Three Types of Cloud Computing: Private Cloud vs. Public Cloud vs. Hybrid Cloud

The public cloud is a computing model where services such as storage, servers, and applications are delivered over the internet or other networks by third-party providers, such as Amazon Web Services (AWS), Microsoft Azure, and Google Cloud. These resources are shared among multiple users, or "tenants," and are accessible on demand, typically through a pay-as-you-go pricing model. 

For organizations, the primary benefit of public cloud deployments is access to highly scalable and flexible computing resources without having to invest in and maintain physical data center infrastructure. The public cloud is ideal for workloads requiring rapid provisioning, global reach, or variable demand.

However, cloud computing’s pay-as-you-go pricing model means that costs can be steep with ongoing use.  Security can also be an issue, as cloud computing typically operates with a “shared responsibility” security model that divides security responsibilities between the cloud service provider (such as AWS or Google Cloud) and the customer. While the cloud provider is responsible for securing the cloud infrastructure (such as physical data centers, servers, and networking), the customer is responsible for securing what they put into the cloud—including applications, data, and workloads. The dynamic nature of cloud environments can make it challenging for the customer to track and enforce consistent security policies and controls in the cloud, while limited visibility into cloud workloads can make it difficult to detect anomalies or unauthorized access to customer data. Understanding where the provider’s responsibility ends and the customer’s begins is essential to avoiding breaches, compliance violations, and costly misconfigurations. 

In private cloud computing, cloud-based technologies, infrastructures, resources, and services are for the exclusive use of a single organization, which maintains a high level of control and security over the cloud resources. Unlike public clouds, which serve multiple tenants, a private cloud provides a dedicated cloud environment to provide greater control, customization, and security, making it attractive to organizations with specific performance or compliance requirements.

Key benefits of the private cloud model include enhanced security and data privacy, as the dedicated cloud resources mean no sharing of infrastructure with other organizations. This also leads to greater control over configurations and software, allowing the infrastructure to be optimized specifically for the organization's workloads, or to meet specific business needs.

Among the drawbacks of employing the private cloud model is the potential for higher costs, as on-premises private clouds require substantial upfront capital investments in hardware, software, and other IT resources. Ongoing expenses for operational costs, such as power, licensing, and maintenance, can also be high. Operating a private cloud on-premises also requires skilled IT staff to manage infrastructure, virtualization, security, and updates.

Private clouds come in several forms, depending on how and where the infrastructure is deployed and who manages it. 

• An on-premises private cloud is hosted entirely within an organization’s own data center and managed by its internal IT team, giving the organization complete control over its private cloud hardware, software, and data. This model is suitable for organizations with strict compliance or data sovereignty needs.
• A virtual private cloud (VPC) is a logically isolated environment within a public cloud resource (such as AWS) that uses network segmentation technologies like virtual private networks (VPNs) or virtual local area networks (VLANs) to emulate the security or compliance guarantees of a private cloud.
• Hosted private clouds are offered by third-party vendors, which dedicate cloud resources in their public data centers solely to one organization. This allows organizations to run workloads in an isolated environment while still taking advantage of public cloud IT infrastructure.
• A managed private cloud is a private cloud environment—on-premises or hosted—that is fully managed by a third-party service provider, which handles cloud setup, monitoring, maintenance, updates, and support. This allows organizations to take advantage of private cloud functionality without dedicating internal IT resources to cloud management.

Choosing between public cloud and private cloud models requires a careful evaluation of an organization's strategic goals, compliance requirements, budget, and the characteristics of specific applications and workloads.

Evaluation criteria should include:

• Data security. Do your applications leverage personal, financial, healthcare, or other sensitive data? Are there specific compliance requirements for certain data types or workloads, such as those required by HIPAA? Private clouds are recommended for highly regulated workloads that require strict access controls or data privacy.
• Scalability for traffic peaks. Do your applications need to support periodic traffic surges, such as holiday shopping, or unpredictable demand spikes? If so, the flexible usage model of the public cloud is optimal for highly dynamic workloads and data flows. 
• Data sovereignty regulations. Organizations operating in countries with data protection laws may face strict controls over how and where personal data is collected, stored, and transferred. Private clouds offer better control over data location, which makes them well-suited to meet data sovereignty requirements. Public cloud providers often operate global data centers that may replicate or move data across borders without explicit customer control.
• Responsiveness. Do most of your workloads demand low latency or high throughput, or is performance consistency critical? Do users expect near-zero latency at all times? Private cloud is ideal for performance-sensitive, latency-critical apps.
• Compute requirements. Are your applications required to process massive amounts of data, such as for big data analytics or generative AI, demanding massive storage and compute capacity? Public clouds are often the preferred choice for big data and AI workloads because they can scale compute and storage resources up or down elastically to accommodate the processing of large datasets, training AI models, or running batch analytics. 

While multicloud computing is a recognized cloud computing architecture or strategy, it is not a separate type of cloud computing. Multicloud refers to the use of multiple public cloud platforms from different providers to meet business or technical needs. For example, an organization might use AWS for some of its applications and Microsoft Azure for others. A multicloud architecture may happen incidentally (for instance, due to a merger of two companies that each use different public clouds) or result from a strategic decision to address differing business requirements and factors such as performance, business resiliency, and geographic location.

Community cloud is another cloud strategy or deployment model in which cloud resources are shared among a group of organizations with common requirements and a need to share data, such as government agencies or research organizations.  The difference between hybrid cloud and community cloud computing lies primarily in who shares the infrastructure, how it is used, and why it is used.