Veritas File System 5.1 SP1 Administrator"s Guide (5900-1499, April 2011)
command can be specified with the -h option so that the new value of vx_ninode
takes effect after a system reboot.
Be careful when changing the value of vx_ninode, as the value can affect file
system performance. Typically, the default value determined by VxFS based on
the amount of system memory ensures good system performance across a wide
range of applications. However, if it is determined that the default value is not
suitable, vx_ninode can be set to an appropriate value based on the expected file
system usage. The vxfsstat command can be used to monitor inode cache usage
and statistics to determine the optimum value of vx_ninode for the system.
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.
Decreasing the value of vx_ninode will not succeed if the doing so requires a
change to internal hash tables, in which case the change is marked for the next
boot automatically and will take effect on the subsequent boot. If the change to
the internal hash tables is not required, VxFS frees the cached objects so that the
total number of inodes in the cache is equal to or less than the specified vx_ninode
value.
Examples of changing the vx_inode tunable value
The following are examples of changing the vx_ninode tunable value.
Reporting the current value of vx_ninode
# kctune vx_ninode
This command displays the current value of vx_ninode.
Setting vx_ninode
# kctune -s vx_ninode=10000
This command sets vx_ninode to 10000, the specified value.
Restoring vx_ninode to its default value
# kctune -s vx_ninode=
VxFS performance: creating, mounting, and tuning file systems
Tuning the VxFS file system
46