Cloud Computing and SOA Convergence in Your Enterprise: A Step ...

58 Chapter 3 Defining the Clouds for the Enterprise
Infrastructure-as-a-Service
Infrastructure-as-a-service is really data center-as-a-service, or the ability to
access computing resources remotely. In essence, you lease a physical server
that is yours to do with what you will and that for all practical purposes is
your data center, or at least part of a data center. The difference with this approach
versus more mainstream cloud computing is that instead of using an
interface and a metered service, you get access to the entire machine and the
software on that machine. In short, it is less packaged.
We defined database-as-a-service, storage-as-a-service, and so on, as separate
categories of cloud computing. Infrastructure-as-a-service can provide all
of them, including database, storage, governance, application development,
application processing, security, and more. Anything that can be found in a
traditional data center can be delivered as an infrastructure-as-a-service. The
overlapping feature of infrastructure-as-a-service and the other cloud computing
services can make this a bit confusing.
The advantage of infrastructure-as-a-service is that you can access very
expensive data center resources through a rental arrangement and thus preserve
capital for the business. Moreover, somebody is there to manage the
physical machines for you, including replacement of downed disk drives and
correction of any networking issues.
The disadvantage is that there is typically less granular on-demand expandability
of the resource. With database-as-a-service and storage-as-aservice,
you just purchase additional capability as you need it and as much as
you need. However, many infrastructure-as-a-service providers require that
you lease an entire server for a defined amount of time. Thus, the whole selling
point of adjusting your cloud resources to meet your exact needs kind of
goes out the door.
Next Steps
Keep in mind that the components of cloud computing will change over
time as our thinking and the market evolves. However, the general patterns
presented in this chapter will be relatively consistent as cloud computing
evolves; just the names and the features may change a bit. What is most im-