Private vs. Public Cloud: What Is Good For Your Business?

Over the last 18 months the debate as to which type of cloud - private or public - is better has been hotting up. As far as Tom Brand, virtualisation practice lead at Glasshouse Technologies (UK) is concerned there is no debate: neither is better. He explains below:

Don’t get me wrong, I’m not saying cloud computing isn’t a viable option, just that organisations need to look at a number of factors before making any strategic cloud decisions:

How large is the organisation?

What are my cloud computing requirements?

What constraints do we have?

How much will it cost to transition to the cloud?

The size of an organisation has a significant impact on the type of cloud model they are likely to use. SMBs tend to have limited capital expenditure and basic IT requirements, in particular security, making them perfect candidates for end-to-end solutions from a public cloud infrastructure.

With the rapid growth of Software-as-a-Service (SaaS) and Storage-as-a-Service, many organisations no longer have to manage any kind of IT infrastructure at all.

Businesses can simply take advantage of day-to-day applications being delivered via the Internet on a pay-as-you-go model (Google Apps is perhaps the most dominant offering on the market).

In particular start-ups with little capital expenditure and few resources are very unlikely to invest in new equipment, turning to the public cloud instead to provide a cost effective alternative.

Larger organisations will have to approach public cloud offerings with a different strategy. It is unlikely that a large enterprise will move its entire infrastructure to the public cloud for a number of reasons, including but not limited to; security; legacy apps; performance; existing assets and so on.

Instead, enterprises are more likely to run some form of private cloud or a combination of private and public cloud solutions. By reviewing the existing infrastructure and future requirements from a business, technical and operational perspective, an organisation will be able to make decisions regarding their cloud strategy at a more granular level, including the cost to transition or transform.

It’s safe to say that over the next few years enterprises will start to seriously consider deploying new applications out to the public cloud and where possible, resorting to internal, bespoke solutions as a last resort.

Some of the key features of cloud computing is the ability to provide lower cost, pay-as-you-use, flexible computing. To achieve this requires two key components – economies of scale and automation. Only large enterprises and service providers really have the scale, budgets and resources to provide these and this is why the private cloud has a limited market.

There was much discussion recently about the practicalities of implementing cloud at the Forth International Cloud Computing Conference & Expo ( in the US.

While some organisations described how they have built a flexible, secure and cost effective private cloud, others were less convinced, citing high development costs, warning businesses not to underestimate the level of effort and time required to create a private cloud infrastructure.

Typically, only if an organisation has strict in-house policies, often based on security requirements, is a private cloud worth embarking on. Banks and government bodies are good examples of this where they have infrastructures sizable enough to create economies of scale, but the data must not be kept on a shared infrastructure.

One compromise to the problem is the ‘Virtual Private Cloud’ where service providers host dedicated clouds for customers. Customers take advantage of the tools and expertise of the service provider that manages the cloud, however the underlying infrastructure is dedicated to that customer.

Using this model, particularly for Infrastructure-as-a-Service (IaaS), enterprises get the low cost, pay-as-you-use flexible computing without the security, compliance and performance concerns of the public cloud, or the investment required to develop their own cloud infrastructure.

However you look at it, the cloud is a service orientated architecture and this means it is based on SLAs. Perhaps the biggest concern we see with the enterprise cloud is the SLAs service providers are committing to, especially in the ‘one size fits all’ world that is the public cloud.

Most of the SLAs are availability based with little consideration to performance and recovery, both key requirements of an enterprise class IT infrastructure. As the public cloud grows and becomes more and more federated, with cloud providers offering services based on other cloud solutions, SLA could be hard to track and manage.

In summary, there is no right or wrong answer. The cloud offers a vast number of solutions across a wide range of deployment models but organisations need to carefully review their requirements and the services offered by providers before flying into the clouds.....