Veritas Storage Foundation™ for Oracle 5.0.1 Administrator's Guide

and running the extent fragmentation report feature of fsadm before and after
the reorganization.
The “before” result is the degree of fragmentation prior to the reorganization. If
the degree of fragmentation approaches the percentages for bad fragmentation,
reduce the interval between fsadm. If the degree of fragmentation is low, increase
the interval between fsadm runs.
How tuning VxFS I/O parameters works
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 far superior to a single disk. Typically, data
streaming applications that access large files see the biggest benefit from tuning
the file system.
If VxFS is being used with Veritas Volume Manager, the file system queries VxVM
to determine the geometry of the underlying volume and automatically sets the
I/O parameters. VxVM is queried by mkfs when the file system is created to
automatically align the file system to the volume geometry. If the default alignment
from mkfs is not acceptable, the -o align=n option can be used to override
alignment information obtained from VxVM. The mount command also 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.
The vxtunefs command can be used to print the current values of the I/O
parameters.
See the vxtunefs(1M) and tunefstab(4) manual pages.
About tunable VxFS I/O parameters
The following are tunable VxFS I/O parameters:
The preferred read request size. The file system uses this
parameter in conjunction with the read_nstream value
to determine how much data to read ahead. The default
value is 64K.
read_pref_io
303Tuning for performance
About tuning VxFS