8.5. Configuring HA Services

Configuring HA (High Availability) services consists of configuring resources and assigning them to services.
The following sections describe how to edit /etc/cluster/cluster.conf to add resources and services.

Important

There can be a wide range of configurations possible with High Availability resources and services. For a better understanding about resource parameters and resource behavior, see Appendix B, HA Resource Parameters and Appendix C, HA Resource Behavior. For optimal performance and to ensure that your configuration can be supported, contact an authorized Red Hat support representative.

8.5.1. Adding Cluster Resources

You can configure two types of resources:
  • Global — Resources that are available to any service in the cluster. These are configured in the resources section of the configuration file (within the rm element).
  • Service-specific — Resources that are available to only one service. These are configured in each service section of the configuration file (within the rm element).
This section describes how to add a global resource. For procedures about configuring service-specific resources, refer to Section 8.5.2, “Adding a Cluster Service to the Cluster”.
To add a global cluster resource, follow the steps in this section.
  1. Open /etc/cluster/cluster.conf at any node in the cluster.
  2. Add a resources section within the rm element. For example: 
    
    <rm>
        <resources>

        </resources>
    </rm>
  3. Populate it with resources according to the services you want to create. For example, here are resources that are to be used in an Apache service. They consist of a file system (fs) resource, an IP (ip) resource, and an Apache (apache) resource. 
    
    <rm>
        <resources>
           <fs name="web_fs" device="/dev/sdd2" mountpoint="/var/www" fstype="ext3"/>
           <ip address="127.143.131.100" monitor_link="yes" sleeptime="10"/>
           <apache config_file="conf/httpd.conf" name="example_server" server_root="/etc/httpd" shutdown_wait="0"/>
        </resources>
    </rm>
    Example 8.9, “cluster.conf File with Resources Added ” shows an example of a cluster.conf file with the resources section added.
  4. Update the config_version attribute by incrementing its value (for example, changing from config_version="2" to config_version="3").
  5. Save /etc/cluster/cluster.conf.
  6. (Optional) Validate the file against the cluster schema (cluster.rng) by running the ccs_config_validate command. For example: 
    [root@example-01 ~]# ccs_config_validate 
Configuration validates
  7. Run the cman_tool version -r command to propagate the configuration to the rest of the cluster nodes.
  8. Verify that the updated configuration file has been propagated.
  9. Proceed to Section 8.5.2, “Adding a Cluster Service to the Cluster”.

Example 8.9. cluster.conf File with Resources Added 


<cluster name="mycluster" config_version="3">
   <clusternodes>
     <clusternode name="node-01.example.com" nodeid="1">
         <fence>
            <method name="APC">
              <device name="apc" port="1"/>
             </method>
         </fence>
     </clusternode>
     <clusternode name="node-02.example.com" nodeid="2">
         <fence>
            <method name="APC">
              <device name="apc" port="2"/>
            </method>
         </fence>
     </clusternode>
     <clusternode name="node-03.example.com" nodeid="3">
         <fence>
            <method name="APC">
              <device name="apc" port="3"/>
            </method>
         </fence>
     </clusternode>
   </clusternodes>
   <fencedevices>
         <fencedevice agent="fence_apc" ipaddr="apc_ip_example" login="login_example" name="apc" passwd="password_example"/>
   </fencedevices>
   <rm>
       <failoverdomains>
           <failoverdomain name="example_pri" nofailback="0" ordered="1" restricted="0">
               <failoverdomainnode name="node-01.example.com" priority="1"/>
               <failoverdomainnode name="node-02.example.com" priority="2"/>
               <failoverdomainnode name="node-03.example.com" priority="3"/>
           </failoverdomain>
       </failoverdomains>
       <resources>
           <fs name="web_fs" device="/dev/sdd2" mountpoint="/var/www" fstype="ext3"/>
           <ip address="127.143.131.100" monitor_link="yes" sleeptime="10"/>
           <apache config_file="conf/httpd.conf" name="example_server" server_root="/etc/httpd" shutdown_wait="0"/>
        </resources>

   </rm>
</cluster>