There are four separate cloud deployment models: public clouds, private clouds, hybrid clouds, and multi-clouds. When planning cloud adoption, one of the first steps is to determine which deployment option is right for the organization. Deployment options are not cast in stone, an organization can switch from one to another as business and technology needs evolve.

What are public cloud deployments?

Public clouds are shared, on-demand infrastructure and resources delivered by a third-party provider. In a public cloud deployment the organization utilizes one or more types of cloud services such as software-as-a-service (SaaS), platform-as-a-service (PaaS) or IaaS from public CSPs such as AWS or Azure, without relying to any degree on private cloud (on-premises) infrastructure.

Younger organizations said to be ‘born in the cloud’ utilize public cloud services from their inception and have no reliance on legacy infrastructure or outdated applications. A public cloud deployment option is also common among smaller companies that have neither budget or manpower to staff an in-house data center or private cloud.

What are private cloud deployments?

A private cloud is a dedicated, on-demand infrastructure and resources that are owned by the user organization. The terms private cloud and on-premises data center are often interchangeable.

Private cloud deployments are operated by the business, who is solely responsible for the infrastructure, applications, and security of the private cloud. Users may access private cloud resources over a private network or VPN; external users may access the organization’s IT resources via a web interface over the public network. Private clouds are often utilized to ensure compliance with regulatory or governance demands, to ensure security protocols are followed, or to leverage an existing investment in IT infrastructure. Large enterprises can operate their IT as if it were a cloud provider, offering IT services to line of business (LOB) departments, self-service provisioning for development teams, and charging back user departments for private cloud services rendered to the LOBs. Operating a large datacenter as a private cloud can deliver many benefits of a public cloud, especially for very large organizations.

What are hybrid cloud deployments?

A hybrid cloud is a combination of public cloud and private cloud services, working together to deliver consistency across operations and infrastructure. Hybrid cloud deployments always have public and private components by definition.

Hybrid cloud deployments server many purposes and their usage continues to grow. Organizations who wish to migrate to a public cloud deployment often take a hybrid approach, first migrating those workloads that are the least ‘sticky’, for example front-end applications that do not process sensitive information that is stored in on-premises private cloud servers. Over time, an increasing number of applications can be migrated while legacy applications are refactored to take advantage of modern application development and deployment techniques.

Hybrid deployments also offer elasticity and scalability. For example a retailer who experiences a sharp growth in accesses due to the holiday season can elastically scale its web servicing front end from private to public cloud servers by rapidly spinning up new instances. In this way spikes in demand can be quickly satisfied without the need to procure extra infrastructure for the holiday rush, or to overprovision and have that infrastructure sit idle for most of the year.

What are multi-cloud deployments?

A multi-cloud is any combination of one or more public clouds and private clouds.

Many organizations rely on more than one public cloud provider. For example, they might use Azure for exchange and database servers, AWS for hosting virtual machines and newly refactored code running in containers, and Google Cloud Platform for collaboration and office productivity tools.

In many cases, organizations ‘accidentally’ adopt a multi-cloud deployment when individual user departments procure their own cloud services without IT knowledge, or when a merger or acquisition brings a new provider into the enterprise cloud fold.

Also, since each CSP’s offering vary organizations can pick and choose from a menu of services provided by each provider to craft a computing strategy perfectly tailored to their needs. Finally, some organizations are using cloud arbitrage to match needs to the CSP offering the best deal at that point in time. By leveraging multi-cloud orchestration tools such as Kubernetes these organizations can seamlessly migrate application workloads from one cloud provider to another and back again with absolutely no impact on user performance or uptime.

Finally, there can be a combination of deployment models. Organizations can be both multi-cloud and hybrid cloud if they utilize multiple CSPs as well as their own private cloud.