AZ-900 Cloud Concepts - Types of cloud models-4
Published: 2020-11-09 12:53:59

Highlights from the below link
https://docs.microsoft.com/en-us/learn/modules/distinguish-types-cloud-models/

There are three different cloud deployment models:
**Public Cloud, Private Cloud, and Hybrid Cloud**.

A cloud deployment model defines where your data is stored and how your customers interact with it – how do they get to it, and where do the applications run? It also depends on how much of your own infrastructure you want or need to manage.

**Public cloud**
  * A public cloud is owned by the cloud services provider. It provides resources and services to multiple organizations and users, who connect to the cloud service via a secure network connection, typically over the internet.
  * Public cloud models have the following characteristics:
    * **Ownership** - Resources are owned and operated by cloud service providers.
    * **Multiple end users** - Public cloud modes may make their resources available to multiple organizations.
    * **Public access** - Public access allows the public to access the desired cloud services.
    * **Availability** - Public cloud is the most common cloud-type deployment model.
    * **Connectivity** - Users and organizations are typically connected to the public cloud over the internet using a web browser.
    * **Skills** - Public clouds do not require deep technical knowledge to set up and use its resources.

  * **Advantages**:
    * **No CapEx**. You don’t have to buy a new server in order to scale.
    * **Agility**. Applications can be made accessible quickly and de-provisioned whenever needed.
    * **Consumption-based model**. Organizations pay only for what they use and operate under an OpEx model.
    * **Maintenance**. Organizations have no responsibility for hardware maintenance or updates.
    * **Skills**. No deep technical skills are required to deploy, use, and gain the benefits of a public cloud. Organizations can leverage the skills and expertise of the cloud provider to ensure workloads are secure, safe, and highly available.

  * **Disadvantages**:

    * **Security**. There may be specific security requirements that cannot be met by using public cloud.
    * **Compliance**. There may be government policies, industry standards, or legal requirements which public clouds cannot meet.
    * **Ownership**. Organizations don't own the hardware or services and cannot manage them as they may wish.
    * **Specific scenarios**. If organizations have a unique business requirement, such as having to maintain a legacy application, it may be hard to meet that requirement with public cloud services.

**Private cloud**
  *  A private cloud is owned and operated by the organization. They have their own datacenter and provide self-service access to compute resources to users within their organization. 

  * Private cloud models have the following characteristics:

    * **Ownership**. The owner and user of the cloud services are the same.

    * **Hardware**. The owner is entirely responsible for the purchase, maintenance, and management of the cloud hardware.
    * **Users**. A private cloud operates only within one organization and cloud computing resources are used exclusively by a single business or organization.
   * **Connectivity**. A connection to a private cloud is typically made over a private network that is highly secure.
   * **Public access**. Does not provide access to the public.
   * **Skills**. Requires deep technical knowledge to set up, manage, and maintain.
 * Use cases: Store Organization Sensitive data, Govt Data etc.

  * **Advantages**:
   * **Control**. Organizations have complete control over the resources.
   * **Security**. Organizations have complete control over security.
   * **Compliance**. If organizations have very strict security,  compliance, or legal requirements, a private cloud may be the only viable option.
   * **Specific scenarios. If an organization has a specific scenario not easily supported by a public cloud provider (such as having to maintain a legacy application), it may be preferable to run the application locally.

  * **Disadvantages**:

   * **Upfront CapEx**. Hardware must be purchased for start-up and maintenance.
   * **Agility**. Private clouds are not as agile as public clouds, because you need to purchase and set up all the underlying infrastructure before they can be leveraged.
   * **Maintenance**. Organizations have the responsibility for hardware maintenance and updates.
   * **Skills**. Private clouds require in-house IT skills and expertise that may be hard to get or be costly.

**Hybrid cloud**
 * A hybrid cloud combines both public and private clouds, allowing you to run your applications in the most appropriate location.

 * Hybrid cloud models have the following characteristics:

  * **Resource location**. Specific resources run or are used in a public cloud, and others run or are used in a private cloud.
  * **Cost and efficiency**. Hybrid cloud models allow an organization to leverage some of the benefits of cost, efficiency, and scale that are available with a public cloud model.
  * **Control**. Organizations retain management control in private clouds.
  * **Skills**. Technical skills are still required to maintain the private cloud and ensure both cloud models can operate together.

 * **Advantages**:
   * **Flexibility**. The most flexible scenario: with a hybrid cloud setup, an organization can decide to run their applications either in a private cloud or in a public cloud.
   * **Costs**. Organizations can take advantage of economies of scale from public cloud providers for services and resources as they wish. This allows them to access cheaper storage than they can provide themselves.
   * **Control**. Organizations can still access resources over which they have total control.
   * **Security**. Organizations can still access resources for which they are responsible for security.
   * **Compliance**. Organizations maintain the ability to comply with strict security, compliance, or legal requirements as needed.
   * **Specific scenarios**. Organizations maintain the ability to support specific scenarios not easily supported by a public cloud provider, such as running legacy applications.

 * **Disadvantages**:
   * **Upfront CapEx**. Upfront CapEx is still required before organizations can leverage a private cloud.
   * **Costs**. Purchasing and maintaining a private cloud to use alongside the public cloud can be more expensive than selecting a single deployment model.
   * **Skills**. Deep technical skills are still required to be able to set up a private cloud.
   * **Ease of management**. Organizations need to ensure there are clear guidelines to avoid confusion, complications, or misuse.