HP-UX vPars and Integrity VM V6.3 Administrator Guide
following table lists the recommended minimal amount of memory that must be configured as base
memory for some typical memory sizes.
Minimum Base MemoryTotal Guest Memory
1 GB1 GB to 3 GB
1/2 of total memory4 GB to 8 GB
4 GB9 GB to 16 GB
1/4 of total memoryOver 16 GB
WARNING! It is mandatory that the base and floating memory guidelines specified are adhered
to. If the proportion of base to floating memory is too low, the vPar could experience a panic or
hang. The vPar may not boot without sufficient base memory.
NOTE: Some workloads or vPar kernel configurations might require more base memory than
what is recommended here.
The system administrator must configure enough base memory to allow the vPar to achieve required
baseline application performance taking into consideration the following constraints:
• The kernel has more flexibility using base memory. The kernel restricts the use of floating
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 floating 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 might not perform the same as a system configured
with the sufficient amount of base memory prior to booting.
• On a system with heavy amount of memory utilization, the HP-UX kernel might take minutes
or even hours to evacuate memory. Hence, it is advisable not to delete floating memory on a
heavily loaded system.
• Depending on the system load, adding or deleting large amount of floating memory to or
from a live vPar can take significant time. This can sometime result in Serviceguard heartbeat
failures on vPars configured as Serviceguard nodes. HP recommends that a single large
memory transaction be split into multiple smaller transactions.
For example, if a partition contains a large amount of floating memory, instead of deleting
all the floating memory in one operation, it might help to split it into multiple smaller floating
memory delete operations.
NOTE: Under very rare conditions, the kernel could consume some portion of floating memory
during boot. In such a situation, the portion of floating memory consumed by the kernel will be
converted to base memory. When that happens, the guest configuration file will be updated to
reflect the increase in base memory and decrease in floating memory for that vPar.
5.6.3.4 Granularity and memory modification
Granularity refers to the unit size in which memory is assigned to all the vPars. The memory granule
size is fixed at 64 MB. Hence, all memory operations are performed in multiples of this size. On
a live vPar, a maximum of 255 granules can be specified per memory operation. Therefore, the
5.6 Configuring memory for vPars 61