think PaaS will become the standard for custom applications, but it will take a long
time, and I think IaaS can help serve as the ramp to adopting PaaS.
Consider a multitiered service that has a web tier, an application tier, and a SQL
database tier. Initially, all of these tiers would run as IaaS virtual machines. The
organization may then be able to convert the web tier from IIS (Internet Information
Services) running in an IaaS VM and use the Azure web role, which is part of PaaS.
Next the organization may be able to move from SQL running in an IaaS VM to using
SQL Azure. Finally, the organization could rewrite the application tier to directly
leverage Azure PaaS. It’s a gradual process, but the reduced overhead and increased
functionality and resiliency at the end state is worth it.
As will be explored in this book, a key Microsoft differentiator is its hybrid capability
to enable organizations to have a complete choice when deploying services, without
having to change how they architect and create applications. When using Microsoft
Azure Stack on-premises, an organization can write an application on the Azure
Resource Manager (ARM) model and deploy it on-premises, to the public cloud, or to
a hosting partner that leverages Microsoft Azure Stack. If a JSON (Java Script Object
Notation) template is created to deploy a service to ARM, it can be deployed on-
premises, to a hosting partner, or to Azure without modification. Typically,
organizations will not pick one, but will utilize all of the options in the scenario where
a particular type of hosting makes the most sense.