IaaS, PaaS and SaaS—All Cloud, All different

As mentioned in the preceding section, the importance of applications in a virtualized environment has brought about three major trends in cloud computing:

• Infrastructure as a Service (IaaS): Used to manage low-level resources like VMs and disks. The end user is responsible for what is running within the VM, starting with the OS. IaaS is most closely related to a regular automated virtualized system. Amazon Web Services is maybe the best-known provider for an IaaS-style cloud service, but there are numerous others in the market.
• Platform as a Service (PaaS): Provides faster development and deployment platforms by abstracting the user from the OS while adding well-defined APIs to many essential services (such as the Web, databases, mail, queues, and storage) that the developer must use. Both sides benefit; development should be faster and the end product should be more reliable more quickly. Typically PaaS also provides monitoring and administrative consoles tightly designed around the platform, making operations easier. At the same time, by maintaining tight control over what is executed when, PaaS can make better decisions about machine load, at least in theory. Another side effect is a vendor lock-in, desirable to the vendor but maybe not to the developer. Windows Azure is a good example of a PaaS-style cloud.
• Software as a Service (SaaS): Instead of writing and maintaining every application, one uses online services. Examples include Google Mail and Salesforce. It is important to note that the SaaS software provided by a vendor might not be running in a cloud, but SaaS offerings often make sense when developing an application for the cloud. For instance, if I develop an e-commerce solution in the cloud, I might not want to reinvent my own load balancers, databases, or payment-processing system. I might not even want to run or operate them; perhaps all I want is to use these services. Using SaaS vendors allows me to concentrate on my own application.

Virtualization, as well as the three cloud platforms discussed, have a major impact on the discipline of application performance monitoring (APM).

Cloud computing-performance management is not only a big technical challenge, but in my mind, a real game changer, as well. By making infrastructure a throwaway commodity, focus is shifted to the application by default. At the same time, you are losing a little bit of control and, in the case of a public cloud, visibility, making your application and operation more dependent on third parties.

PaaS and SaaS go one step further and outsource parts of the application itself, putting ever more focus on our core business and core application while depending even more on third-party black-box services. Therefore, APM comes into its own in the cloud. In the next section we'll look at the implications of virtualization on performance management.