Veritas File System 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

VxFS Performance: Creating, Mounting, and Tuning File Systems
Kernel Tunables
Chapter 238
Changing the value of a tunable does not resize the internal hash tables and structures of the caches. These
sizes are determined at system boot up based on either the system memory size, which is the default, or the
value of the tunable if explicitly set, whichever is larger. Thus, dynamically increasing the tunable to a value
that is more than two times either the default value or the user-defined value, if larger, may cause
performance degradation unless the system is rebooted.
Examples of Changing the vx_inode Tunable Value
The following are examples of changing the vx_ninode tunable value.
Example 1 - Reporting the Current Value of vx_ninode
# kctune vx_ninode
This command displays the current value of vx_ninode.
Example 2 - Setting vx_ninode
# kctune -s vx_ninode=10000
This command sets vx_ninode to 10000, the specified value.
Example 3 - Restoring vx_ninode to Its Default Value
# kctune -s vx_ninode=
This command restores vx_ninode to its default value by clearing the user-specified value. The default
value is the value determined by VxFS to be optimal based on the amount of system memory, which is used
if vx_ninode is not explicitly set.
Example 4 - Delaying a Change to vx_ninode Until After a Reboot
# kctune -h -s vx_ninode=10000
If the -h option is specified, the specified value for vx_ninode will not take effect until after a system
reboot.
VxFS Buffer Cache High Water Mark
VxFS maintains its own buffer cache in the kernel for frequently accessed file system metadata. This cache
is different from the HP-UX kernel buffer cache that caches file data. The vx_bc_bufhwm global tunable
parameter lets you change the VxFS buffer cache high water mark, that is, the maximum amount of memory
that can be used to cache VxFS metadata.