9.3. Using DRBD in Red Hat Cluster fail-over clusters

[Note]Note

This section deals exclusively with setting up DRBD for Red Hat Cluster fail over clusters not involving GFS. For GFS (and GFS2) configurations, please see Chapter 11, Using GFS2 with DRBD.

This section, like Chapter 8, Integrating DRBD with Pacemaker clusters, assumes you are about to configure a highly available MySQL database with the following configuration parameters:

9.3.1. Setting up your cluster configuration

To configure your highly available MySQL database, create or modify your /etc/cluster/cluster.conf file to contain the following configuration items.

To do that, open /etc/cluster/cluster.conf with your preferred text editing application. Then, include the following items in your resource configuration:

<rm>
  <resources />
  <service autostart="1" name="mysql">
    <drbd name="drbd-mysql" resource="mysql">
      <fs device="/dev/drbd/by-res/mysql/0"
          mountpoint="/var/lib/mysql"
          fstype="ext3"
          name="mysql"
          options="noatime"/>
    </drbd>
    <ip address="10.9.9.180" monitor_link="1"/>
    <mysql config_file="/etc/my.cnf"
           listen_address="10.9.9.180"
           name="mysqld"/>
  </service>
</rm>
[Note]Note

This example assumes a single-volume resource.

Nesting resource references inside one another in <service/> is the Red Hat Cluster way of expressing resource dependencies.

Be sure to increment the config_version attribute, found on the root <cluster> element, after you have completed your configuration. Then, issue the following commands to commit your changes to the running cluster configuration:

ccs_tool update /etc/cluster/cluster.conf
cman_tool version -r <version>

In the second command, be sure to replace <version> with the new cluster configuration version number.

[Note]Note

Both the system-config-cluster GUI configuration utility and the Conga web based cluster management infrastructure will complain about your cluster configuration after including the drbd resource agent in your cluster.conf file. This is due to the design of the Python cluster management wrappers provided by these two applications which does not expect third party extensions to the cluster infrastructure.

Thus, when you utilize the drbd resource agent in cluster configurations, it is not recommended to utilize system-config-cluster nor Conga for cluster configuration purposes. Using either of these tools to only monitor the cluster’s status, however, is expected to work fine.