System Sizing Guidelines for Integrity Virtual Machines Deployment -- Hardware Consolidation with Integrity Virtual Machines

12
File and Buffer Cache Sizes
By reducing the size of the file cache on the VM Host, the memory overhead of Integrity VM is
reduced significantly, especially for systems with more than 32GB of physical memory. HP
recommends the file cache tunables be set to use less than 128MB of memory:
kctune filecache_max=128000000 filecache_min=128000000
Avoid this configuration on deployments with virtual machines that use a significant number of
virtual disks mapped to files (file backing stores) as it may have significant performance impact.
The filecache_min and filecache_max tunable values must not use alphabetic characters (such as m
or g suffixes) as that will prevent Integrity VM from starting up gracefully.
Another cache that can be reduced on Integrity VM Host system is that of the VxFS metadata buffer
cache. By default, this cache can vary in size dynamically and consume up to 1GB or more of
memory. HP recommends changing this tunable, limiting the amount of memory used by the VxFS
metadata buffer cache to 64MB:
kctune vxfs_bc_bufhwm=64000
It is important to note that the value of this tunable is specified in kilobytes.
Inode Caches
Inode caches on the VM Host system need not be very large due to its using a relatively smaller
number of files. To reduce the size of the HFS inode cache:
kctune ninode=1024
Note that Integrity VM does not support virtual disks mapped to HFS files. Moreover, VxFS is the
default file system for HP-UX and the VxFS inode cache is not controlled by this tunable.
HP also recommends reducing the size of the VxFS inode cache through the following tunable
settings:
kctune vx_ninode=32768 vxfs_ifree_timelag=-1
The VM Host system typically uses very few files when compared to general-purpose HP-UX
systems. As a result, the inode cache for the VM Host system should be significantly smaller than
typical HP-UX systems. The tunable settings above will reduce the VxFS inode cache to the
minimum recommended by HP.
Memory Requirements for the VM Host
Based on the recommendation that the base_pagesize tunable is set to 64 (for 64K page size), the
memory required by the physical VM Host - independent of that required by each virtual machine
deployed - includes 1.2GB plus 8.5% of physical memory. That is:
VM Host memory = 1.2GB + 8.5%  (Total Physical Memory)
Configuring the VM Host system to use base page size other than 64K will cause the VM Host
memory requirement to increase significantly.
Additional Memory Requirement for I/O Adapters on Integrity i2 Servers
The VM Host memory formula above is the minimum required for the HP-UX operating system and
virtualization layer. It does not account for memory needs of certain I/O adapters. For that
reason, one must adjust the VM Host memory accordingly. This results in the actual VM Host
memory requirement being:
VM Host memory = 1.2GB + 8.5% × (Total Physical Memory) + (Memory for I/O Adapters)