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 2 37
Kernel Tunables
This section describes the kernel tunable parameters in VxFS.
Internal Inode Table Size
VxFS caches inodes in an inode table. There is a dynamic tunable in VxFS called vx_ninode that
determines the number of entries in the inode table.
A VxFS file system obtains the value of vx_ninode from the system configuration file used for making the
HP-UX kernel (/stand/system for example). This value is used to determine the number of entries in the
VxFS inode table. By default, vx_ninode initializes at zero; the file system then computes a value based
on the system memory size. To change the computed value of vx_ninode, you can add an entry to the
system configuration file. For example:
vxfs_inode_table vx_ninode1000000
sets the inode table size to 1,000,000 inodes after making a new HP-UX kernel using mk_kernel. You can
also change the value of vx_ninode by using the sam or kctune commands (see the sam(1M) and
kctune(1M) manual pages).
Increasing the value of vx_ninode increases the inode table size immediately, allowing a higher number of
inodes to be cached. Decreasing the value of vx_ninode decreases the inode table size to the specified
value. After the tunable is decreased, VxFS attempts to free excess cached objects so that the resulting
number of inodes in the table is less than or equal to the specified value of vx_ninode. If this attempt fails,
the value of the vx_ninode tunable is not changed. In such a case, the kctune 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.