Search <book_title>...

Storage Foundation 7.4.1 Administrator's Guide - Linux

Last Published: 2019-09-25

Product(s): InfoScale & Storage Foundation (7.4.1)

Platform: Linux

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

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.

By default, the vxtune command only affects the tunable values on the host on which it is run, except for clusterwide tunable parameters. The clusterwide attribute indicates that the vxtune command sets the value for that tunable on all nodes in the cluster. If the tunable parameter is not clusterwide, you can use the -C option to change the tunable values on all nodes of the cluster. If the -C option is used on a standalone system, the operation fails.

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 following example shows a truncated output, that shows the format.

Tunable             Current Value Default Value Reboot Clusterwide  Description
------------------- ------------- ------------- ------ -----------  -----------
vol_checkpt_default         20480         20480      Y           N  Size of VxVM 
																																																																				checkpoints (sectors)
vol_cmpres_enabled              0             0      N           Y  Allow enabling 
																																																																				compression for VERITAS 
																																																																				Volume Replicator
vol_cmpres_threads             10            10      N           N  Maximum number of 
																								                                            compression threads 
																																																																				for VERITAS 
																																																																				Volume Replicator
vol_default_iodelay            50            50      Y           N  Time to pause between
																																																																			 I/O requests from VxVM 
                                                                    utilities (10ms units)
vol_fmr_logsz                   4             4      Y           N  Maximum size of bitmap
                                                                    Fast Mirror Resync 
																																																																				uses to track changed 
                                                                    blocks (KBytes)
vol_max_adminio_poolsz   67108864      67108864      Y           N  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. The Clusterwide field indicates whether vxtune applies the value to all nodes in the cluster by default.

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 [-C] 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
```
If the specified tunable parameter is not clusterwide, use the -C option to set its value for all nodes in the cluster.
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
```
The vxtune command changed the value on all nodes in the cluster, because the vol_cmpres_enabled tunable parameter is clusterwide.