B.3 Refining the Auto-Failover Policy

You can further refine auto-failover policies to give you more control over if or when an auto-failover occurs. To do this, click the Advanced button to display additional fields for specifying auto-failover criteria and adding monitoring information.

The policy for automatic failover is configured by creating rules. Each row in the Failover Policy Configuration table represents a rule that applies to a single cluster, or to all clusters in the BCC. Each rule contains a set of conditions. Each condition tests one of the following criteria:

These conditions can be combined in any order to construct a more robust rule that helps to avoid an undesired failover. For failover to occur, each condition of only one rule must be satisfied for the specified cluster or clusters.

For example, a rule might contain only one condition that tests whether a connection to a specific cluster has been down for five or more minutes. Failover occurs when peer clusters agree that the connection to the cluster specified in the rule has been down for five or more minutes. If the peer clusters do not agree about the connection being down (that is, one cluster has a valid connection to the specified cluster), failover does not occur. More complex rules can be constructed that contain multiple conditions.

If previously configured, the fields under Failover Policy Configuration should already contain information on the policies that were created in the Cluster Membership Monitoring Settings section of the page.

  1. Under Failover Policy Configuration, select a policy and click Edit to further refine a rule. Click Delete to remove the rule, or click New to create a new rule that you can add the additional failover conditions to.

  2. Select the cluster that you want the rule to apply to, or select All to apply the policy to all clusters.

  3. Under Conditions, choose the type of condition and the appropriate values. To add multiple conditions to the rule, click the Add button below the condition.

    You can use the default setting of Monitor if you don't want to apply the cluster up or cluster down criteria to this policy. You can also specify or change the percent or number of nodes criteria that are used to determine if an auto failover can occur.

  4. Click Apply to save your settings.

For rules with monitor conditions automatically created by using the Cluster Membership Monitoring Settings table, you can add a condition that tests if the connection to the peer cluster is up. Adding this condition changes the behavior of the rule. With this rule, a graceful automatic failover of resources can happen when the connection to the peer cluster is up.

You can also specify or change the criteria for percent or number of nodes that are used to determine if an automatic failover can occur. Do not however use a membership condition of total node failure (either one-hundred percent or the total number of nodes); the condition can't be satisfied, because the cluster won't be up to report this state. Also, adding a connection down condition to a rule with a condition that tests cluster membership is not recommended. It is highly unlikely that cluster membership information for a specific cluster will be reported to peer clusters when the connection to that specific cluster is down. For these reasons, you should create a separate rule with a connection down condition.