When we think of the Windows Azure platform as an “OS of the cloud,” we think of both the services available for applications to use and the type of workloads that can be exercised.
The services that are offered are quite similar to typical operating system services, simply applied at scale to a multi-machine, multi-tenant, and distributed system. This includes:
Deployment services, allowing efficient and rapid allocation of both large and small applications throughout the available and shared resource pool;
Update services, allowing application components and the platform itself to be updated without interruption to the overall execution of the application;
Managed health, allowing automatic recovery from application and hardware failure, without interruption to the overall execution of the application;
Security services, giving certificate management and endpoint control;
Debugging services, allowing remote access to individual machines and remote reimage and reboot capabilities;
Intra-application communication, allowing secure and managed communication across different parts of the application.
In addition to these services offered, we also think about the diverse workloads that can be executed, similar to a general purpose operating system. As you indicate, the Windows Azure platform has capabilities to support web-based applications, notably in the “Web Role,” allowing support comparable to the LAMP stack (with PHP, Java, and .NET support).
However, when you include the capabilities of the “Worker Role” and the “VM Role,” the possible workloads extend beyond just a web-based application. With these additional role types, the workload support includes scale-out high performance computing applications, data processing services, shared file servers, complicated stateful service applications, and all the combinations therein.
Given the services supplied to applications and the diversity of application types that can be executed, we think “Operating System of the Cloud” is a very exciting and very real description for the Windows Azure platform.