The numsecondaries property specifies the number of nodes within a device group that can master the group if the primary node fails. The default number of secondaries for device services is one. The value can be set to any integer between one and the number of operational non-primary provider nodes in the device group.
This setting is an important factor in balancing cluster performance and availability. For example, increasing the desired number of secondaries increases the device group's opportunity to survive multiple failures that occur simultaneously within a cluster. Increasing the number of secondaries also decreases performance regularly during normal operation. A smaller number of secondaries typically results in better performance, but reduces availability. However, a larger number of secondaries does not always result in greater availability of the file system or device group in question. Refer to Chapter 3, Key Concepts for System Administrators and Application Developers, in Sun Cluster Concepts Guide for Solaris OS for more information.
Become superuser on any node of the cluster.
Run the scsetup(1M) utility.
The Main Menu is displayed.
To work with VxVM disk device groups, type 4 (Device groups and volumes).
The Device Groups Menu is displayed.
To change key properties of a device group, type 6 (Change key properties of a device group).
The Change Key Properties Menu is displayed.
To change the desired number of secondaries, type 2 (Change the numsecondaries property).
Follow the instructions and type the desired number of secondaries to be configured for the disk device group. After an appropriate value has been typed, the corresponding scconf command is executed. Following, a log is printed, and the user is returned to the previous menu.
Validate the device group configuration by using the scconf -p command.
# scconf -p | grep Device Device group name: dg-schost-1 Device group type: VxVM Device group failback enabled: yes Device group node list: phys-schost-1,phys-schost-2, phys-schost-3 Device group ordered node list: yes Device group desired number of secondaries: 1 Device group diskset name: dg-schost-1
If you change any configuration information for a VxVM disk group or volume that is registered with the cluster, you must reregister the disk device group by using scsetup. Such configuration changes include adding or removing volumes, as well as changing the group, owner, or permissions of existing volumes. Reregistration after configuration changes ensures that the global namespace is in the correct state. See How to Update the Global Device Namespace.
Verify the primary node and status for the disk device group.
# scstat -D
The following example shows the scconf command that is generated by scsetup when it configures the desired number of secondaries for a device group (diskgrp1). See How to Change the Desired Number of Secondaries for a Device Group for information about changing the desired number of secondaries after a device group is created.
# scconf -a -D type=vxvm,name=diskgrp1,nodelist=host1:host2:host3\ ,preferenced=true,failback=enabled,numsecondaries=2