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. You can set the value to any integer between one and the number of operational nonprimary 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 Concepts for Oracle Solaris Cluster 4.4 for more information.
If you change the numsecondaries property, secondary nodes are added or removed from the device group if the change causes a mismatch between the actual number of secondaries and the desired number.
This procedure uses the clsetup utility to set the numsecondaries property for all types of device groups. Refer to the cldevicegroup(8CL) man page for information about device group options when configuring any device group.
The phys-schost# prompt reflects a global-cluster prompt. Perform this procedure on a global cluster.
The Main Menu is displayed.
The Device Groups Menu is displayed.
The Change Key Properties Menu is displayed.
Follow the instructions and type the desired number of secondaries to be configured for the device group. The corresponding cldevicegroup command is then executed, a log is printed, and the utility returns to the previous menu.
# cldevicegroup show dg-schost-1 === Device Groups === Device Group Name: dg-schost-1 Type: Local_Disk failback: yes Node List: phys-schost-1, phys-schost-2, phys-schost-3 preferenced: yes numsecondaries: 1 diskgroup names: dg-schost-1
Look for the device group information that is displayed by the following command.
# cldevicegroup show -v devicegroup
The following example shows the cldevicegroup command that is generated by clsetup when it configures the desired number of secondaries for a device group (dg-schost-1). This example assumes that the disk group and volume were created previously.
# cldevicegroup set -p numsecondaries=1 dg-schost-1 # cldevicegroup show -v dg-schost-1 === Device Groups === Device Group Name: dg-schost-1 Type: SVM failback: yes Node List: phys-schost-1, phys-schost-2 preferenced: yes numsecondaries: 1 diskset names: dg-schost-1Example 36 Setting the Desired Number of Secondaries to the Default Value
The following example shows use of a null string value to configure the default number of secondaries. The device group will be configured to use the default value, even if the default value changes.
# cldevicegroup set -p numsecondaries= dg-schost-1 # cldevicegroup show -v dg-schost-1 === Device Groups === Device Group Name: dg-schost-1 Type: SVM failback: yes Node List: phys-schost-1, phys-schost-2 phys-schost-3 preferenced: yes numsecondaries: 1 diskset names: dg-schost-1