Cloud computing models: Which one is best for your business?

With so many different cloud computing models and cloud definitions, how do you know which one is best for your business? Industry experts explain each aspect of the cloud.

Now that cloud computing seems to be more than just another buzzword, it's important to find out which cloud service is right for your business. But with so many cloud computing models to choose from, and so many different definitions, where do you start?

Which cloud computing model for which size business?
Christoph Reichert, VP of HPC sales EMEA at Platform Computing, said large organisations can outsource their underutilised computing power to others for free.

"Doing this means smaller enterprises can tap into computing power that was previously beyond their means and blur the boundaries between the traditional concepts of business. Start-ups, for example, will be able to use applications that require high-end computing resources. Harnessing the power of a computer network rather than a couple of servers, these smaller companies will be in a position to compete with organisations many times their own size," he said.

Nigel Tozer, business development director ,EMEA, at CommVault, said trying to put types of cloud offering into different corporate "bags" is quite tricky because of the myriad of applications and services available.

A cookie-cutter approach will not result in an effective use of the cloud.


Dr Chris Harding, Director of the SOA Work Group at The Open Group,

Tozer added: "I think one differentiator is the total percentage of IT services that organisations source via the cloud. Big corporate entities may use just one application and manage everything else themselves, whereas midsize and smaller businesses may use more services to keep their own IT costs down but still have the sophistication to compete with the big boys."

Dr. Chris Harding, director of the SOA work group at The Open Group, feels there is no "right" cloud for a particular type of business.

"You need to understand the advantages and disadvantages, both from a business and from a technical perspective, of each of the different kinds of cloud service. Then you can determine how they should integrate with, or replace, the services already provided by your in-house IT department. A cookie-cutter approach will not result in an effective use of the cloud," said Harding.

When considering cloud computing services, there are two important dynamics to consider. First, what is the right resource model for the cloud-based application? Second, what is the right tenancy model for the business?


Choosing the right resource models
Owen Garrett, cloud computing expert at Zeus Technology, said which model to use depends on the services and how effectively they can be provided by a cloud provider.

Infrastructure as a Service (IaaS)
This is the most fundamental type of cloud computing, according to Garrett; outsourcing hardware virtualisation.

"If a variety of complex, custom applications are run in-house, these may lend themselves to an IaaS cloud service. This type of service avoids the cost of investing in the hardware that these applications run on, replacing this with a pay-by-use model where the resources required are rented with no up-front expense or residual cost if they stop being used," said Garrett.

Garrett gave the example of how a retail site may operate a number of Web servers, inventory databases, CRM and other applications. They may need to hold spare resources in reserve to cope with seasonal shopping spikes in Web traffic.

"This resource is an expensive waste when it is not used. Using a cloud IaaS service, such as Amazon EC2, would eliminate the cost of operating the hardware," he added.

However, Garrett pointed out that this type of cloud can cause concerns over data security. For example, cardholder data must be managed within the terms of the PCI DSS specification which precludes the use of many IaaS clouds.

David Shacochis, vice president of product research and development for Savvis, said IaaS clouds offer core IT services such as network, compute, security, operating systems, middleware engines, load balancers and storage. Customers can build application architectures in an IaaS cloud.

Platform as a Service (PaaS)
Garrett explained that PaaS is deploying applications on an external cluster of application servers rather than ones you operate in-house.

"If you build applications that are targeted to a particular platform, such as .NET, LAMP or Java, a cloud PaaS provider that hosts an instance of that platform may be preferable. PaaS platforms are a lot less commonplace because providers often cannot give customers the control and diversity that they require for their applications.

Furthermore, vendor lock-in is another concern; as soon as the application begins to use any proprietary tools or interfaces that a PaaS provider makes available, migrating to another provider suddenly becomes very difficult, Garrett said.

For this reason, he added, PaaS platforms are typically used for new, greenfield projects where the organisation has confidence in the longevity of their selected PaaS provider and they are prepared to target their application development specifically for that platform.

According to Shacochis, PaaS clouds offer run-time environments whereby uploaded code can be interpreted, operated and scaled.

He added: "Different PaaS platforms can be oriented toward specific software languages, or they can be focused on higher-level abstractions such as workflows or business processes. Customers run application code in a PaaS cloud."

Software as a Service (SaaS)
According to Garrett at Zeus Technology SaaS is replacing in-house applications with an external application accessed via the Web and is often the most straightforward choice.

"The key differences are in the costs of using the application, and the mode of use. SaaS applications are typically accessed remotely using a Web browser, so they are more accessible but may not perform as well as local applications for certain tasks," he added.

"The entire infrastructure and coding platform is completely abstracted, allowing for efficient software updates and continuous improvement to the user interface. Customers create user accounts in a SaaS cloud," Shacochis added.

The five primacy tenancy models of cloud computing
According to most industry observers, there are five primary tenancy models emerging within the enterprise, depending on how each company wants to structure its procurement and cost modelling.

Private cloud
Simon Gay, European head of data centre and storage solutions at systems integrator Dimension Data, said: "Private cloud is often chosen by companies handling sensitive data or retailers who need to comply with PCI DSS or similar regulations. In short, it can offer some cost savings but provides a higher level of security."

Savvis' Shacochis said many IT professionals consider the emergence of private cloud architectures as simply the natural evolution of virtualisation and automation technologies. He said: "In the private cloud model, IT spends capital on hardware and software and uses management tools to determine appropriate chargeback to its business constituents. Whatever capital is left over, of course, is borne by the IT department."

Mark Oldroyd, senior technology sales specialist at Novell, said the private cloud is usually built for single organisations that typically use it to virtualise operating systems and networks and consequently reduce the number needed.

Public cloud
Dimension Data's Gay said most people are familiar with the public cloud.

"The public cloud involves using shared infrastructure -- something many people like in terms of cost but not with regards to security. Consequently companies need to think about what is hosted in the public cloud," he said.

Shacochis said this model enables the service provider to instantiate cloud resources on-demand in a purely pay-as-you-go service model.

He said: "Server providers that offer public clouds are able to offer usage-based billing and zero commitments because the underpinning IT infrastructure is part of a common resource pool that can be redeployed to other customers."

Novell's Oldroyd said this cloud is generally available across the Internet and serves a virtually unlimited number of customers with the same infrastructure. Popular public cloud offerings include Amazon, Rackspace,, Microsoft and Google.

Hosted cloud
Shacochis explained the hosted private cloud is a model whereby a service provider is able to offer up a private cloud architecture in a remote data centre that is completely dedicated to the customer. The enterprise benefits from not having to spend time designing the architecture or writing automation software, and they are able to convert all expenditures from up-front capital to consistent operational expense, according to Shacochis.

Hybrid cloud
Shacochis said a hybrid cloud allows enterprises to adopt a mixture of these tenancy models to achieve a flexible data centre strategy.

Oldroyd at Novell said this model allows data to flow between clouds or private cloud applications to temporarily access public cloud resources for extra capacity during busy periods.

Community cloud
Oldroyd explained the community cloud is built for a discrete and well defined number of businesses and works well for supply chains or collaborating government agencies.

Kayleigh Bateman, is the Site Editor for

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