Cloud Computing, the long-held dream of computing as a utility, has the potential to transform a large part of the
IT industry, making software even more attractive as a service and shaping the way IT hardware is designed and
purchased. Developers with innovative ideas for new Internet services no longer require the large capital outlays
in hardware to deploy their service or the human expense to operate it. They need not be concerned about overprovisioning
for a service whose popularity does not meet their predictions, thus wasting costly resources, or underprovisioning
for one that becomes wildly popular, thus missing potential customers and revenue. Moreover, companies
with large batch-oriented tasks can get results as quickly as their programs can scale, since using 1000 servers for one
hour costs no more than using one server for 1000 hours. This elasticity of resources, without paying a premium for
large scale, is unprecedented in the history of IT.
Cloud Computing refers to both the applications delivered as services over the Internet and the hardware and
systems software in the datacenters that provide those services. The services themselves have long been referred to as
Software as a Service (SaaS)
. The datacenter hardware and software is what we will call a Cloud. When a Cloud ismade available in a pay-as-you-go manner to the general public, we call it a
Public Cloud; the service being sold is
Utility Computing
. We use the term Private Cloud to refer to internal datacenters of a business or other organization,not made available to the general public. Thus, Cloud Computing is the sum of SaaS and Utility Computing, but does
not include Private Clouds. People can be users or providers of SaaS, or users or providers of Utility Computing. We
focus on SaaS Providers (Cloud Users) and Cloud Providers, which have received less attention than SaaS Users.
From a hardware point of view, three aspects are new in Cloud Computing.
1.
The illusion of infinite computing resources available on demand, thereby eliminating the need for Cloud Computingusers to plan far ahead for provisioning.
2.
The elimination of an up-front commitment by Cloud users, thereby allowing companies to start small andincrease hardware resources only when there is an increase in their needs.
3.
The ability to pay for use of computing resources on a short-term basis as needed (e.g., processors by the hourand storage by the day) and release them as needed, thereby rewarding conservation by letting machines and
storage go when they are no longer useful.
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