Task 8: Configure Availability Sets

This task is optional. If you have not installed and configured an availability tool, you are not prompted to configure availability sets.

“Task 9: Plan a Service Availability Strategy” described the advance planning that is required to achieve improved availability of services. Planning includes determining the services for which you want to configure improved availability, the nodes you want to associate in availability sets, and special considerations for role assignments on the head node.

The first step to enable improved availability is to define nodes into availability sets now. Keep in mind the default node role assignments and decide on the nodes you want to associate in an availability set.

For example, assume that you have decided that nagios and nat are the services for which you want to enable improved availability. For the purposes of this example, use nodes n7 and n8. Thus, if one of those nodes becomes unavailable, the services fail over to the other node.

When the cluster_config utility prompts you to configure availability sets, you configure nodes n7 and n8 into an availability set and assign node roles accordingly. Using this example, you assign the external and management_server roles to both nodes.

The following criteria must be met to configure improved availability of services:

You have purchased, licensed, installed, and configured an availability tool (such as Serviceguard) .

You have written and positioned tool-specific translator and other related scripts in the /opt/hptc/availability/availability_tool directory.




	NOTE: Scripts for HP Serviceguard were automatically created and positioned for you when you installed the HP XC Serviceguard RPM. You are responsible for writing and positioning these scripts if you are using another availability tool.

As described in “Deciding on the Method to Achieve Quorum for Serviceguard Clusters”, you have configured a lock LUN, or you know which node you plan to use as the quorum server (if using Serviceguard).

Define Availability Sets

If all criteria have been satisfied, the cluster_config utility prompts you to define availability sets, as show in the following procedure.

When the following prompt is displayed, define availability sets:
Cluster Configuration - XC Cluster version HP XC V3.1 <kit> <date> Availability tools: serviceguard (selected) Current availability sets: <none> [E]dit Availability Sets, [P]roceed, [Q]uit:
In this example, only one availability tool has been installed, Serviceguard. Thus, it is the preselected tool which means that any availability set you configure here will be managed by Serviceguard unless you select another availability tool.
Do one of the following:
1. Enter the letter e to create an availability set. Proceed to step 3.
2. Enter the letter p to bypass availability sets and proceed to “Task 9: Assign Node Roles”. You cannot enable improved availability without first configuring at least one availability set.
3. Enter the letter q to exit the cluster_config utility.
  Are you sure you want to quit? [y/n] y

Enter the letter h or the word help to display the list of tasks you can perform:

avail> help
Commands are:
  [l]ist                 - List availability sets
  [s]elect tool          - Select availability tool
  [c]reate node node ..  - Create availability set containing nodes
  [d]elete node          - Delete availability set containing node
  [h]elp                 - Show help
  [b]ack                 - End availability sets, return to cluster_config

Examples:
   select serviceguard
   create n1024 n1023
   delete n1022

Do the following to create an availability set:
1. If more than one availability tool has been installed, select the availability tool that will manage the services in the availability set. If only one tool is available, it is selected by default.
  avail> select serviceguard
2. Create an availability set that will be managed by the selected tool. Specify both node names to associate into the availability set. “Choose Nodes as Members of Availability Sets” described how to choose the nodes to associate in an availability set.
  avail> create n7 n8 Availability Set serviceguard: (n7 n8) created.

Perform these tasks if required:

Delete an availability set by specifying either one of the nodes in the availability set:
avail> delete n7 Availability Set serviceguard: (n7 n8) deleted.

List all availability sets:

avail> list
Availability tools:
  serviceguard (selected)
  
Current availability sets:
  serviceguard: (n7 n8)

When you have finished associating nodes and availability tools into availability sets, enter the letter b or the word back to return to the main availability set menu.
avail> back [E]dit Availability Sets, [P]roceed, [Q]uit:
Do one of the following:
- Enter the letter p if you have finished associating nodes into availability sets. Proceed to step 7.
- Enter the letter e to continue adding or modifying availability sets. Return to step 3.
- Enter the letter q to exit cluster_config utility.
At the following prompt, enter y to continue with the cluster_config utility; enter n to stay in the availability set configuration menu.
Do you want to proceed to roles configuration? [y/n]

Proceed to “Task 9: Assign Node Roles” to evaluate the default node role configuration and re-adjust the default role assignments where necessary.

Task 8: Configure Availability Sets

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Define Availability Sets