Public Cloud vs Private Cloud: What is the Difference?

The key difference between public and private cloud computing relates to access. In a public cloud, organizations use shared cloud infrastructure, while in a private cloud, organizations use their own infrastructure. To fully understand which cloud environment organizations should use, it is important to understand each environment in-depth, as well as their advantages and disadvantages.

What is a Public cloud?

In a public cloud model, cloud services and resources are offered through a third-party cloud service provider (CSP) and delivered via the internet through a subscription model, such as platform-as-a-service (PaaS), infrastructure-as-a-service (IaaS) or software-as-a-service (SaaS). In this model, all hardware, software, and other supporting cloud infrastructure are owned, operated and maintained by the cloud provider and shared with other users. Examples of public clouds include Amazon Web Services (AWS), Microsoft Azure and Google Cloud Platform (GCP).

The public cloud operates on the principle of multi-tenancy, which means that multiple organizations, or “tenants”, have access to the same cloud infrastructure and computing resources, such as servers and cloud storage.

What is a Private Cloud?

A private cloud, which is sometimes referred to as an on-premises private data center, is a cloud computing model where one organization has exclusive use of the cloud, its services and associated infrastructure. While a private cloud may still be hosted by a CSP, it is dedicated to just one user and resources are never shared.

Private clouds are most often used by organizations that require customizable and highly secure IT environments. For example, private clouds are often used by government agencies, hospitals, or financial institutions, which maintain sensitive data and are subject to strict compliance standards.

Public vs Private Cloud: Advantages

Public Cloud	Private Cloud
Cost savings: In a public cloud model, organizations generally have lower IT costs because they do not need to purchase, operate or maintain hardware or software. Further, most cloud computing plans are based on consumption pricing, which means that organizations only pay for the resources they use.	Privacy As the name implies, the private cloud is not shared with other tenants, which means that a single tenant has complete control over the cloud environment.
Limited maintenance: The public cloud provider is responsible for all maintenance of the cloud environment and associated assets.	Security: Because the private cloud is not shared with any other users, this network tends to provide far greater control, privacy and security — as long as the user has adopted a comprehensive security strategy specifically designed for the cloud.
Scalability: Organizations that use the public cloud have virtually infinite cloud computing resources available on demand and can easily scale workloads up or down based on business needs.	Customization: In a private cloud model, organizations have complete control of their cloud environment and can customize their network to meet the organization’s business needs or comply with regulatory standards.
Reliability: Public cloud workloads can be quickly moved from one server to another in the event of a failure or other performance issue.	Performance: Because the private cloud is not a shared resource, most users benefit from higher performance.
Business Focus: Because a public cloud creates less need for maintenance and IT expertise to manage infrastructure, they can focus on other business priorities.	Flexibility: As your infrastructure changes based on business needs, a private cloud can keep up with it without an issue.

Public vs Private Cloud: Disadvantages

Public Cloud	Private Cloud
Security: The public cloud model follows what is known as The Shared Responsibility Model. This means that while a third-party service provider monitors and responds to threats against the cloud infrastructure, they are not responsible for securing each customer’s data, applications, workloads, or operating systems. That effort belongs to the customer alone. Many customers may not realize their role in the Shared Responsibility Model, nor have they adopted strong cybersecurity practices specific to the cloud. Further, since the public cloud is a shared resource, companies that use it are also subject to security risks created by other tenants.	Cost: Using a private cloud is almost always more expensive than using a public cloud because the organization either has to build and run their own network, or pay a third-party to do so on their behalf.
Compliance: Some organizations face strict regulatory compliance standards that may be difficult or impossible to meet in a public cloud environment due to the multi-tenancy issue.	IT burden: Most private cloud users require significant IT resources for setup, operation and maintenance of the cloud environment.
Vendor reliance: While the public cloud offers most organizations significant cost savings in the near term, over time the organization will come to rely on their chosen cloud vendor to maintain business operations. As a result, the business may experience vendor lock-in, even if rates increase.	Scalability: Private cloud users cannot scale or shift workloads between cloud environments as easily as public cloud users, which makes it difficult for organizations to introduce new services rapidly. However, the private cloud model offers enhanced scalability as compared to traditional on-premises infrastructure.
Migration: For many companies, migrating to the public cloud can be a complex and time-consuming process that requires significant resources. Further, since most public cloud models offer a pay-what-you-use billing model, organizations must be judicious about what data, applications, and services they intend to host in the cloud.	Remote access: In most private cloud environments, remote access, as well as mobile access, is limited. Given recent workforce trends, as well as the effects of the COVID-19 pandemic, most private cloud networks do not support the needs of the modern workforce.
Lack of Cost Control: As companies grow in size, cloud usage increases, which in a public cloud, it becomes expensive due to full control over it.	Mobile Access: Because there are strong security measures protecting the private cloud, it is hard for mobile users to access it.

What is a Hybrid Cloud

Because private and public cloud models offer inherent advantages (and disadvantages), many organizations are increasingly turning to a hybrid cloud model, which is an IT environment that combines elements of a public cloud, private cloud and on-premises infrastructure into a single, common, unified architecture. In a hybrid cloud environment, organizations have the option to run and scale workloads in the optimal setting, as well as the flexibility to move workloads between different environments quickly and easily.

For example, with a hybrid cloud model, organizations are able to leverage the public cloud for high-volume, low-risk activity, such as hosting web-based applications like email or instant messaging. Meanwhile the private cloud can be reserved for functions that require greater security, such as processing payments or storing personal data. In so doing, the organization is able to capitalize on the cost savings of a public cloud while also maintaining a higher level of security or compliance for select functions.

Advantages of a Hybrid Cloud Environment

With a hybrid cloud model, many organizations can get the “best of both worlds”. Advantages include:

• Flexibility: A hybrid cloud computing model allows the organization to run a workload in the optimal environment, as well as shift that workload based on capacity, demand or costs.
• Cost Efficiency: In a hybrid model, organizations can optimize their costs by selecting the best computing environment for each task.
• Elasticity: A hybrid cloud environment is dynamic, meaning that resources can quickly be adjusted and reallocated based on current needs. Further, in the case of unexpected surges in demand, the business can manage such spikes through a public cloud service.
• Business Agility: A unified hybrid cloud platform can help expand adoption of Agile and DevOps methodologies, which in turn can help speed time to market.
• Enhanced Security and Compliance: A unified hybrid cloud platform helps the organization take a holistic approach to cybersecurity and regulatory compliance. Since the organization is operating in a single IT environment, companies can develop a comprehensive strategy and deploy tooling consistently across the entire environment. A hybrid cloud approach also ensures that the organization properly hosts sensitive information, such as customer data or patient records, in a private cloud environment as dictated by government regulations or industry guidelines.

Hybrid Cloud vs. Multi Cloud

Though sometimes used interchangeably, hybrid and multi-cloud environments are two distinct models.

In short, a hybrid cloud creates a single environment consisting of public, private and on-prem infrastructure elements and services. A multi-cloud environment, on the other hand, unites two or more public cloud instances but does not integrate private cloud services or an on-prem component.

Based on this definition, it is possible for a hybrid cloud model to also be a multi-cloud model if the environment incorporates private cloud, on-prem and more than one public cloud instance.

Questions to Ask when Choosing a Deployment Option

As discussed above there are four main cloud deployment options:

1. Public cloud
2. Private cloud
3. Hybrid cloud
4. Multi-cloud

Organizations interested in shifting to a cloud-based business model will need to consider which deployment option best meets their needs. Some key considerations include:

Security

Every cloud environment has unique security challenges.

• Which aspects of the cloud environment will the organization be responsible for?
• Does the business have the necessary expertise and resources to maintain strong cloud security standards?
• How will the organization adjust its security strategy to protect cloud-based assets?

Regulatory compliance

• What industry or government regulations is the organization subject to?
• Does the preferred cloud model comply with those needs?
• Can the organization adopt a hybrid cloud strategy and shift certain services to a public cloud model while maintaining others in a more secure environment?

Scalability

• What are the organization’s near-term plans and how can the environment evolve to support those goals?
• Is speed and flexibility critical to the organization’s go-to-market strategy?

Reliability

• In the event of a network failure, how will services and workloads be impacted?
• Can the organization tolerate brief service interruptions?

Cost

• What is the cost associated with each of these models?
• What impact will the decision have on the business’s current IT organization?

Complexity

• How does shifting to the cloud impact business operations?
• How will the organization mitigate complexity related to the cloud migration?

Remote access

• Does the business need to support a remote or mobile workforce?
• Does the organization intend to allow remote work in the future?