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How to set up a failover (disaster recovery) between two virtual machines (VMs) by using Double-Take® Availability™?

What is Double-Take® Availability™?

Double-Take® Availability™ for Windows is the first real-time high availability and disaster recovery solution to offer options for physical, virtual, and cloud servers (Vision Solutions® 2015). For example, it provides the ability for a productive server to be either fully migrated to Virtualization Station as a VM or utilize a VM to act as its backup server.   

Please note: Double-Take® Availability™ has different approaches for disaster recovery such as full-server, application-level, and file-level failover. Click here for more information regarding Double-Take® Availability™.

How to set up disaster recovery between two VMs?

Double-Take® Availability™ captures and replicates changes at the byte level from the productive server (Source) to the non-productive backup server (Target) in real-time. These mirroring and replication capabilities allow replicating active files without going offline. If the productive server unexpectedly crashes, the non-productive backup server will take over the existing application services, ensuring data consistency.

  1. Experiment design
  2. Install the Double-Take® Availability™ agent on the source and target system
  3. Manage servers and create a failover job in the Double-Take Console (client)
  4. How Double-Take® Availability™ works for failover
  5. If you want to make the source system run on the original server, VM1, and the target system run in VM2.
  6. Conclusion

 

1. Experiment design

This tutorial demonstrates how Double-Take® Availability™ provides disaster recovery between two VMs from two different QNAP NAS. One VM acts as productive server (Source) and the other is a backup server (Target). Throughout full-server failover, the applications running on the source can be protected against downtime by the backup server taking over.

This tutorial uses the “Source System” to represent the productive server and the “Target System” is the backup server.

Requirements:

  • Two network adapters of a VM: the first is for applications running on the VM, and the second for data synchronization between the source and target.
  • Prepare the same Windows Server version for the target system. Please note that you do not have to install the same applications in the target system that the source system has. All the applications will be prepared for the target system during failover.
  • Double-Take® Availability™ licenses (please consult your local distributors to obtain licensing information).
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1.1 VM1: Source_System

As Double-Take® Availability™ needs two networks for application services and data-synchronization, two virtual switches are required in Virtualization Station. Add two network adapters on the source system and connect to the virtual switches.

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In Virtualization Station's Network Setting, ensure the network adapters are connected to the virtual switches (Application service: 172.17.22.xxx/ Data-synchronization: 192.168.0.xxx).

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For better recognition, we will refer to VM1 as “Source_System”.

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1.2 VM2: Target_System

Same network settings as VM1.

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For better recognition, we will refer to VM2 as “Target_System”.

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1.3 Double-Take Console (Client)

This tutorial uses a Windows 7 (VM) installed with the client components of Double-Take® Availability™ to manage high availability and disaster recovery. You can add servers as sources or targets and create failover jobs in the Double-Take® Console.

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2. Install the Double-Take® Availability™ agent in the source and target system

For full-server failover, the source and target system should have the Double-Take® agent installed. If a disaster occurs, it will be detected and Double-Take carry out the failover.

  1. Execute the Double-Take installation and click “Unzip”.
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  2. After the file has been unzipped, click “Install Double-Take Availability”. Select a language for the installation and then click “OK”.
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  3. Click “Install”
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  4. Choose “No, skip this step and continue the current installation” and click “Next”.
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  5. Read and accept the license agreement and click “Next”.
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  6. Click “Next’.
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  7. Choose “Server Components Only” and click “Next”.
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  8. Double-Take will use port 6320, 6325 and 6326 to communicate with the source, target and the client side. Choose “Open only the ports that are not in use.” and click “Next”.
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  9. Enter the license key and click “Next”.
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  10. Choose “Limit disk space for queue (MB)” and specify 2048 MB capacity. Click “Next”.
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  11. Click “Next”.
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  12. Click “Install”.
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  13. Click “Finish”.
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3. Manage servers and create a failover job in the Double-Take Console (client)

Please follow the section 2 instructions to install the Double-Take Console in the client (Windows 7). Please note that you need to select “Client Components Only” in step 7. After the client has been installed, you can manage servers and create failover jobs in the Double-Take® Console.

  1. Start the Double-Take® Console.
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  2. Click “Get Started” in the Double-Take® Console.
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  3. Click “Add servers”.
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  4. In this tutorial, the source system uses IP 192.168.0.111, and the target system uses IP 192.168.0.222. Enter the “User name” and “Password”.
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  5. After adding the source and target, click “OK” to add the servers.
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  6. The source system and target system will be added.
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  7. To create a failover job for disaster recovery, click “Get Started” and choose “Double-Take Availability”. Click “Next”.
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  8. Choose “Protect files and folders, an application, or an entire Windows or Linux server” and click “Next”.
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  9. Choose “Source_System” as a source server and click “Next”.
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  10. Choose “Full Server” and the system drive will be selected as default. Click “Next”.
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  11. Choose “Target_System” as target server and click “Next”.
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  12. There are some options for configuring failover.
    • General
      Enter a job name.
    • Failover Monitor
      Set the period of time in which no response from the source system will trigger failover. Check the “Network monitoring” and select the source IP address.
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    • Failover Options
      To manually initiate failover, check “Wait for user to initiate failover”. On the other hand, the failover will be triggered automatically with uncheck.
    • Failover Identity
      To apply the source network settings, check “Apply source network configuration to the target (Recommended for LAN configurations)”. For instance, the source system IP 172.17.22.187 will be kept and used by the target server after failover.
    • Reverse Protection
      If you want to reverse the target system to the original server, check “Enable reverse protection”. To enable reverse protection, you need to choose an existing IP address to identify the source and target system. For instance, IP 192.168.0.111 is used for the source system, and IP 192.168.0.222 is for the target system.
      More information about Reverse Protection.
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    • Network Adapter Options
      Please ensure the corresponding network settings between the source and target system. For example, the network adapter of the source system [172.17.22.187] should be associated with the target’s adapter [172.17.22.173].
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    • (Optional) Mirror, Verify & Orphaned Files/ Staging Folder Options/ Target Services/ Snapshots/ Compression/ Bandwidth/ Scripts
      These options are good enough for a failover job. For these listed options, you can configure them for certain usages. Afterwards, click “Next”.
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  13. Double-Take® will check all configurations. Click “Finish”.
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  14. After creating a failover job, all of the files and applications on the source system will be mirrored on the target system.
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  15. When the data synchronization has been finished, all of the changes on the source system will be automatically replicated to the target system and the target system will be standby for failover.
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4. How Double-Take® Availability™ works when a disaster occurs

This tutorial demonstrates how the target system (VM2) will take over the source system (VM1).

  1. In the VM1 information page, click “Power”, choose “Force Shutdown” and click “Apply”. The source system will be immediately shut down.
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  2. Go to the Double-Take® Console. The failover condition will be met and the “Failover” button turns into enabled.
    (Please note: if you choose “Wait for user to initiate failover” in the Failover Options, this icon will be enabled until you click it. If not, the failover will be automatically triggered.)
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  3. Click “Failover”.
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  4. After processing the failover, the target system will be restarted and will take over all of the application services that the source system has.
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    In VM2 (formerly the target system), the computer name will change to “Source_System” and the IP address will apply the original source system 172.17.22.187. However, IP 192.168.0.222 is still kept in VM2. This IP address is used to identify the original system if reverse protection is activated.
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  5. If the source system (VM1) returns, you can use reverse protection to restore the original target system to VM1. Go to the VM1 information page and click “Start” to invoke VM1.
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    After starting VM1, both VM1 and VM2 will run the same source system.
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  6. Click “Reverse” and “Yes”.
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  7. After clicking reverse, Double-Take® will restore the original target system to VM1.
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    VM1 will run with the target system and use the original network setting (172.17.22.173).
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  8. Afterwards, Double-Take® will carry out synchronization again.
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    After the data is synchronized, the failover job will be changed from VM2 to VM1 (VM2 is running the source system, while VM1 is the target system and acts as the backup server.)
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5. If you want to make the source system run on the original server (VM1) and the target system run on VM2.

It will need to failover and reverse again.

  1. Click “Failover” and “Failover”.
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  2. When the failover finishes, VM2 will be shutdown and VM1 will be restarted. All the data will be replicated and the application services will be taken over from VM2 to VM1.
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    VM2 will power-off and the failover job will display a warning.
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  3. Go to the VM2 information page and click “Start”.
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    Both VM1 and VM2 are running the same source system.
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  4. Go back to the Double-Take® console. Click “Reverse” and “Yes”.
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  5. After clicking the reverse button, Double-Take® will restore the original target system to VM2.
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  6. VM1 is running the original source system, and VM2 has been reverted to the target system as the backup server.
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  7. Afterwards, Double-Take® will synchronize again.
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    The original failover job will be ready again.
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6. Conclusion

Double-Take® Availability™ provides a high availability and disaster recovery solution for your productive server. Furthermore, it allows you to adjust the failover configuration to obtain a faster, reliable full server failover with flexible RTO and RPO.

 

Reference

Vision Solutions. (2015). Double-Take Availability. Available: http://www.Vision Solutions.com/products/windows/double-take-availability/overview. Last accessed 4th Nov 2015.

Datum vydání: 2016-02-03
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