To understand Windows Azure, you must first know a bit about the cloud. Cloud computing (a broader descriptor for the cloud) is all about leveraging the Web as a set of resources for the development and deployment of your solutions. Traditionally, cloud computing has been defined as categories of services — for example, Infrastructure as a Service (IAAS), Platform as a Service (PAAS), and Software as a Service (SAAS). Each one of these categories is fairly different in the context of development. For instance, you might think of IAAS as hosted virtual machines (VMs) you manage remotely; PAAS as where you deploy code, data, binary large objects (BLOBs), web apps, and other application artifacts to a cloud-based environment (such as Windows Server 2008 R2 and IIS); and SAAS as subscription-based services that you can sign up to use (for example, Office 365).
Although these three categories of services dominate the way in which the cloud is characterized, the cloud has four generally accepted pillars:
Figure 5-1 illustrates these four core pillars of the cloud. You can apply each principle in some way to the categories of services.
Both the categories of services and the core pillars of cloud computing apply to Windows Azure. For ...