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 |
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.
To change the values of the VxVM tunable parameters
# 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.
# 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.
# 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.