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Changing the tunable values using vxvoltune

You can use vxvoltune to display, set, or change the memory tunables that are used by VVR. This utility is used to tune the VxVM tunables as well as the VVR tunables. The advantage of using the vxvoltune utility to tune the parameters is that the changes are persistent. However, it requires you to reboot the system for the changes to take effect.

The vxvoltune utility enables you to modify the values of the following VVR tunables:

vol_rvio_maxpool_sz

vol_min_lowmem_sz

vol_max_rdback_sz

vol_max_nmpool_sz

These tunable values are then updated in the /etc/vx/vxvm_tunables file. After the tunable value has changed you must reboot the system.

 To display the values of specific tunables

Issue the following command on the required host to display the value of the specific tunable:

# vxvoltune tunable_name

This command will display the value of the specified tunable in bytes.

For example, to view the value of the tunable vol_rvio_maxpool_sz issue the following command:

# vxvoltune vol_rvio_maxpool_sz

The output will resemble:

10485760

 To modify the values of the tunables

Issue the following command on the required host to modify the value of the specific tunable:

# vxvoltune tunable_name value

The value value of the tunable can be specified in bytes.

For example, to change the default value of the vol_rvio_maxpool_sz tunable to 131072K, use the following command.

# vxvoltune vol_rvio_maxpool_sz 134217728

To view the changed value for the tunable use the following command:

# vxvoltune vol_rvio_maxpool_sz

  Caution   It is recommended that you do not edit the tunable values directly in the vxvm_tunables file.