Public Cloud vs Private Cloud vs Hybrid Cloud


This is George Favaloro holding up his ‘cloud’ business plan from 1996 with Compaq Computing.

Cloud computing is not a new technology. Despite the term ‘cloud’ being made famous by’s outstanding guerrilla marketing activities in the early 2000’s. The concept of cloud has been around a lot longer than

For example an ERP provider I used to work for called ECi Software Solutions unknowingly created their own cloud solution by accident. One of their sales people was getting tired of having to cart around all of the hardware to meetings to be able to demonstrate their ERP platform.  So she set her demo server up in her office and connected to it via Terminal Servers (where you log into one computer from another computer) from her customers’ offices.

Whilst Marc Benioff the founder and CEO of gets a lot of the credit for creating the cloud, the true creators of cloud and the first people to coin the phrase were 2 guys called George Favaloro and Sean O’Sullivan who had formed a company called Compaq Computing (later known as Compaq). They went on to create a $2billion business selling servers to internet companies.

Almost 20 years on and cloud has become a buzzword that relates to most technology in our lives, whether it is the sat nav in our cars, Spotify on our iPhones or the business systems we rely on to run our businesses cloud is everywhere.

Today there are new cloud buzzwords:  ‘private’, ‘public’ and ‘hybrid’. The good news is that unlike most buzzwords they are accurate names.

In this article I wanted to take a look at these different types of environment in a little more detail and look at some of the pro’s and con’s of each environment.

Multi-Tenancy or Single-Tenancy?

In the case of an externally hosted cloud the customer is defined as a ‘tenant’. I like this term as for non technically minded people like myself I can relate it to tenants who rent property – For example the term ‘multi-tenancy’ is used to describe a public cloud environment where multiple instances of applications are run within one environment, in the property rental analogy the tenant is a somebody living within a block of flats. They all share the same infrastructure, but, live in individual homes. By comparison single-tenancy is where the tenant is living within a detached home and is not sharing their infrastructure  with any other tenants. Multi Tenancy vs Single Tenancy Cloud Hosting

Public Cloud

Public CloudA Public cloud is generally provided “as-a-service” over the internet and the organisations application are hosted at the vendors premises. Generally the organisation has little control over environment in which the application is hosted and the core infrastructure is shared between many organisations.

Each organisations data and application is logically segregated so that only those authorised are allowed access.

Security is ALWAYS at the forefront of decision makers thoughts when they are considering the cloud and rightly so. The level of security is entirely relative to the vendor hosting the public cloud. Think about it like this – Enterprise hosting centres are usually either purpose built buildings or buildings that were previously used as vaults by businesses like banks. Their soul purpose is to keep your data safe and accessible to you. By comparison on-premises installations stored within organisations premises are often by no means as secure, yet they don’t suffer the same security concerns.

The advantages of a Public Cloud are:

Low Cost - The nature of the public cloud is that you only pay for what you use. So as an organisation grows or shrinks so do the associated costs. By comparison a private cloud may require a commitment that see’s the infrastructure designed to cope with growth and thus is more expensive, likewise costs aren’t saved if the organisation shrinks. The other big cost saving is within an organisations I.T. department. Costs relating to infrastructure relating to the hardware and running costs will be reduced greatly as will the associated costs of the I.T. team running them.

Increased Efficiency - As public clouds will have dedicated teams working on maintaining the infrastructure downtime is less likely to be an issue. On top of this if your applications are hosted by your software provider updates are usually managed by the software vendor, so expensive upgrades are  a thing of the past.

The disadvantages of a Public Cloud are:

Wrong  Provider - There are very real hazards of picking the wrong provider for your public cloud. If they don’t keep the hardware that is running your applications up to date then your systems may suffer compliance and speed issues. Downtime is also more of a risk.

Lower Control - As the public cloud is controlled by an outside vendor organisations don’t often have as much control as they do if it were their own private cloud.

Perceived weaker security - Security is the downside to the public cloud, but, as is proven by the high level of public cloud adoption by some of the worlds biggest organisations the security concerns are often not valid if the public cloud is hosted by a secure vendor.

Private Cloud

Private CloudA Private cloud, which is also known as an internal cloud or enterprise cloud is for organizations who are seeking the same dynamic flexibility as a public cloud but don’t want to put their applications and data into a public cloud usually due to security concerns.

The definition of a private cloud is currently a bit of a grey area. Several different infrastructure instances are classed as a private cloud; from a environment hosted by an external vendor that is a completely unshared environment, through to environments hosted within the organisations own premises. In my opinion for the latter to be considered a true private cloud it has to be hosted and maintained by an external vendor, otherwise it isn’t a lot different from an on-premise infrastructure.

Another grey area of a private cloud comes in the application licensing model. Applications hosted on public clouds are generally done so with a SaaS licensing model, where as applications hosted on a private cloud are often not SaaS and therefore require capital expenditure and often expensive hardware and software upgrades over time.

The advantages of a Private Cloud are:

Security - The security is within the organisations control. Although whilst many are quick to credit private clouds as being more secure the vast array of different deployment types and levels of security within private hosting environments makes this an extremely bold statement. The reality for me is that a private cloud is just as susceptible to security risks as a public cloud. The only difference I see is that a public cloud may be more attractive to try and infiltrate than a private cloud as there is a wider amount of data on offer.

Performance - If a private cloud is deployed inside an organisations firewall it will increase the performance dramatically compared to using the internet to access a public cloud off premise.

More control and flexibility - Organisations are generally more in control of the private clouds and as a result organisations are able to deploy new applications and make changes more quickly.

The disadvantages of a Private Cloud are:

Additional Maintenance - If the private cloud is not maintained by the software vendor then it is unlikely that the organisation will benefit from the regular updates that are often associated with modern SaaS applications.

Higher cost - Everything relating to a private cloud is more expensive. Whether the organisation has to purchase the infrastructure or it’s still provided by the vendor this will be at a higher cost than a public cloud. On top of this regardless of whether the organisation manage the cloud or the organisation either will still cost more than the associated costs with a public cloud.

Hybrid Cloud

Hybrid CloudAs the name suggests a Hybrid cloud is a mix of both a public and private cloud. The hybrid cloud is harder to describe as so many different variations of the mix between private and public are possible. For example an organization may choose to place their working environments in a public cloud whilst the development environment may be placed in a private cloud. Also many organisations choose to run their sales and marketing operations in a public cloud, whilst keeping their financial operations within a private cloud. Another option is two run dual systems – 1 in the private cloud and 1 in the public cloud and then synchronise the two. This is a complicated process.


Despite the term being around for almost twenty years the definitions of different types of cloud are still not crystal clear. In particular in reference to private clouds where it is not defined whether the private cloud is on-premise or off-premise and who is responsible for the maintenance. I believe in the next few years we will see this become better defined.

Ultimately the decision with each cloud deployment will come down to two elements:- cost and control. Organisations will need to balance which is more important to them. If keeping costs low then a public cloud is the best fit but the organisation will have to sacrifice some control. Likewise a private cloud will give them more control but at a higher cost. Private cloud versus public cloud A hybrid cloud could provide the perfect compromise where for example an organisation can put their lower risk departments into a public cloud whilst the higher risk departments such as the office of finance are hosted privately within a private cloud.