In the previous article Cloud Equals SaaS, Grid, Utility Computing, Hosting...? I made the following statement:

"SaaS is one of the three possible Cloud Computing delivery modes; however, to be considered Cloud Computing, any of those delivery modes must have certain specific characteristics"

So, in this article we will look at those specific characteristics that define exactly what is Cloud Computing, so that next time you will be able to evaluate if a specific offer is truly Cloud Computing, or simply a pre-existing offering that has the Cloud label slapped on it.

We can state that Cloud Computing allows business to increase IT capacity (or add capabilities) on the fly and in real time (Internet-enabled), without investing in new infrastructure, training new personnel or licensing new software, and as a pay-per-use service.

However, the above definition is not complete. Here is the NIST (National Institute of Standards and Technology) simplified version of Cloud Computing:

The five characteristics:

• On-demand self-service: individuals can set themselves up without needing anyone’s help;
• Ubiquitous network access: available through standard Internet-enabled devices;
• Location independent resource pooling: processing and storage demands are balanced across a common infrastructure with no particular resource assigned to any individual user;
• Rapid elasticity: consumers can increase or decrease capacity at will;
• Pay per use: consumers are charged fees based on their usage of a combination of computing power, bandwidth use and/or storage

The possible delivery models:

• Cloud Software as a Service (SaaS): Customers rent software hosted by the vendor;
• Cloud Platform as a Service (PaaS): Customers rent infrastructure and programming tools hosted by the vendor to create their own applications;
• Cloud Infrastructure as a Service (IaaS): Customers rent processing, storage,networking and other fundamental computing resources for all purposes.

The possible deployment models:

• Private cloud: The cloud infrastructure is owned or leased by a single organization and is operated solely for that organization.
• Community cloud: The cloud infrastructure is shared by several organizations and supports a specific community that has shared concerns (e.g., mission, security requirements, policy, and compliance considerations).
• Public cloud: The cloud infrastructure is owned by an organization selling cloud services to the general public or to a large industry group.
• Hybrid cloud: The cloud infrastructure is a composition of two or more clouds (internal, community, or public) that remain unique entities but are bound together by standardized or proprietary technology).

Here is a chart (created by http://twitter.com/adowbor) that provides a visual summary of NIST working definition of cloud computing:

Note: Private Clouds are also known as Internal Clouds, and Public Clouds as External Clouds.

We can summarize the NIST definition by saying that Cloud Computing is nothing more than a service model where business workloads such as software applications (SaaS), and/or Platforms (PaaS) such as programming tools, and/or Infrastructures (IaaS) such as processing, storage, networking, etc., are used in accordance with the following characteristics:

1. services are provisioned quickly without requiring excessive administrative intervention on the part of the end user’s organization
2. usage of a shared resource model (pool of virtualized resources) to support a cost-effective pricing structure (only pay what you consume), either housed locally within the four walls of the your data center (Private Cloud) or outside the data center at a secondary site or third party hosting facility (Public Cloud)
3. providing self-service interfaces that let customers acquire resources at any time and get rid of them the instant they are no longer needed.

A TRUE CLOUD ABSTRACTS THE UNDERLYING HARDWARE FROM THE BUYER, IS ELASTIC IN SCALING TO DEMAND AND BILLS BUYERS ON A PAY-PER-USE BASIS.

Although the right Cloud Computing definition is important, concentrate on what Cloud Computing does for your business: it provides a way to increase capacity or add capabilities on the fly without investing in new infrastructure, training new personnel, or licensing new software, and you only pay what you “consume”.

In the next articles, I will cover the followings points:
- Why Large Public and Private Sector Organizations (not just SMB's) Are Seriously Considering Cloud Computing?
- What are the Cloud Computing Challenges and Risks?
- Real-World Cloud Computing Applications- Cloud Computing Enterprise Implementation Road-Map

Thanks, and please let me know how can I help you.
Maria Spínola
http://www.twitter.com/MariaSpinola

P.S. Also see:
- Cloud Computing, in Plain English, to IT Directors, VP's, CIO's and CEO's
- Why Should IT Directors, VP's, CIO's and CEO's Care About Cloud Computing?
- Cloud Equals SaaS, Grid, Utility Computing, Hosting...?

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