Top Ten Tips for Using Virtual Partitions

Prevention and Suggestions
In vPars releases prior to A.04 the only way to increase the I/O interrupt processing is to add
additional bound CPUs. This does require a reboot of the vPar that is changing.
In vPars A.04 and A.05, all vPars start out able to handle I/O interrupt processing. However when
CPUs are deleted online, interrupts are migrated out. But when CPUs are added online, interrupts
are not automatically redistributed. With A.04 and A.05 you can issue the HP-UX command “inctl”
to move interrupts from over-utilized CPUs to under-utilized CPUs.
Please see the whitepaper called “CPU Configuration Guidelines for vPars” for more details.
#8 – Memory Overhead with vPars
Symptoms: Performance, Functionality
The last vPar loaded on IPF systems has around 512MB of memory missing. Why is the last vPar
short memory?
Prevention and Suggestions
On PA-RISC the vPar monitor and database simply reside in memory and take up around 20-25MB of
memory one time regardless of the number of vPars. You will see the last vPar loaded short this 20-
25MB.
On Itanium the vPar memory overhead is quite a bit more compared to PA-RISC. When the mode is
changed to vPar, the vPar’s monitor and supporting firmware needs a certain amount of memory to
load itself and allocate its data structures. The total amount of memory taken is 384MB when the
monitor is launched.
The memory required for each firmware instance associated with each vPar is typically around 32MB
(and may be little more). And in addition, firmware takes away 64MB from each cell. Please note
that this 64MB from each cell is also taken when in nPar mode and is not vPar specific.
So by the time you are done, the last vPar loaded may see as much as 512MB of missing. It will
always be the last vPar loaded due to how the vPar monitor gives out memory as it loads the vPars in
the order they are in the vPar database.
#9 – vPars and Securepath
Symptoms: Performance, Supportability
After installing Securepath the disk array LUNs under Securepath control will be claimed by hsx driver
and it will no longer be possible to retrieve the EFI path to each device, i.e. neither 'ioscan -e' nor
'vparefiutil' will show EFI paths for these LUNs.
Prevention and Suggestions
When installing vPars A.04.01 on an IPF system which will also use Securepath the following
installation procedure must be used:
• Install HP-UX
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