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The key concepts of cloud computing

Turning down the noise so you can assess the real promise

By Marcela Cueli, product marketing manager, Data Center, Security & Outsourcing, Global Crossing, special to Network World
July 01, 2010 05:03 PM ET
This vendor-written tech primer has been edited by Network World to eliminate product promotion, but readers should note it will likely favor the submitter's approach.

Network World -  we are bombarded daily with ads about products, white papers, publications, seminars, workshops, market projections and more focused on cloud computing. But if you analyze these messages you reach the conclusion there are many ambiguities and only a few emerging concrete terms.

For a start, cloud computing is not a technology but a model of provision and marketing IT services that meet certain characteristics. Cloud is all about computer services, not products:

* The infrastructure is shared. Multiple clients share a common technology platform and even a single application instance.

* The services are accessed on demand in units that vary by service. Units can be, for example, user, capacity, transaction or any combination thereof.

* Services are scalable. From the user's point of view, services are flexible; there are no limits to growth.

* The pricing model is by consumption. Instead of paying the fixed costs of a service sized to handle peak usage, you pay a variable cost per unit consumption (users, transactions, capacity, etc.) that is measured in time periods that can vary, such as  hour or month.

* Services can be accessed from anywhere in the world by multiple devices. The cloud model leads to basically two different kinds of clouds: private and public. The public clouds are those that offer IT services to any customer over the Internet. Private clouds offer IT services to a predefined group of customers, with access through Internet or private networks. You might have also heard about internal and external clouds. The former are a subgroup of the private clouds, and provide services within the same company or corporate group. The latter may be public or private and provide services to other companies.

FAQ: Cloud computing, demystified

IT services provided through the cloud are grouped into three categories: infrastructure-as-a-service (IaaS), platform-as-a-service (PaaS) and software-as-a-service (SaaS).

IaaS provides the processing environment (servers, storage, load balancers, firewalls). These services can be implemented through different technologies, virtualization being the most common one, but there are implementations that use grid technologies or clusters.

PaaS provides an environment for developing and running applications. Authentication, authorization, session management and metadata are also part of this service.

SaaS is the most advanced and complex cloud model. The software services provide functionalities that solve user problems, whether it's an individual or an employee of a company. Some examples of solutions that are now offered under the SaaS model include: business intelligence, Web conference, e-mail, office automation suites and sales force automation.

The benefits of this model are clear and very attractive: to access a comprehensive service, eliminate investments, defer some costs and eliminate others, increase agility of IT areas, increase user mobility and improve the availability of services.

However, given the novelty of the model, there are some aspects that have not yet been resolved, and as in all work environments, there are risks that must be taken into account when assessing how, when and for what to use this new tool that is available to IT areas of companies.

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