Disaster Recovery Software
Double-Take For Windows Servers

The following page will describe setting up a Disaster Recovery Software solution for Windows servers using DoubleTake software.

DoubleTake is the market leader for mirroring software for the following reasons:

• Once the servers are mirrored, Double-Take will only update byte level changes in data instead of updating whole blocks or files. This means that keeping your servers mirrored will have little effect on network performance and allows replication over a WAN or VLAN.
• DoubleTake also allows for the secondary server to automatically assume the identity and role of a failed server while maintaining the availability services, daemons, NLMs or applications with minimal disruption or data loss.
• DoubleTake runs at the kernel level so it can replicate data written by any application.
• By using page files DoubleTake can replicate changes in open files enabling up-to-the-second data mirroring.

You can download an evaluation copy from here : Download Page

Steps for Server Mirroring, Replication and Failover

Install Software on the Source Server

1. Install your application software on the source server. (if not already installed)
2. Record the location where the application is stored.
3. Install DoubleTake on the source server using installation defaults (see DoubleTake Gettind Started guide for details).

Install and Configure Software on the Target

1. Install your application software using the same locations recorded previously.
2. On the target server, set the application service, daemon, or NLM to manual startup. (This allows the failover and failback scripts you be creating to run)
3. Install DoubleTake on the target server using installation defaults (see DoubleTake Gettind Started guide for details).

Configure DoubleTake and Begin Mirroring

The next two sections use the Management Console and Failover Control Center to configure Double-Take and failover. To use the Double-Take Text Client, reference Double-Take's User's Guide.

1. Select Start, Programs, Double-Take, Management Console.
2. Double-click your source machine to log on.
3. Right-click the source machine and select Properties.
4. Select the Startup tab.
   
   
   
   
   
5. By default. Perform Remirror After Auto-Reconnect will be selected. Disable this options so that the source does not remirror files after failback. If this option is selected, the source will remirror files and potentially overwrite newer files on the target machine. Click OK to continue.
6. Right-click your source machine and select New, Replication Set and enter the desired name for the replication set.
7. Select the data you wish to protect. Review the locations you recorded for your application software. Be sure and select all locations where the application's data files, such as database or log files, are stored.
   
   NOTE: It is not necessary to replicate the application's executable files since they already exist on the target machine. 8 Right-click the replication set name and select Save to save the replication set.
   
   
   
   
   
8. Right-click the replication set name and select Save to save the replication set.
9. Drag and drop the replication set onto the target. The Connection Manager dialog box opens.
   
   
   
   
   
10. The Source Server, Target Server, Replication Set, and Route fields will automatically be populated. If you have multiple IP addresses on your target, verify the Route field is set to the correct network path. (For detailed information on establishing a connection, see Double-Take's User's Guide).
11. Select the One To One mapping so that the replication set data is transmitted to the same directory structure on the target.
12. Click Connect to start the mirror and replication processes.

Configure Failover and Begin Failure Monitoring

1. If a failure occurs, you will want to have the application software on the target machine automatically- To do this, create a batch file called postover.bat that starts your application software. Save the batch file to the same directory where your Double-Take files are installed. (For detailed information on starting your application software manual, see the application's reference guide).
   
   POSTOVER.BAT
   
   rem Sample post-failover batch file for SQL 7.0 running on Windows 2000.
   net start "Distributed Transaction Coordinator"
   net start "Message Queuing"
   net start "MSSQLServer"
   net start "SQLServerAgent"
   
   NOTE: Sample batch files are provided for each operating system in Double-Take User's Guide.
   
   
2. After a failure is resolved, you will he ready to bring your source back online. You will want to stop the application software on the target automatically. To do this. create a batch file called preback.bat that stops your application software. Save the batch file to the same directory where your Double-Take files are installed. (For detailed information on stopping your application software manual, see the application's reference guide).
   
   PREBACK.BAT
   
   rem Sample pre-failback batch file for SQL 7.0 running on Windows 2000.
   net stop "Distributed Transaction Coordinator"
   net stop "Message Queuing"
   net stop "MSSQLServer"
   net stop "SQLServerAgent"
   
   
3. Select Start, Programs, Double-Take, Faiiover Control Center.
4. Select the target machine from the list of available machines. If the target you need is not displayed, click Add Target, enter the machine name, and click OK.
5. To add a monitor for the selected target, click Add Monitor. Type the name of the source machine and click OK. The Monitor Settings window will open.
6. In the Monitor Settings window, mark the IP address that is going to failover and verify that Adding Source Identity to Target is selected.
   
   
   
   
   
7. Click Scripts and specify the location and file names of the scripts that were created in steps 1 and 2.
   
   
   
   
   
8. Click OK to go back to the Monitor Settings dialog box.
9. Click OK to begin monitoring the source machine.

In the event of a source machine failure, your target machine is now ready to stand in for your source.

Monitoring Failover

Now that replication and failover monitoring are configured and started, you will need to know if and when there is a problem. Since it can be essential to quickly know the status of your machines, Double-Take offers various methods for monitoring the status of failover. When the Failover Control Center is running, you will see four visual indicators:

• The Failover Control Center Time to Fail countdown
• The Failover Control Center -status bar located at the bottom of the window
• The Failover Control Center coloured bullets to the left of each IP address and source machine
• The Windows desktop icon tray containing a failover icon
  

NOTE: You can minimize the Failover Control Center and, although it will not appear in your Windows taskbar, it will still be active and the failover icon will still appear in the desktop icon tray.
The Failover Control Center does not have to be running for failover to occur.

The following table identifies how the visual indicators change as the status of faitover changes.

*When the Time to Fail value has decreased by 25 of the entire timeout period, the bullet changes from green to yellow, indicating that the target has not received a response from the source. The yellow bullet is a caution signal. If a response from the source is received, the countdown resets and the bullets change back to green. If the countown reaches zero without the target receiving a response from the source, failover begins.

Once failover is complete, any clients logging into the Exchange server will be automatically directed to the target. Depending on the type of client software being used. Exchange clients with an exsiting connection may have to be restarted in order to establish a connection with the target.

NOTE: For additional detailed information on failover and other monitoring tools, see Double-Take's User's Guide.

Restoring Your Data

If your source experiences a failure, such as a power, network, or disk failure, your target machine will stand in for the source while you resolve the source machine issues. During the source machine downtime, data is updated on the target machine. When your source machine is ready to come back online, the data is no longer current and must be updated with the new data on the target machine.

1. Verify that your source machine is not connected to the network. If it is, disconnect it.
2. Resolve the source machine problem that caused the failure.
   
   NOTE: If you must rebuild your hard drive, continue with step 3. If you do not need to rebuild your hard drive, continue with step 7 below.
   
   
3. Install the operating system. Since your source machine is not connected to the network, go ahead and use the source's original name and IP address.
4. Install Double-Take using the same settings you previously used. If you do not recall your previous settings, use the installation defaults.
   
   NOTE: The installation program prompts you to specify if you are using transaction-based applications, such as SQL, Oracle, or Exchange, so that it can establish the appropirate settings for your environment. If you are running transactional applications, select Transactional applications. If you are not running transactional applications, select Non-Transactional applications. If you are unsure whether or not your applications are transaction-based, select Transactional applications.
   
   
5. Install your application software to the same location you recorded previously.
6. On the source server, set the application service, daemon, or NLM to manual startup.
   
   NOTE: If there are multiple services, daemons, or NLMs controlling the application, be sure and set all of them to manual startup.
   
   
7. Verify that the application is not running on the source. The service, daemon, or NLM must not be running at this time. Depending on the type of failure, your service, daemon, or NLM may be set to manual startup but could still be running. Stop the application at this time.
8. Select Start, Programs, Double-Take, Failover Control Center.
9. Select the target machine that is currently standing in for the failed source.
10. Select the failed source and click Fallback.
    
    
    
    The pre-failback script entered during the failover configuration stops the service, daemon, or NLM on the target so that no additional changes can be made.
11. You will be prompted to determine if you want to continue monitoring the source server. Do not choose Continue or Stop at this time.
12. Open the Double-Take Management Console on the source machine (Start, Programs, Double-Take, Management Console), highlight the source machine, and ensure that the replication set is not connected so that replication does not continue after failback is complete. If the replication set is connected, disconnect it by right-clicking it and selecting Disconnect.
13. Connect the source machine to the network.
14. After the source is back online, select whether or not you want to continue monitoring this source machine.
    
    NOTE: The remaining steps can also be run using the Double-Take DTCL automated restoration script, which can be found in Double-Take's User's Guide.
    
    
15. To begin the restoration process, open the Double-Take Management Console and Select Tools, Restoration Manager.
    
    
    
    
16. Complete the appropriate fields as described below.
    Original Source --- The name of the source machine where the data original resided.
    Restore From --- The name of the target machine that contains the replicated data.
    Replication Set --- The name of the replication set to be restored.
    Restore To --- The name of the machine where you the data will be restored. This may or may not be the same as the original source machine.
17. Identify the correct drive mappings for the data and any other restoration options necessary. For detailed information on the restoration options, see Double-Take's User's Guide.
18. Verify that the selections you have made are correct and click Restore. The restoration procedure time will vary depending on the amount of data that you have to restore.
19. After the restoration is complete, start the service, daemon, or NLM on the source machine.
20. Reestablish the Double-Take replication set connection.

At this time, your data is restored back to your source machine, the source machine is again the primary server, and, if you selected to continue failover monitoring, the target is available to stand in for the source in the event of a failure.

More Information