Open topic with navigation

Configuring failover monitoring

1. Open the Failover Control Center from your target server or a client machine. Do not run the Failover Control Center from your source server.
2. Select a failover target from the Target Machine list box.

Note:

If the target you need is not listed, click Add Target and manually enter a name or IP address (with or without a port number). You can also select the Browse button to search for a target machine name. Click OK to select the target machine and return to the Failover Control Center main window.

3. Click Login to login to the selected target.
4. Select a source machine to monitor by clicking Add Monitor. The Insert Source Machine dialog box appears in front of the Monitor Settings dialog box.
5. On the Insert Source Machine dialog, specify your source machine by any of the following methods.

• Type the name of the machine that you want to monitor in Machine Name(s) and click OK.
• Click Browse to search for a machine. Select a domain from the list box at the top of the Select Machine dialog box to list the available machines for that domain. Highlight a source to be monitored and click OK.
• Click Custom. Enter the name of the server and click Add. Specify the IP address and subnet mask of the specified server and click OK. Click OK again.

The Insert Source Machine dialog closes and the Monitor Settings dialog remains open with your source listed in the Names to Monitor tree.

6. In the Names to Monitor tree, locate and select the IP addresses on the source that you want to monitor.
7. Highlight an IP address that you have selected for monitoring and select a Target Adapter that will assume that IP address during failover. Repeat this process for each IP address that is being monitored. Current IP Addresses displays the IP address(es) currently assigned to the selected target adapter.
8. Highlight an IP address that you have selected for monitoring and select a Method to Monitor for Failover.

• Network Service—Source availability will be tested for by a Double-Take Availability network response
• Replication Service—Source availability will be tested for by a Double-Take service response.
• Network and Replication—Source availability will be tested for by both a Double-Take Availability network response and a Double-Take service response.
• No Monitoring—Double-Take Availability does not actively monitor the source. You will be responsible for identifying when a failure has occurred and initiating failover manually.

9. Repeat step 8 for each IP address that is being monitored.
10. Highlight an IP address that you have selected for monitoring and select a 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. This option is not configurable if your Method to Monitor for Failover is set to No Monitoring. Repeat this step for each IP address that is being monitored.
11. Highlight an IP address that you have selected for monitoring and select the Missed Packets. 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. This option is not configurable if your Method to Monitor for Failover is set to No Monitoring. Repeat this step for each IP address that is being monitored.

Note:

To achieve shorter delays before failover, use lower Monitor Interval and Missed Packets values. This may be necessary for IP addresses on machines, such as a web server or order processing database, which 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.

12. If you are monitoring multiple IP addresses, highlight the source name and specify the Failover Trigger.

• All Monitored IP Addresses Fail—Failover begins when all monitored IP addresses fail. If there are multiple, redundant paths to a server, losing one probably means an isolated network problem and you should wait for all IP addresses to fail.
• One Monitored IP Address Fails—Failover begins when any one of the monitored IP addresses fails. If each IP address is on a different subnet, you may want to trigger failover after one fails.

13. If Manual Intervention is enabled, Target Data State at Failover will be disabled because the same options will be presented to you at failover time. If Manual Intervention is disabled, the options will be enabled so that an option can be selected to occur automatically when failover occurs. Highlight the source name and specify the Target Data State at Failover by specifying what data you want to use on the target when failover occurs.

• Apply Data in Target Queues Then Failover—All of the data in the target queue will be applied before failover begins. Depending on the amount of data in queue, the amount of time to apply all of the data could be lengthy.
• Discard Data in Target Queues and Failover Immediately—All of the data in the target queue will be discarded and failover will begin immediately. Any data in the target queue will be lost.
• Revert to Last Good Snapshot if Target Data is Bad—If the target data is in a bad Double-Take Availability state, Double-Take Availability will automatically revert to the last good Double-Take Availability snapshot before failover begins. You will lose any data between the last good snapshot and the failure. If the target data is in a good state, Double-Take Availability will not revert the target data. Instead, Double-Take Availability will apply the data in the target queue and then failover. Depending on the amount of data in queue, the amount of time to apply all of the data could be lengthy.

14. Highlight the source name and specify the Items to Failover, which identifies which source components you want to failover to the target.

• IP Addresses—If you want to failover the IP addresses on the source, enable this option and then specify the addresses that you want to failover.
• Monitored—Only the IP address(es) that are selected for monitoring will be failed over.
• All—All of the IP address(es) will be failed over.

Note:

If you are monitoring multiple IP addresses, IP address conflicts may occur during failover when the number of IP addresses that trigger failover is less than the number of IP addresses that are assumed by the target during failover. For example, if a source has four IP addresses (three public and one private), and two of the three public addresses are monitored, but all three public addresses are configured to failover, a conflict could occur. If the source fails, there is no conflict because all of the IP addresses have failed and no longer exist. But if the failure only occurs on one of the monitored addresses, the other two IP addresses are still affected. If all of the addresses are failed over, these addresses then exist on both the source and the target. Therefore, when a source machine has fewer IP addresses that trigger failover than IP addresses that will be failed over, there is a risk of an IP address conflict. If your network environment is a WAN configuration, do not failover your IP addresses unless you have a VPN infrastructure so that the source and target can be on the same subnet, in which case IP address failover will work the same as a LAN configuration. If you do not have a VPN, you can automatically reconfigure the routers via a failover script (by moving the source's subnet from the source's physical network to the target's physical network). There are a number of issues to consider when designing a solution that requires router configuration to achieve IP address failover. Since the route to the source's subnet will be changed at failover, the source server must be the only system on that subnet, which in turn requires all server communications to pass through a router. Additionally, it may take several minutes or even hours for routing tables on other routers throughout the network to converge.

• Server Name—Failover is performed on the server name. If you specify the server name to be failed over, first Double-Take Availability checks the hosts file and uses the first name there. If there is no hosts file, Double-Take Availability uses the first name in DNS. (Although, the first name in DNS may not always be the same each time the DNS server is rebooted.) Lastly, if there is no DNS server, Double-Take Availability uses the Failover Control Center monitor name.
• Shares—Failover is performed on shares.

Note:

Automatic share failover only occurs for standard Windows file system shares. Other shares must be configured for failover through the failover scripts or created manually on the target. See Macintosh shares or NFS Shares for more information. If you are failing over Windows shares but your source and target do not have the same drive letters, you must use the All to One selection when establishing your Double-Take Availability connection. Otherwise, the shares will not be created on the target during failover. If a Windows share is created on Windows 2003 with the default full access permissions (without an ACL) and then failed over, the permissions given to the target will be read-only permissions. Windows share information is automatically updated on the target once an hour. If you need to manually update the share information, click Update Shares on the main Failover Control Center window after the monitor has been established.

15. By default, Manual Intervention is enabled, allowing you to control when failover occurs. When a failure occurs, a prompt appears in the Failover Control Center and waits for you to manually initiate the failover process. Disable this option only if you want failover to occur immediately when a failure occurs. This option is not configurable if the Method to Monitor for Failover is set to No Monitoring.
16. If the Shares selection under Items to Failover is selected, verify that the Use .SHR Share Mapping File check box is selected if you would like to use the Double-Take Availability share mapping file to create shares on the target during failover. If this option is not selected, shares will be created using the information gathered when the machine was selected as a source to be monitored.

Note:

If the Shares selection under Items to Failover is not selected, shares will not be failed over to the target regardless of the Use .SHR Share Mapping File selection.

17. By default, Failover Hostname is disabled. This option automatically removes the host SPN (Service Principle Name) from Active Directory on the source and adds it to Active Directory on the target. If you are using Active Directory, enable this option or you may experience problems with failover.
18. Failback Hostname returns the host SPN on the source and target back to their original settings on failback. If you are using Active Directory, enable this option or you may experience problems with failback.
19. If you are failing over or failing back hostnames, you need to specify an Active Directory user that has update privileges within Active Directory. Click Credentials and identify a user and the associated password that has privileges to create and delete SPNs. The username must be in the format fully_qualified_domain\user. Click OK to return to the Monitor Settings dialog box.

Note:

The Active Directory account password cannot be blank.

20. If you are using any failover or failback scripts, click Scripts and enter the path and filename for each script type. Scripts may contain any valid Windows command, executable, or batch file. Examples of functions specified in scripts include stopping services on the target before failover because they may not be necessary while the target is standing in for the source, stopping services on the target that need to be restarted with the source’s machine name and IP address, starting services or loading applications that are in an idle, standby mode waiting for failover to occur, notifying the administrator before and after failover or failback occurs, stopping services on the target after failback because they are no longer needed, stopping services on the target that need to be restarted with the target machine’s original name and IP address, and so on. Specify each script that you want to run and the following options, if necessary.

• If you want to pass any arguments to your script, specify the arguments.
• If you want to delay the failover or failback processes until the associated script has completed, mark the appropriate check box.
• If you want the same scripts to be used as the default for future monitor sessions, mark the appropriate check box.
• If you want to specify a user account to run the scripts, specify the credentials for the source and target. If no account is specified, the scripts will be processed using the same account that is configured to run the Double-Take service.

21. Click OK to return to the Monitor Settings dialog box.

Note:

Failover scripts will run but will not be displayed on the screen if the Double-Take service is not set to interact with the desktop. Enable this option through the Services applet. With these flexible scripting features, application failover using Double-Take Availability can be seamless to the end user. Double-Take Software tests many of the popular applications on the market today. The results of these testing procedures are written up into formal Application Notes that describe how Double-Take Availability should be configured to work correctly with certain applications, including scripting examples. For a complete list of Double-Take Availability Application Notes, visit the Double-Take Software support web site.

22. Click OK on the Monitor Settings dialog box to save your monitor settings and begin monitoring for a failure.

Related Topics