Changing the values of the Veritas Volume Manager tunable parameters using the vxtune command line


Changing the values of the Veritas Volume Manager tunable parameters using the vxtune command line
Prev	Methods to change Veritas Volume Manager tunable parameters	Next

Use the vxtune command to display or change the values of the VxVM tunable parameters. The changes are persistent so that the value is retained after subsequent reboots. Before setting a new value, VxVM validates the value to ensure that it is within the permissible range for the tunable. If the value is valid, VxVM updates the tunable. Some tunables require a reboot before the changed value takes effect. VxVM prompts you to reboot the system, if required.

VxVM stores the tunable values in the /etc/vx/vxtunables file.

Caution:

The recommended method to change the tunable values is with the vxtune command. Do not edit the tunable values directly in the vxtunables file.

For most tunables, specify the value of the tunable with a suffix to indicate the units: K, M, or G. If no unit is specified, vxtune assumes the value is bytes.

Note:

The default unit for entering a value may differ from the default display unit.

To change the values of the VxVM tunable parameters

Find the name and current value of the tunable you want to change. Use the -l option to display a description.

# vxtune -l

The format of the output is similar to the following:

Tunable             Current Value Default Value Reboot Description
------------------- ------------- ------------- ------ -----------
vol_checkpt_default         20480         20480      Y Size of VxVM checkpoints (sectors)
vol_cmpres_enabled              0             0      N Allow enabling compression for 
                                                       VERITAS Volume Replicator
vol_cmpres_threads             10            10      N Maximum number of compression 
                                                       threads for VERITAS Volume Replicator
vol_default_iodelay            50            50      Y Time to pause between I/O requests 
                                                       from VxVM utilities (10ms units)
vol_fmr_logsz                   4             4      Y Maximum size of bitmap Fast Mirror
                                                       Resync uses to track changed blocks
                                                       (KBytes)
vol_max_adminio_poolsz   67108864      67108864      Y Maximum amount of memory used by 
                                                       VxVM admin IO's (bytes)
.
.
.

The output displays the default value and the current value. The Reboot field indicates whether or not a reboot is required before the tunable value takes effect.

See the vxtune(1M) manual page.

Set the new value for a specific tunable. Specify the value with a suffix to indicate the units: K, M, or G. If not unit is specified, the vxtune command uses the default unit for the tunable parameter. For most tunables, the default value is bytes. The description in the vxtune output displays the default units for each tunable.
```
# vxtune tunable_name tunable_value
```
For example, to change the value of vol_cmpres_enabled to 1, use the following command:
```
# vxtune vol_cmpres_enabled 1
```
For example, to change the default value of the vol_rvio_maxpool_sz tunable to 160MB, use the following command.
```
# vxtune vol_rvio_maxpool_sz 160M
```

Verify the new value.

# vxtune tunable_name

For example, to view the changed value for vol_cmpres_enabled, use the following command:

# vxtune vol_cmpres_enabled
Tunable              Current Value Default Value Reboot
-------------------- ------------- ------------- ------
vol_cmpres_enabled   1             0             N

For example, to view the changed value for the vol_rvio_maxpool_sz tunable parameter, use the following command:

# vxtune vol_rvio_maxpool_sz 
Tunable              Current Value Default Value Reboot
-------------------- ------------- ------------- ------
vol_rvio_maxpool_sz  167772160     134217728     N

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