please see the document “Ordering and Configuration Guide for Virtual Partitions” for more details.
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