Veritas File System 5.0 Administrator's Guide (September 2006)

Note: The following tunables and the techniques work on a per file system basis.
Use them judiciously based on the underlying device properties and characteristics
of the applications that use the file system.
Tuning VxFS I/O parameters
VxFS provides a set of tunable I/O parameters that control some of its behavior.
These I/O parameters are useful to help the file system adjust to striped or RAID-5
volumes that could yield performance superior to a single disk. Typically, data
streaming applications that access large files see the largest benefit from tuning
the file system.
VxVM queries
VxVM receives the following queries during configuration:
The file system queries VxVM to determine the geometry of the underlying
volume and automatically sets the I/O parameters.
Note: When using file systems in multiple volume sets, VxFS sets the VxFS
tunables based on the geometry of the first component volume (volume 0) in
the volume set.
The mount command queries VxVM when the file system is mounted and
downloads the I/O parameters.
If the default parameters are not acceptable or the file system is being used without
VxVM, then the /etc/vx/tunefstab file can be used to set values for I/O
parameters. The mount command reads the /etc/vx/tunefstab file and downloads
any parameters specified for a file system. The tunefstab file overrides any values
obtained from VxVM. While the file system is mounted, any I/O parameters can
be changed using the vxtunefs command which can have tunables specified on
the command line or can read them from the /etc/vx/tunefstab file.
See the vxtunefs(1M) and tunefstab(4) manual pages.
The vxtunefs command can be used to print the current values of the I/O
parameters.
To print the values, type the following command:
# vxtunefs -p mount_point
The following is an example tunefstab file:
VxFS performance: creating, mounting, and tuning file systems
Tuning I/O
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