Figure 1. 14 The key types of management and how they are owned for the types of
cloud service
IaaS can be thought of as a virtual machine in the cloud. The provider has a virtual
environment, and you purchase virtual machine instances. You then manage the
operating system, the patching, the data, and the applications within. Examples of
IaaS are Amazon Elastic Compute Cloud (EC 2 ) and Azure IaaS, which give
organizations the ability to run operating systems inside cloud-based virtual
environments.
PaaS provides a framework in which custom applications can be run. Organizations
need to focus only on writing the very best application within the guidelines of the
platform capabilities, and everything else is handled. There are no worries about
patching operating systems, updating frameworks, backing up SQL databases, or
configuring high availability. The organization just writes the application and pays for
the resources used. Azure is a classic example of a PaaS.
SaaS is the ultimate in low maintenance. The complete solution is provided by the
vendor. The organization has nothing to write or maintain, other than configuring
who in the organization should be allowed to use the software. A commercial example
of SaaS is Hotmail, a messaging service on the Internet. An enterprise example is
Office 365 , which provides cloud-hosted Exchange, SharePoint, and Lync services all
accessed over the Internet with no application or operating system management for
the organization.
Ideally, for the lowest management overhead, SaaS should be used, then PaaS if SaaS
is not available, and then IaaS if PaaS is not an option. SaaS is gaining a great deal of
traction with services such as Office 365 , but PaaS adoption is fairly slow. The primary
obstacle for PaaS is that applications have to be written within specific guidelines to
be able to operate in PaaS environments. Many organizations have many custom
applications that cannot be modified or don’t have the budget to change the
application, which is why IaaS is so popular. With IaaS, an existing virtual machine
on-premises can fairly painlessly be moved to the IaaS solution. In the long term, I