Christian Bilien's Oracle performance and tuning blog

HP-UX vpar memory: granule size matters


Memory is normally assigned to vPars in units called granules (although the vparcreate/vparmodify commands specify memory in multiples of 1MB, the vPar monitor will round up to the next multiple of granule size). As the granule size is specified when the vPar database is created and can not be changed without recreating the virtual partitions database, care must be taken to choose an appropriate granule size when the first vpar is created. Since this is a fairly complex subject, I thought the rules would deserve a note.


Each vPar will require one ILM granule below 2GB to load its kernel. vpmon uses one granule below 2GB. Therefore (2GB ÷ granule size) -1 = maximum number of vPars. For example, 7 is the maximum number of vPars for an ILM granule size of 256MB (2GB ÷256MB -1 = 7).

Integrity (Itanium)

There is a platform dependent maximum to the number of granules of CLM/cell and of ILM per nPar. These values can be displayed using the vparenv command. Remember that Memory Size ÷ Granule size <= maximum # of granules.



# vparenv

vparenv: The next boot mode setting is “vPars”.
vparenv: The ILM granule size setting is 128.
vparenv: The CLM granule size setting is 128.
vparenv: Note: Any changes in the above settings will become effective only after the next system reboot.
vparenv: Note: The maximum possible CLM granules per cell is 512.
vparenv: Note: The maximum possible ILM granules for this system is 1024

Given the values above the total amount of CLM per cell must be less than 64GB (512 * 128MB) and the total amount of ILM in the nPar must be less than 128GB (1024*128 MB) .

Matching firmware and vpar granule size (Integrity only)

On Integrity systems the memory is divided into granules by the firmware. It is critical that the firmware value for the granule size matches the size in the vPars database. You can examine and modify the firmware setting using the vparenv command. For PA-RISC systems the memory is divided by granules by the monitor and there is no firmware setting. . You can ensure the firmware is updated with the same size as the database by specifying the y option: : vparcreate -g ilm:Mbytes:y –g clm:Mbytes:y. I am not sure what use can be made of diverging granule sizes.