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Historical Perspective
Cloud computing is realized through the advent of the Internet. As such, the concept of
the cloud is relatively new. The general idea according to Biswas (2011) can be traced to the
1960’s when John McCarthy noted, “computation may someday be organized as a public
utility.” McCarthy’s premonition foresaw the advent of grid computing in the early 1990’s,
analogous to connecting the nation through an electric power grid. With advances in technology
– speed, capability, and reduced cost – the ability to distribute computational power has become
reality.
One of the first companies to embrace the cloud was Salesforce.com, which developed an
application for delivering sales and customer relationship management (CRM) services via the
Internet (Biswas, 2011). Others followed suite with Amazon Web Service (2002), Google Docs
(2006), and Amazon’s Elastic Compute Cloud (EC2). In 2007 Google and IBM partnered with
higher education to introduce cloud computing to academia (Lombardi, 2007). Finally,
Microsoft entered the arena with the introduction of Windows Azure in November 2009.
Adaptation to the cloud will continue to evolve and grow in 2011 and beyond as
businesses and academic institutions look to leverage their IT dollars and do more with less.
One only has to look at the aforementioned initiatives by Amazon, Google, and Microsoft to
realize the advent of cloud computing is here.
Cloud Computing Models
Cloud computing, as noted by Hurwitz, Bloor, Kaufman and Halper (2011), is comprised
of the set of hardware, networks, storage, services, and interfaces whose combination deliver
computing as a service. The “cloud” is typically delivered in three different configurations to
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meet the needs of the particular organization. These include Infrastructure as a Service (IaaS),
Platform as a Service (PaaS), and Software as a Service (SaaS) as outline in Table 1.
Cloud Model
Definition
Infrastructure as a Service (IaaS)
Platform as a Service (PaaS)
Software as a Service (SaaS)
The storage and computational resources
necessary to run a cloud, providing access over
the Internet. Sometimes referred to as
Hardware as a Service (HaaS)
The platform utilized with the cloud,
controlling allocation of servers, bandwidth
and storage
Providing software applications through the
Internet without the need host or manage the
applications on one’s own computer
Table 1 – Cloud Models
Classifications
In addition to the aforementioned cloud models, clouds are classified as public, private,
or hybrid clouds. Public clouds are the equivalent of data centers outside of an entity’s firewall
providing resources on demand via the Internet. Examples include Amazon Elastic Compute
Cloud (EC2), IBM's Blue Cloud, Sun Cloud, Google AppEngine and Windows Azure Services
Platform (Public Cloud, 2011). In contrast, private clouds such as Citrix1 and VMWare2 are
inside an organization’s firewall or private space within a cloud service provider’s data center.
Finally, hybrid clouds contain aspects of both private and public clouds. Figures 1 and 2
highlight the basic characteristics of these cloud types.
Citrix is a terminal server system that allows users access over the Internet to software
applications from remote locations.
1
VMware provides virtualization of servers – providing multiple virtual instances of an
operating system on one machine, reducing the number of physical machines – as well as cloud
infrastructure.
2
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Figure 1 – Public and Private Cloud Examples3
Figure 2 – Hybrid Cloud Example3
3
From the Cloud Storage Strategy website at http://cloudstoragestrategy.com/2010/01/cloudstorage-for-the-enterprise---part-2-the-hybrid-cloud.html
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Characteristics
According to Amrhein (2009) there are several key characteristics essential for effective
and efficient use of cloud services, regardless of which model or classification is utilized. These
include a shared virtualized infrastructure, self-service access, elastic resources, consumable
output, and usage tracking shown in Table 2.
Shared, virtualized infrastructure: At the heart of cloud computing is one of its
key technological enablers, virtualization. Virtualization provides a path to share
pools of IT resources such as servers, storage, data, and more. Virtualizing and
sharing resources can realize higher utilization rates. Effectively, more can be done
with less, or more can be done with existing resources.
Self-service access: Cloud computing solutions should enable self-service
capabilities to their users. Some type of portal, usually web-based, replaces the
days of human-driven resource provisioning requests, allowing authorized users to
directly access compute resources based on their need.
Elastic resource pools: Whether cloud computing concepts are being applied to a
set of servers, blocks of storage, or shards of data, the resource pool should be
elastic. This means that as more resource is needed, the system provisions more
from the pool to ensure demand is met. Conversely, and just as importantly, when
a resource is no longer needed it should be returned to the pool. This dynamic
growth and contraction should be carried out autonomically based on parameters
defined by users of the cloud.
Consumable output: Once resources are provisioned within the cloud, they should
be as close to “ready-to-go” as possible. Configuration, tuning, and integration
should be handled by the cloud computing solution where possible allowing users
to derive immediate value from the provisioned components.
User-based usage tracking: This feature is really a need created by the first
characteristic mentioned. If the cloud is offering up shared resource pools, it is
necessary to understand who is using those resources and how much they are
using. Cloud computing solutions should provide a way to allocate usage of its
resources to a particular user or group of users in order to facilitate chargeback
within a business
Table 2 – Cloud Characteristics
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References
Amrhein, D. (2009). Forget Defining Cloud Computing. In the IBM Ulitzer website. Retrieved
from http://ibm.ulitzer.com/node/1018801
Biswas, B. (2011). A History of Cloud Computing. In the CloudTweaks website. Retrieved from
http://www.cloudtweaks.com/2011/02/a-history-of-cloud-computing/
Hurwitz, J., Bloor, R., Kaufman, M., & Halper, F. (2011). What is Cloud Computing? In the
Dummies.com website. Retrieved from http://www.dummies.com/how-to/content/what-iscloud-computing.html
Lombardi, C. (2007). IBM and Google team up on cluster computing. Retrieved from
http://www.zdnet.co.uk/news/it-strategy/2007/10/08/ibm-and-google-team-up-on-clustercomputing-39289873/
Sultan, N. (2010). Cloud computing for education: A new dawn? International Journal of
Information Management, 30(2), 109-116.
Public Cloud: a definition. (2011). In the SearchCloudComputing.com website. Retrieved from
http://searchcloudcomputing.techtarget.com/definition/public-cloud