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Configuring failover monitoring

1. Make sure you have a valid domain and servers specified, click Configure from the main Application Manager page, and then select the Monitoring tab.
2. To enable the target to monitor the source for a failure, enable Active Monitoring Enabled. If this option is disabled, you will need to manually monitor the source and initiate failover if the source fails.
3. To help you better control when failover occurs, enable Manual Intervention Required. If this option is disabled, failover will occur immediately when a failover condition is met.

4. Specify the following Monitor Settings.

   

• Method to Monitor for Failover—You have three choices for having the target monitor the source for a failure.
  • Network Access—ICMP pings are used to determine if the source is online. Network devices, such as firewalls or routers, must have ICMP pings unblocked in order to use this option.
  • Replication Service—The Double-Take service on the target sends a UDP request to the source, which replies immediately to confirm it is online. Use this method if ICMP pings are blocked.
  • Application Monitoring—In non-cluster environments, you can monitor an application via a monitoring script. The script can be WMI, PowerShell, Visual Basic, or JScript.
• Monitor Interval—This setting identifies the number of seconds between the monitor requests sent from the target to the source to determine if the source is online. The default setting depends on the Method to Monitor for Failover.

• Failure Count—This setting is the number of monitor replies sent from the source to the target that can be missed before assuming the source machine has failed. The default setting depends on the Method to Monitor for Failover.

  To achieve shorter delays before failover, use lower Monitor Interval and Failure Count values. This may be necessary for IP addresses on servers that must remain available and responsive at all times. Lower values should be used where redundant interfaces and high-speed, reliable network links are available to prevent the false detection of failure. If the hardware does not support reliable communications, lower values can lead to premature failover. To achieve longer delays before failover, choose higher values. This may be necessary for IP addresses on slower networks or on a server that is not transaction critical. For example, failover would not be necessary in the case of a server restart. Additionally, in a cluster environment, you must take into account the time it will take for a virtual server to failover between nodes.

   

• Monitored IPs—Mark the IP addresses on the source that you want the target to monitor.
• Failover Trigger—Specify if you want failover to be triggered when all monitored IP addresses fail or if only one of the monitored IP addresses fail.
• Application Monitoring Settings—If you selected Application Monitoring as your Method to Monitor for Failover, you need to configure the script that will monitor your application.
  • Credentials—Specify a user with access to run the application monitoring script on the target. The user name must be a fully qualified name in the format domain\username or username@domain. If you are using the Built-In Monitoring script, the user must have full WMI access to the CIMV2 namespace. By default, the administrative group on Windows 2008 has full WMI access. If you are using Windows 2008, the user must be allowed through DCOM and User Access Control.
  • Monitoring Option—You have a choice of two monitoring methods.
    • Built-In Monitoring—Double-Take Availability will monitor the application using WMI. Specify if you want Double-Take Availability to Attempt to restart services if the application services are not responding.

    • Customer Monitoring Script—Click Browse to locate your own custom script that will monitor the application. The custom script can be PowerShell, Visual Basic, or JScript. Once your script is identified, you can click Edit to open a text editor to view or modify the script.

      A sample Visual Basic script for application monitoring is available in the \Application Manager\Samples subdirectory where Double-Take Availability is installed.

      If you are using a PowerShell script, PowerShell must be installed on the target.

       

5. Click OK to save the settings.