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 receives the following queries during configuration:
mkfs
when the file system is created to align automatically the file system to the volume geometry.
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. 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.
The following is an example tunefstab
file:
read_pref_io=128k,write_pref_io=128k,read_nstream=4,write_nstream=4
read_pref_io=128k,write_pref_io=128k,read_nstream=4,write_nstream=4
read_pref_io=64k,write_pref_io=64k,read_nstream=4,write_nstream=4
read_pref_io=64k,write_pref_io=64k,read_nstream=4,write_nstream=4
read_pref_io=128k,write_pref_io=128k,read_nstream=4,write_nstream=4