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
function queries VxVM when the file system is created to align automatically 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.
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