Veritas File System 5.0 AdministratorÆs Guide, HP-UX 11i v3, First Edition, May 2008

Tuning I/O
The performance of a file system can be enhanced by a suitable choice of I/O sizes
and proper alignment of the I/O requests based on the requirements of the
underlying special device. VxFS provides tools to tune the file systems.
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.
VxFS performance: creating, mounting, and tuning file systems
Tuning I/O
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