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 ibm.com) predicts that worldwide public cloud revenues will exceed USD 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:
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:
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.
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:
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:
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.
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”:
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 ibm.com) 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 ibm.com).
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.
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Hybrid cloud combines and unifies public cloud, private cloud, and on-premises infrastructure to create a single, flexible, cost-optimal IT infrastructure.
Understand and compare the three most popular cloud computing service models.