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What Is a Public Cloud?

A public cloud is a cloud service provided by a third-party provider for users through the Internet. Users can access the cloud and enjoy various services, including but not limited to computing, storage, and network services. Public cloud services can be free of charge or charged by usage.

Features and Values of a Public Cloud

A public cloud aims to provide shared resources. Third-party providers provide customers with shared computing, storage, and network resources on demand. Customers can enjoy IT services in pay-per-use mode without initial IT infrastructure investment, significantly reducing the digitalization threshold and IT costs.

For most small- and medium-sized enterprises or startups, a public cloud is the best choice.

  • Operation: Enterprises can use services provided by the public cloud on demand in pay-per-use mode, reducing the total cost of operation (TCO). Especially for small- and medium-sized enterprises that do not have sufficient budget for device purchase, they may want to use and release resources in a short period of time in some scenarios, for example, testing and verification scenarios, and may require ultra-large-scale computing capabilities. These requirements can be met by the public cloud.
  • O&M: Enterprises used to build their own data centers (DCs) to support their services. DC construction involves infrastructure (including wind, fire, water, and electricity facilities, servers, storage devices, switches, and firewalls), systems, and middleware services. The infrastructure maintenance is complex and the expenditure is huge. By using the public cloud, enterprises only need to focus on their own services without paying attention to infrastructure construction. This greatly reduces maintenance complexity and maintenance costs, and enables the enterprises to focus on continuous service innovation.
  • Service: The public cloud provides various services for customers.
  • Security: Mainstream public cloud service providers can provide security levels that cannot be achieved by most enterprises. The provided public cloud services have passed most security and privacy certifications, which can effectively ensure the security of user data and privacy.

Public Cloud Architecture

The following figure shows the common architecture of a public cloud, including Infrastructure as a Service (IaaS), Platform as a Service (PaaS), Software as a Service (SaaS), O&M, operation, and security.

  • IaaS: abstracts computing, storage, and network resources, provides the abstracted resources for users, and provides corresponding services based on actual application requirements.
  • PaaS: provides users with container and microservice development services based on the IaaS layer.
  • SaaS: mainly provides scenario-based applications for users.
  • O&M: The public cloud provides user-oriented and platform-oriented O&M capabilities. The O&M capabilities available to users include permission control, performance monitoring, status monitoring, and fault alarm reporting. The platform O&M is performed by the public cloud assurance team to ensure high reliability, availability, and security of the platform.
  • Operation: The public cloud provides user-oriented and platform-oriented operation capabilities. The operation capabilities available to users include submitting work orders and order and billing, helping users understand operation costs and analyze service trends. The public cloud operation team processes and controls users' work orders and investments, and performs visualized management on the overall revenue of the public cloud.
  • Security: The public cloud needs to meet the requirements of system security, platform security, O&M security, and network security to ensure the security of data assets of users and cloud service providers.
Common public cloud architecture
Common public cloud architecture

Comparison Between Public and Private Clouds

Enterprises can deploy cloud computing services in three modes: public cloud, private cloud, and hybrid cloud. A private cloud is constructed by an enterprise and is exclusive to the enterprise. It can be deployed in the DC of the enterprise or the equipment room of a cloud platform service provider.

Overall Comparison

Compared with a private cloud, a public cloud has the following advantages:

  • Higher flexibility and scalability: With the public cloud, customers can quickly purchase computing, storage, and network resources to cope with surging service requirements without purchasing and deploying new hardware.
  • Lower costs: Most customers can use public cloud services without adding any physical infrastructure.
  • Faster access to the latest technologies: In many cases, public cloud providers can provide the latest hardware and software and upgrade them more quickly.

Compared with the public cloud, the private cloud has higher security but higher costs. In addition, the average utilization of the private cloud infrastructure is lower than that of the public cloud.

Construction and Operation Modes

  • The public cloud mode is a new IT capability consumption mode. It enables users to focus on the capabilities and SLAs of cloud services instead of paying attention to the resource locations, construction, delivery, and O&M. Users can quickly rent resources to deploy their own services, lowering the initial investment costs and shortening the service TTM. In terms of O&M, public cloud providers deliver most O&M services, and public cloud users only need to focus on their own applications.
  • Private cloud assets belong to the organization that builds the cloud. The organization takes the lead in building, managing, and maintaining the cloud and deploys the cloud in the DC. A private cloud requires high initial investment and a long construction and commissioning period. The O&M of the private cloud needs to be performed by the organization.


Generally, the IaaS and PaaS capabilities of a private cloud are part of those of a public cloud. The private cloud is constructed to meet the specific service requirements of an organization. Therefore, only the IaaS and PaaS capabilities required by the organization need to be deployed. For example, if the organization uses only the VM service rather than the BMS service, the BMS service does not need to be deployed in the private cloud.

In addition to IaaS and PaaS, the public cloud also provides SaaS, operation, and other key capabilities.

  • A public cloud typically provides the SaaS capability, which however may not be deployed in a private cloud. If the SaaS software is deployed in a private cloud, the private cloud owner needs to consume a vast number of resources to maintain the SaaS software. As such, the use of the SaaS capability in a private cloud causes high costs. Actual SaaS deployment depends on the customer's requirements in terms of security, cost, maintenance, and so on no matter whether SaaS is deployed in a public, private, or hybrid cloud.
  • A private cloud does not involve operation because the use of the private cloud is not charged within the organization. A public cloud must provide the operation capability because the public cloud provider needs to charge users in various modes.

Service Type

  • Non-core services, services that require fast iteration, and external services are deployed in the public cloud.
  • Core services and services requiring high information security levels of an organization are deployed in the organization's private cloud.

The following table lists the differences between the public and private clouds.


Public Cloud

Private Cloud

User type

Startups, small enterprises, and individuals

Government agencies and large enterprises

Service type

External services

Internal services


Security isolation among hosts

Security isolation at the network layer


The cost is low at the initial stage and gets higher with the growth of service volume.

The initial cost is high. As the service volume increases, the average cost becomes low.


Rarely customized

Flexibly customized and can be integrated with legacy systems

Technical architecture

Self-developed architecture, focusing on distributed and large clusters

Open-source architecture, focusing on high availability and flexibility


Services are modified based on public cloud requirements.

Proactive compatibility with and adaptation to the organization's services


O&M is performed by public cloud service providers in a unified manner.

O&M is performed by the organization or a third party.

Public Cloud Service Provider

In the global market, leading public cloud vendors are basically fixed, the market concentration rate keeps increasing, and the oligopoly competition situation is obvious. Amazon has occupied the world's largest public cloud market share since it launched the AWS cloud service in 2006. But Microsoft Azure, Google, and Alibaba Cloud, as the strongest competitors, have grown rapidly in recent years.

Alibaba Cloud occupies the largest public cloud market share in China. Other major Chinese providers include Tencent Cloud, HUAWEI CLOUD, and China Telecom e-Surfing Cloud.

About This Topic
  • Author: Gao Yangyang
  • Updated on: 2021-11-23
  • Views: 2551
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