We're just past the second anniversary of the launch of Windows Azure. A couple of years' experience with Azure in the industry has provided some obvious success stories, but has deflated some of the initial marketing hyperbole.

As a general principle, Azure seems to work well in providing a Service-Oriented Architecture for services in enterprises that suffer wide fluctuations in demand. Instead of being obliged to provide hardware sufficient for the occasional peaks in demand, one can hire capacity only when it is needed, and the cost of hosting an application is no longer a capital cost. It enables companies to avoid having to scale out hardware for peak periods only to see it underused for the rest of the time. A customer-facing application such as a concert ticketing system, which suffers high demand in short, predictable bursts of activity, is a great example of an application that would work well in Azure.

However, moving existing applications to Azure isn't something to be done on impulse. Unless your application is .NET-based, and consists of 'stateless' components that communicate via queues, you are probably in for a lot of redevelopment work. It makes most sense for IT departments who are already deep in this .NET mindset, and who also want 'grown-up' methods of staging, testing, and deployment. Azure fits well with this culture and offers, as a bonus, good Visual Studio integration.

The most-commonly stated barrier to porting these applications to Azure is the problem of reconciling the use of the cloud with legislation for data privacy and security. Putting databases in the cloud is a sticky issue for many and impossible for some due to compliance and security issues, the need for direct control over data, and so on. In the face of feedback from the early adopters of Azure, Microsoft has broadened the architectural choices to cater for a wide range of requirements. As well as SQL Azure Database (SAD) and Azure storage, the unstructured 'BLOB and Entity-Attribute-Value' NoSQL storage alternative (which equates more closely with folders and files than a database), Windows Azure offers a wide range of storage options including use of services such as oData: developers who are programming for Windows Azure can simply choose the one most appropriate for their needs. Secondly, and crucially, the Windows Azure architecture allows you the freedom to produce hybrid applications, where only those parts that need cloud-based hosting are deployed to Azure, whereas those parts that must unavoidably be hosted in a corporate datacenter can stay there.

By using a hybrid architecture, it will seldom, if ever, be necessary to move an entire application to the cloud, along with personal and financial data. For example that we could port to Azure only put those parts of our ticketing application that capture and process tickets orders. Once an order is captured, the financial side can be processed in our own data center.

In short, Windows Azure seems to be a very effective way of providing services that are subject to wide but predictable fluctuations in demand. Have you come to the same conclusions, or do you think I've got it wrong? If you've had experience with Azure, would you recommend it? It would be great to hear from you.

Cheers,

Tony.