6.7. Configuring Fencing for Cluster Members

Once you have completed the initial steps of creating a cluster and creating fence devices, you need to configure fencing for the cluster nodes. To configure fencing for the nodes after creating a new cluster and configuring the fencing devices for the cluster, follow the steps in this section. Note that you must configure fencing for each node in the cluster.

Note

It is recommended that you configure multiple fencing mechanisms for each node. A fencing device can fail due to network split, a power outage, or a problem in the fencing device itself. Configuring multiple fencing mechanisms can reduce the likelihood that the failure of a fencing device will have fatal results.
This section documents the following procedures:

6.7.1. Configuring a Single Power-Based Fence Device for a Node

Use the following procedure to configure a node with a single power-based fence device. The fence device is named my_apc, which uses the fence_apc fencing agent. In this example, the device named my_apc was previously configured with the --addfencedev option, as described in Section 6.5, “Configuring Fence Devices”.
  1. Add a fence method for the node, providing a name for the fence method.
    ccs -h host --addmethod method node
    For example, to configure a fence method named APC for the node node-01.example.com in the configuration file on the cluster node node-01.example.com, execute the following command:
    ccs -h node01.example.com --addmethod APC node01.example.com
    
  2. Add a fence instance for the method. You must specify the fence device to use for the node, the node this instance applies to, the name of the method, and any options for this method that are specific to this node:
    ccs -h host --addfenceinst fencedevicename node method [options]
    
    For example, to configure a fence instance in the configuration file on the cluster node node-01.example.com that uses power port 1 on the APC switch for the fence device named my_apc to fence cluster node node-01.example.com using the method named APC, execute the following command:
    ccs -h node01.example.com --addfenceinst my_apc node01.example.com APC port=1
    
You will need to add a fence method for each node in the cluster. The following commands configure a fence method for each node with the method name APC. The device for the fence method specifies my_apc as the device name, which is a device previously configured with the --addfencedev option, as described in Section 6.5, “Configuring Fence Devices”. Each node is configured with a unique APC switch power port number: The port number for node-01.example.com is 1, the port number for node-02.example.com is 2, and the port number for node-03.example.com is 3.
ccs -h node01.example.com --addmethod APC node01.example.com
ccs -h node01.example.com --addmethod APC node02.example.com
ccs -h node01.example.com --addmethod APC node03.example.com
ccs -h node01.example.com --addfenceinst my_apc node01.example.com APC port=1
ccs -h node01.example.com --addfenceinst my_apc node02.example.com APC port=2
ccs -h node01.example.com --addfenceinst my_apc node03.example.com APC port=3
Example 6.2, “cluster.conf After Adding Power-Based Fence Methods ” shows a cluster.conf configuration file after you have added these fencing methods and instances to each node in the cluster.

Example 6.2. cluster.conf After Adding Power-Based Fence Methods


<cluster name="mycluster" config_version="3">
   <clusternodes>
     <clusternode name="node-01.example.com" nodeid="1">
         <fence>
            <method name="APC">
              <device name="my_apc" port="1"/>
             </method>
         </fence>
     </clusternode>
     <clusternode name="node-02.example.com" nodeid="2">
         <fence>
            <method name="APC">
              <device name="my_apc" port="2"/>
            </method>
         </fence>
     </clusternode>
     <clusternode name="node-03.example.com" nodeid="3">
         <fence>
            <method name="APC">
              <device name="my_apc" port="3"/>
            </method>
         </fence>
     </clusternode>
   </clusternodes>
   <fencedevices>
         <fencedevice agent="fence_apc" ipaddr="apc_ip_example" login="login_example" name="my_apc" passwd="password_example"/>
   </fencedevices>
   <rm>
   </rm>
</cluster>
Note that when you have finished configuring all of the components of your cluster, you will need to sync the cluster configuration file to all of the nodes, as described in Section 6.15, “Propagating the Configuration File to the Cluster Nodes”.