Defining the Cloud: Public vs Private vs Hybrid

The ultimate goal of cloud computing is ubiquity – where the services work so well they are just part of the everyday business processes. Cloud computing has finally matured but there is still progress to be made. To reach the goal businesses still need to be educated on the kinds of cloud services they can choose. The biggest question is often whether a public or private cloud or a combination of the two, a hybrid cloud, is the right choice.

Public Cloud

A public cloud is open to the general public and delivered over shared infrastructure. Amazon EC2, Microsoft Azure and Google Compute Engine are examples of large-scale public cloud offerings. With these types of cloud you can sign-up online very quickly, choose the resources you need and swiftly deploy a virtual infrastructure.

Possibly the biggest concern over a public cloud is security and data privacy.

Public cloud offerings are typically very cheap and have very much become a commodity-based service, offering a one-size-fits-all solution where you have little say in the technological infrastructure. They are ideal for companies who have a basic need for infrastructure but don’t require their solution to be tailored to any specific requirements they may have.

Support is often limited and management is rarely provided, so a public cloud provider is usually more suited to organisations that have a high degree of technical knowledge in-house.

Possibly the biggest concern over a public cloud is security and data privacy. You will probably never know exactly where your data is being hosted and so to what laws it is subject to, such as the Patriot Act in the USA. Because of this, data sovereignty is an increasingly prominent issue and many customers are opting for public cloud providers based in the UK or EU. Also, the use of shared infrastructure means you don’t know who your digital neighbours are – and if they are behaving poorly it can have knock-on effect to the performance and reliability of your solution.


  • Usually cheap
  • Simple sign-up process
  • Quick to deploy a virtual infrastructure
  • Quick and easy to scale resources


  • Not ideal for applications that require high security or transmit/store sensitive data
  • Limited ability to tailor a solution to your requirements
  • You need to have a high degree of technical knowledge in-house
  • Limited support and management


  • Software development test environments
  • Hosting applications that don’t require data security or legal requirement to know exactly where data is hosted

Private Cloud

As the name suggests, a private cloud is a cloud deployment where infrastructure is completely private to the organisation using it. This is the opposite philosophy to a public cloud, where the infrastructure is shared amongst multiple companies.

Typically, private cloud providers allow the environment to be tailored to your exact requirements, meaning you can have free choice on hardware vendors used to make up your private cloud platform. There would normally be collaborative design consultations between you and the cloud supplier to ensure environment is optimally configured to meet your needs.

With a private cloud solution you can be sure that no one else is using your infrastructure, boosting performance and reliability. You also have control over where your data is stored which increases security and privacy. For organisations with sensitive data, data privacy and data sovereignty can be a vital consideration.

Private clouds will often come with a tailored Service Level Agreement (SLA), an added level of support and the option of partial or full management – reducing the burden on your in-house technical team.

The downside to a private cloud is usually the cost, as your service provider will need to make its money back on the investment into all of the dedicated components used to make up your private cloud.


  • Can be tailored to your exact requirements
  • Extremely secure – you know exactly where your data is
  • Dedicated Resources – 100% of resources guaranteed to be available for your use only
  • Enhanced Service Level Agreement


  • Cost – can be price prohibitive for smaller organisations
  • Resources are fixed and cannot be easily flexed up without adding more physical capacity


  • Hosting mission-critical applications
  • Hosting applications or storing data that requires a high level of security
  • Requirements that need a completely bespoke solution put in place

Hybrid Cloud

A hybrid cloud is, as you might expect, a blend of private and public cloud infrastructures. This hybrid approach combines the advantages of the scalability and cost-effectiveness of a public cloud with the dedicated resources and power of a private infrastructure.

By way of an example, a typical hybrid cloud deployment might be hosting your key live environment (such as an Exchange or SharePoint) within a private cloud, but sending archive data to the public cloud where you could make use of lower-cost and lower-performance storage.

Another example: you might need guaranteed server resources for an important application or for database which for performance reasons can’t be virtualised and therefore needs to be completely private. This would rule out a traditional public cloud, but with a hybrid deployment you could use a public cloud infrastructure for other elements that could still be virtualised.

In the examples above you would probably want to encrypt the data on anything stored on a public cloud and inter-cloud latency would have to be considered so it doesn’t degrade your performance.

The hybrid approach really works better when using a Virtual Private Cloud (VPC) within the same data centre (or at least one quite local), instead of a public cloud because of the potential latency issues. For example, most of Amazon and Microsoft services are hosted in Dublin, so if your private cloud is located in the UK you’re more than likely going to run into latency issues.


  • Offers the advantages of the best parts of a public and private cloud
  • Offers a more flexible approach to managing your IT
  • Less expensive than a private cloud


  • More expensive than a public cloud
  • Can be more complicated and time consuming to set-up


  • For companies who prefer to maintain more control over their IT by using a private cloud, but are willing to use a public cloud for less mission–critical activities
  • For larger companies who have multiple applications, some of which can be run in a public cloud and others which must stay private owing to, for example, information governance

Virtual Private Cloud (VPC)

It is worth just touching on the benefits of a VPC because it is an extremely valid option which is often overlooked. In many respects a VPC is like a public cloud: it is still a shared multi-tenanted environment, but usually comes with a number of enhanced security features to ensure maximum security is provided. In my opinion a true VPC should be able to provide complete segregation between customers and be able to guarantee key resources (such as RAM).

It’s also my belief that if any infrastructure is going to be truly private, people shouldn’t just be able to sign-up online with a credit card and start using it. As a VPC is essentially still a multi-tenanted environment I believe it’s important to carry out background checks on the customers before on-boarding them, thus avoiding any high-risk entities being hosted which potentially could attract the wrong kind of attention.


  • Much lower cost than a private cloud
  • Provides all the benefits of a public cloud, but with increased security and control
  • Ideal for deploying within a hybrid cloud environment, where everything must remain private


  • More costly than a public cloud, but probably less so than you may think


  • Perfect for environments where privacy or security is of great importance.
  • Hosting applications which may require a more tailored solution than a public cloud can offer, but without the higher cost of a fully private cloud

There is no golden rule as to which type of cloud environment is best: each platform has its positive and negative points. They all have their place. For me it really comes down to understanding your own needs and balancing these against the budget you have. For most businesses understanding the benefits of public, private and hybrid clouds is a great start – making it easier to choose a cloud provider with the right cloud services to suit your requirements. Each choice has clear benefits.

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