The Different Cloud Deployment Models Explained

In recent years, the concept of Cloud Computing has become integral to the modern IT landscape. Many organisations have adopted a “Cloud First” strategy where any new deployments must be hosted in “The Cloud”. The Covid-19 pandemic accelerated this trend as organisations tried to take advantage of cloud services to facilitate working from home arrangements during the frequent lockdowns.

However, what do people mean when they talk about The Cloud? There is still a lot of confusion about what the term means and what you can really expect in any given scenario. Today we’re going to take a look at the different types of Clouds that are available and the benefits and use cases of each one.

What are the different cloud deployment models?

Public Cloud

When referring to the Public Cloud, what we’re really talking about is computing services that are offered by a third-party provider over the public internet. They will allow the customer to only pay for their exact resource usage for things like CPU cycles, storage, or network bandwidth consumed.

In a Public Cloud, the hardware, software and network devices are shared between multiple different companies. We refer to these as “Cloud Tenants” and they have access to services and management of their tenancy through a web browser, terminal or an API.

The service provisions in a Public Cloud are categorised in one of three ways:

• SaaS: Software as a Service
  This is a way of delivering centrally hosted applications over the internet as a service. This removes the need to install, maintain and manage the underlying hardware, Operating Systems (OS), software and surrounding infrastructure. Examples include Microsoft Office 365 and Google Workspace.
• PaaS: Platform as a Service
  This delivery method involves the Cloud Provider hosting, managing and maintaining all hardware and software included in the platform. This includes OS and middleware, development tools and business intelligence along with all upgrades, updates and security patching. Examples include AWS Elastic Beanstalk and Google App Engine.
• IaaS: Infrastructure as a Service
  This is the service model that most closely aligns to the more traditional Virtualisation that most companies operate in their On-Premise data centres. The cloud tenant can provision, configure and use compute, storage and network capacity to create Virtual Machines (or in some cases, Bare Metal). These were the services that providers like Microsoft Azure and Amazon Web Services offered when they started.

Public Clouds operate under a shared responsibility model. This means that, depending on the service type you consume, you will be responsible for different things.

There are a multitude of benefits of using a Public Cloud:

• Agility
  When talking about Cloud Agility we are specifically addressing the ability to quickly react to business needs and consume resources as required. The ability to react quickly is something that has traditionally been hampered by long procurement times and prohibitively high upfront costs. The cloud allows you to spin up a service immediately and only pay for those services that you actively consume.
• Elasticity
  Outside of a cloud environment, an organisation would design their systems to have excess capacity to cover whatever their peak forecast load would be – i.e. seasonal workloads around peak website sales dates. The use of cloud resources allows an IT department to only provision what they need, scale up to cover the abnormal workload, then scale back down to only the required capacity which avoids having to pay for unused resource for the majority of the time.
• Scalability
  Scalability goes hand in hand with Elasticity. Whereas Elasticity is the ability to automatically scale up and down, scalability is having the available resource and capacity to do so.

Private Cloud

There are a lot of similarities between a Public and Private Cloud. However, instead of compute, storage and network resource being provisioned to multiple tenants as a shared pool, Private Cloud services are used exclusively by one organisation. This could be in an On-Premise or Co-location facility, or it could be hosted entirely by a Third Party Provider but the defining characteristic is that it is on a private network with hardware and software dedicated solely to your organisation.

The benefit of this is that you have much more granular control over what happens at the hardware and software layer. If your organisation has a specific need that must be addressed, a Private Cloud gives you much greater flexibility to design and deliver a bespoke service.

Another benefit is that you can control factors such as contention levels and service placement to make sure that you’re optimising the performance of the underlying resources.

One negative aspect of a Private Cloud is that the organisation (or nominated service provider) retains responsibility for the operational overhead of running a Private Cloud. All of the hardware and OS infrastructure needs to be supported, maintained and patched which has an impact on staffing considerations whilst sufficient capacity needs to be provisioned upfront in order to make sure there is no impact on services during maintenance windows or hardware failures.

For a Private Cloud deployment to be different from a traditional On-Premise data centre deployment, it must still provide the three benefits previously attributed to Public Cloud: Agility, Elasticity and Scalability. Another defining feature is that the ability exists to interact with the environment programmatically to deliver increased automation and flexibility.

Hybrid Cloud

A Hybrid Cloud deployment combines the two types of deployment previously discussed; Public and Private Cloud (or On-Premise Infrastructure) deployments are used together in order to allow data, applications and functions to move between the two environments.

This is often described as the “best of both worlds” as you get the increased control for a subset of workloads by hosting them on a private infrastructure but also have the ability to take advantage of the scalability and redundancy offered by a Public Cloud infrastructure as required.

The increased control is particularly important for industries that have strict regulatory and data sovereignty requirements. They can store the data locally whilst having greater levels of oversight and control, but utilise the resources of a Public Cloud provider to scale up access during times of heavy load without having to give them full access to their data.

Another big driver for Hybrid Cloud is for latency sensitive applications and functions. By utilising a hybrid cloud approach, you can bring your compute and storage closer to your workloads to avoid having to communicate with a Public Cloud – this is something which is often referred to as Edge computing.

Multicloud

The final term that is often used is Multicloud. At first glance this appears to be similar to Hybrid Cloud, however, it is generally used to refer to multiple cloud deployments of the same type as opposed to Hybrid which is multiple cloud deployments of different types.

For example, a deployment that spanned 2 Public Clouds would be classed as Multicloud, the same is true of a deployment spanning 2 Private Clouds. However, a deployment that spanned 1 Private Cloud and 1 Public Cloud would be Hybrid.

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