Windows Azure provides a rich platform with adequate built-in features for failover and load balancing.  For instance, when you develop a Web Role, you can deploy multiple load-balanced instances of the Web Role for high availability.  On top of that, you can create policies in Traffic Manager to manage routing of incoming user requests so they will be routed to the Web Role located in the closest data center.  Combining the built-in load-balancing feature with the Traffic Manager policies, you can develop a world-class geographical failover solution very quickly.  Let’s get started on how you can do that.

Prerequisites

1.       Visual Studio 2010

2.       Windows Azure SDK (http://www.windowsazure.com/en-us/develop/net/)

3.       I assumed that you have the ability to create a Web Role cloud application

Deploy Multiple Instances of the Web Role

Once you have the Web Role application, you can change the instance count to 2 or more in ServiceConfiguration.Cloud.cscfg.  The content would be something like this.

<?xml version="1.0" encoding="utf-8"?>

<ServiceConfiguration serviceName="TestSQLAzureOData" xmlns="http://schemas.microsoft.com/ServiceHosting/2008/10/ServiceConfiguration" osFamily="1" osVersion="*">

  <Role name="WCFServiceWebRole1">

    <Instances count="2" />

    <ConfigurationSettings>

...

    </ConfigurationSettings>

    <Certificates>

      <Certificate name="Microsoft.WindowsAzure.Plugins.RemoteAccess.PasswordEncryption" thumbprint="ABEE1F9453061DBAE8B364743736622639D12DCE" thumbprintAlgorithm="sha1" />

    </Certificates>

  </Role>

</ServiceConfiguration>

Next, you can deploy the Web Role via Visual Studio by publishing it to Windows Azure or you can also create a package and deploy it using the Windows Azure Portal (https://windows.azure.com).  To publish to Windows Azure, click “Publish…” in the context menu in Solution Explorer.

If you have not already created a hosted service, you will need to create a hosted service located in a datacenter when you deploy the service.

The next step is to deploy the Web Role to another hosted service located in a different data center like so.

If the deployment is successful, we should now have 4 instances of the Web Role in two geographical datacenters that looks something like this.

Create a Routing Policy

Now, we will create a routing policy using the Windows Azure Traffic Manager.  You will have a choice of Performance, Failover, and Round Robin.  As discussed earlier, the Performance policy routes the users’ requests to the nearest datacenter yielding the best performance from bandwidth perspective and also provide the failover feature in case one datacenter is down.

Once you created the Traffic Manager policy successfully, your solution should now be complete.  The complete policy would look something like this.

Conclusion

Creating a geographical failover solution using the Windows Azure platform can be accomplished with simple steps, but can provide a robust and viable solution that would otherwise be very difficult and expensive to accomplish.