Public Cloud 
IBM Cloud Education
Tokyo skyline at Night
What is a public cloud?

Learn what a public cloud is and what it offers compared to—or together with—private cloud and hybrid cloud computing models.

The rise and adoption of public cloud services is one of the most important shifts in the history of enterprise computing. A public cloud is a type of cloud computing in which a third-party service provider makes computing resources—which can include anything from ready-to-use software applications, to individual virtual machines (VMs), to complete enterprise-grade infrastructures and development platforms—available to users over the public Internet. These resources might be accessible for free, or access might be sold according to subscription-based or pay-per-usage pricing models.

The public cloud provider owns and administers the data centers where customers’ workloads run. Service providers assume responsibility for all hardware and infrastructure maintenance and provides high-bandwidth network connectivity to ensure rapid access to applications and data. The cloud provider also manages the underlying virtualization software. In its simplest form, the public cloud model is the computing version of the “utility” model we all use when consuming electricity or water in our homes.

Public cloud architectures are multi-tenant environments—users share a pool of virtual resources that are automatically provisioned for and allocated to individual tenants through a self-service interface. This means that multiple tenants’ workloads might be running CPU instances running on shared physical server at the same time. Each cloud tenant’s data is logically isolated from that of other tenants, however.

The global market for public cloud computing has grown rapidly over the past few years, and analysts forecast that this trend will continue; Gartner (link resides outside predicts that worldwide public cloud revenues will exceed $330 billion by the end of 2022.

Many enterprises are moving portions of their computing infrastructure to the public cloud because public cloud services are elastic and readily scalable, flexibly adjusting to meet changing workload demands. Others are attracted by the promise of greater efficiency and fewer wasted resources since customers pay only for what they use. Still others seek to reduce spending on hardware and on-premises infrastructures.

Check out the following video for more info on public cloud:

Public cloud services

A broad array of public cloud computing services are available today, comprising multiple offerings and service models. Almost any service that doesn’t require physical proximity to the hardware that’s hosting it can now be delivered via the cloud.

The three most common cloud service models are as follows:

  • Infrastructure-as-a-Service (IaaS): In IaaS, the public cloud provider offers access to fundamental compute, network, and storage resources on demand over the public Internet or through dedicated connections. This might consist of direct access to the underlying hardware—a model known as bare metal—but more commonly, it’s access to already virtualized resources.    
  • Platform-as-a-Service (PaaS): PaaS provides application developers a complete platform—including all necessary hardware, software, and infrastructure—upon which applications can be built, run, and managed. The entire platform infrastructure is typically managed by the cloud provider, and users need not worry about lower-level details.  
  • Software-as-a-Service (SaaS): With SaaS, users receive access to cloud-hosted software applications. Instead of being installed on local devices, these applications reside in the cloud and are accessed through a web browser or via an API.

Other service models (which are often more specialized) are also available. These include offerings like Business-Process-as-a-Service (BPaaS), in which an entire horizontal or vertical business process is delivered together as a combination of related IaaS, PaaS, and SaaS services; or Function-as-a-Service (FaaS), a subset of SaaS in which application code runs only in response to specific events or requests. The vast majority of these offerings, however, are subtypes or extensions of the three basic cloud computing service models.

Public cloud vs. private cloud

Private cloud is cloud infrastructure operated exclusively for one company. Typically, a private cloud is hosted on-premises, behind the client company’s own firewall, but it can also be hosted on dedicated cloud provider or third-party infrastructure. In either event, the client company has exclusive, isolated access to the infrastructure.

Private cloud enables a company to take advantage of cloud efficiencies while providing greater control over resources, data security, and regulatory compliance, and avoiding the potential performance and security impact of sharing resources with another cloud customer.

One popular analogy likens private cloud computing to owning a single-family home and public cloud computing to renting an apartment or condominium in a multi-unit building.

In private cloud, the customer is typically responsible for managing and maintaining the infrastructure, which includes capacity planning to ensure that the available hardware can meet present and future needs, software licensing and installation, and monitoring and enforcing security policies.

Some possible advantages of private cloud compared to public cloud include the following:

  • Greater ability to customize applications and infrastructure.
  • Greater control and security because workloads run behind the tenant’s firewall, though overall security is dependent upon that of the tenant’s own environment.
  • Simplified (or simplified perceived) compliance with industry or government regulations.

Private cloud typically involves higher up-front and ongoing costs than public cloud. But emerging public cloud offerings such as virtual private clouds (VPCs) bring many of the same benefits as private cloud computing without imposing the same cost or management burdens. And new private cloud offerings such as managed private cloud services—in which a third-party vendor steps in to deploy, configure, and manage the private cloud on the customer’s behalf—are also making private cloud-like services easier to consume.

In general, public cloud is a better choice if the following are true:

  • Scalability and elasticity—the ability to add capacity instantly or automatically in response to unexpected surges in traffic—are important to you.
  • You’d like to avoid upfront capital expenses and prefer more predictable ongoing operating expenses.
  • You want unlimited access to particular resources that are available through a public cloud provider.

However, if you have highly specialized security, regulatory, or infrastructure needs, want maximum control over your cloud environment, and find that your workloads have predictable usage patterns, a private cloud or private cloud-like service could better a good fit.

Public cloud, private cloud, and hybrid cloud

Hybrid cloud integrates private and public clouds, using technologies and management tools that allow an enterprise to move workloads seamlessly between both as needed for optimal performance, security, compliance, and cost-effectiveness.

For example, hybrid cloud enables a company to keep sensitive data and mission critical legacy applications (which can’t easily be migrated to the cloud) on-premises while leveraging public cloud for SaaS applications, PaaS for rapid deployment of new applications, and IaaS for additional storage or compute capacity on demand.

The majority of enterprise cloud adopters turn to hybrid cloud architectures so that they have the flexibility to choose the best cloud environment (public or private) for each of their workloads or move the workloads between clouds as their needs change.

For more background on hybrid cloud, see our video “Hybrid Cloud Explained”:

Public cloud security

Traditionally, security concerns have been the number-one obstacle for organizations considering public cloud. In response to demand, however, the security offered by cloud service providers is steadily outstripping on-premises security solutions.

With the growing popularity of containers—which can greatly enhance security in cloud native application architectures—and new public cloud offerings that include vendor-certified compliance with industry standards and regulations, it’s becoming easier than ever to maintain a security posture that’s at least as strong as what can be achieved with on-premises infrastructures.

According to security software provider McAfee, today 52% of companies experience better security in the cloud than on-premises. (link resides outside of Gartner has predicted that by this year (2020), infrastructure as a service (IaaS) cloud workloads will experience 60% fewer security incidents than those in traditional data centers (PDF, 2.3 MB) (link resides outside of

Nonetheless, maintaining such security standards in the public cloud demands different governance procedures and employee skillsets than in legacy IT environments. Cloud security requires strong access management, encryption for data at rest, in transit, or in use, and excellent visibility to monitor, detect and manage cyberthreats.

Public cloud and IBM Cloud

IBM Cloud supports over 1,000 enterprise clients, providing them with access to the industry’s leading security infrastructure, which includes built-in workload isolation and network segmentation along with continuous container security and end-to-end data encryption.

The IBM public cloud was built on an open source software foundation. IBM Cloud employees have been major longtime contributors to key cloud native and open source projects including KubernetesIstio, and Knative. The strength of IBM’s commitment to the open source ecosystem provides its cloud customers with flexible developer tools and access to resources without vendor lock-in.

Working with Red Hat, IBM Cloud has introduced a managed Red Hat OpenShift environment on the IBM public cloud that has quickly become the number-one open source solution for customers looking to simplify the management of their container-based architectures and speed development pipelines.

IBM also provides continuous edge-to-cloud support for hybrid workloads, whether they’re VMware-based, built to run on bare metal servers, or cloud native. IBM Cloud incorporates robust data protection and visibility features to protect information throughout the whole of its lifecycle, no matter where it resides.

Built with Red Hat OpenShift, IBM Cloud Satellite addresses how building, deploying and managing applications across multiple cloud environments can degrade application performance. Satellite offers a fully managed set of core application services that run across cloud environments including IBM Cloud, on-premises and edge. You operate development processes, methods and tools in a single and consistent way across all types of cloud environments, including those of other public cloud vendors.

To learn more about what’s it’s like to build on IBM Cloud, you can get started for free by signing up for an IBM Cloud account today.

Keep the conversation going. Join your peers in the public cloud community.

Related solutions

IBM Cloud

IBM Cloud with Red Hat offers market-leading security, enterprise scalability and open innovation to unlock the full potential of cloud and AI.

Open cloud

IBM open cloud is built on the best of open source technology.

Red Hat OpenShift on IBM Cloud

Red Hat OpenShift on IBM Cloud leverages OpenShift in public and hybrid environments for velocity, market responsiveness, scalability and reliability.

IBM Cloud Satellite

With IBM Cloud Satellite, you can launch consistent cloud services anywhere — on premises, at the edge and in public cloud environments.