Symantec logo

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:

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. For more details,

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

# vxtunefs -p mount_point

The following is an example tunefstab file:

/dev/vx/dsk/userdg/netbackup

read_pref_io=128k,write_pref_io=128k,read_nstream=4,write_nstream=4

/dev/vx/dsk/userdg/metasave

read_pref_io=128k,write_pref_io=128k,read_nstream=4,write_nstream=4

/dev/vx/dsk/userdg/solbuild

read_pref_io=64k,write_pref_io=64k,read_nstream=4,write_nstream=4

/dev/vx/dsk/userdg/solrelease

read_pref_io=64k,write_pref_io=64k,read_nstream=4,write_nstream=4

/dev/vx/dsk/userdg/solpatch

read_pref_io=128k,write_pref_io=128k,read_nstream=4,write_nstream=4