Database Reference
In-Depth Information
Network-based provisioning : the cloud is usually accessed via (hopefully) secure channels
through the public Internet. Actually the cloud in many cases really is just another company's
data center.
Multi Tenancy : Due to the nature of cloud systems it is likely that you are sharing an
environment with someone else in a certain way. Although environments are isolated from
one another, workload peaks may still filter through.
Self-management : The cloud infrastructure provided should allow users to tweak their
configuration. Public clouds especially allow the user to choose from a variety of virtual
machines, ranging from very small to really, really big. Additionally many cloud providers
expose management options such as starting, stopping, and cloning cloud systems to
customers.
Cloud computing, making use of consolidated environments with a high degree of automation, could well be the
future for the majority of computing needs. Let's continue by discussing each layer in more detail.
Infrastructure as a Service
My first contact with the cloud was by using Infrastructure as a Service (IaaS). Since then I have used IaaS in a number
of projects. Opting for IaaS as opposed to other cloud deployment options gives the user the greatest flexibility, but
also most responsibility for the environment. The option to install software on the system and to have full control over
it gives the user said flexibility but it comes at a price. At the same time the system administrator is responsible for its
security and for keeping it current in terms of patching.
The value proposition by the industry heavyweights (Amazon AWS maybe the best known) shows that the
upfront investment in hardware can be costly. The initial deployment could also be undersized and unable to deal
with unexpected peaks in the workload. Infrastructure as a service allows the user to add capacity on demand
within very little time. In an IaaS environment the user gets a virtualized environment, often termed an instance.
The user has full control, is able to install software, and modify the storage layout and any other parameter in the
environment. Cost for operating such an instance is most often calculated depending on the type of the instance
and its characteristics such as memory capacity, isolation from other users, and CPU power. Similar in a way to the
popular root server which offers even more flexibility in regards of the software installation, a virtual instance needs to
be maintained and hardened by its user to prevent security breaches.
Software as a Service
Software as a service (SaaS) is the most common touch-point to the cloud for non-infrastructure providers or
developers. The model behind Software as a Service goes back a while, and in its basic form presents an application
via the Internet. The application can be simpler (it wouldn't really be simple) such as a web mail interface, or rather
complex such as Sales Force.
SaaS as a concept probably does not need much introduction as it has been around for so long and many of us
have already used it in some form. The first web clients appeared in the early half of the last decade, and since then
there has been a consolidation of providers. Some of them, like Google, have successively enhanced their offering
from the original core capability to web-based office suites. Established “fat client” vendors also offer an increasing
number of web-based services to supplement their established revenue streams. A little while ago a hardware device
was released by Google which is based entirely on the services provided over the Internet. Although such a class of
devices is appealing in certain situations, the biggest drawback to them is their limited functionality when in offline
mode. Who knows, we might see more of these in the future when true mobile broadband becomes a reality at a
reasonable cost.
 
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