Reconfiguring vPars v6 memory with zero downtime
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Allowed memory modication operations
The table below summarizes what you can do with each type of memory.
vPar state Base Memory Floating Memory
ADD DELETE ADD DELETE
Online Allowed Not Allowed Allowed Allowed
Oine Allowed Allowed Allowed Allowed
Base and oating memory conguration guidelines
The following provides some guidelines on how to use base and oating memory in a vPar.
• The HP-UX kernel requires a certain percentage of total memory to be base memory for system performance and to
ensure that there is adequate memory available for critical system needs. The following table shows the recommended
minimal amount of memory that must be congured as base memory for some typical memory sizes. Some workloads
may require more base memory than what is recommended here.
Total Guest Memory Minimum Base Memory
1 GB to 2 GB 1 GB
2 GB to 8 GB 1/2 of total memory
8 GB to 16 GB 4 GB
Over 16 GB 1/4 of total memory
WARNING
It is mandatory that the base and oating memory guidelines specied are adhered to. If the proportion of base to
oating memory is too low, the vPar could experience a panic or hang.
• The system administrator needs to congure enough base memory to allow the vPar to achieve required baseline
application performance taking into consideration the following constraints:
– The kernel has more exibility using base memory. The kernel restricts the use of oating memory to contents that
it can later relocate if necessary. Hence, a system with all base memory would perform better compared to a system
with the same amount of memory for system use but divided between base and oating memory.
– Some kernel sub-systems and applications do their allocations based on the amount of base memory discovered
at system boot time. These subsystems or applications could allocate their caches based on the amount of base
memory available to the kernel during boot time and might not scale that cache when more base memory is made
available later through online memory addition. Hence, the performance of a system that is booted with less base
memory followed by online addition of base memory may not perform equally to a system congured with the
sucient amount of base memory prior to booting.
Technical white paper | HP-UX vPars and Integrity VM v6.2