Cloud Architecture Models

There are four types of cloud models

Private Cloud:

• When the data centers are built and maintained by the organization
• A private cloud can be physically located at your company's premises or it can be hosted by the third-party service provider at any other location.
• Private cloud is maintained by the company IT Department.
• The organization has full control over the hardware, software, and licenses.
• Your organization is fully responsible for the maintenance and up-gradation of the data center and resources within the data center
• In the private cloud architecture model, data stays within the company data center providing maximum security of the company information.
• This type of model is used when security is the prime concern like government application, organization's financial data, or any other business-critical solutions.

Advantages of Private Cloud

• Flexibility: The organization can customize its infrastructure as per the specific requirement of its projects. this provides flexibility in setting up the data center.
• Security and Control: Infrastructure is owned by the company itself, which provides greater security and maximum control over the infrastructure.
• Scalability: Private cloud provides greater scalability in terms of hardware and software installation. According to every organization's requirement, they(Hardware and Software) can be scaled up and scale down quickly and in a secure way

Disadvantages of private cloud

• Cost: Creating and managing a company's own infrastructure for hardware and software resources can be costly.
• Skilled Resources: Organizations need to always keep a team of skilled resources who can manage the Infrastructure. Maintaining infrastructure also needs 24*7 support demanding high availability of skilled resources and a lot of monetary investments.
• Limit on Scalability: Every application has different types of requirements about hardware and software. It may not be always possible to scale up or scale down the infrastructure within the company's space limits and budget.
• Limited area of Operations: Private cloud operates within an organization, so it is obvious that the area of operation is also limited to that organization.

Public Cloud:

• Nowadays, for most applications, public cloud infrastructure is a common scenario.
• The resources like VMs, storage, etc... are owned by the Cloud Service Provider and users can access them over the internet using the browser.
• In public cloud architecture, hardware and software installation, up-gradation, maintenance activities are done by cloud service providers.
• In the public cloud, you share the same Network device, storage, hardware with other companies or cloud tenants.
• All the developers across the organization, are able to access the same version of software tools avoiding any tension about the mismatch in the software versions.

Advantages of Public Cloud

• Low Cost: You pay for what you use. No upfront expenditure on heavy infrastructure setup.
• No Maintenance: All the hardware and software are maintained and managed by the cloud service provider. Also based on SLA (Service Level Agreement) with Cloud service providers, it is their responsibility to keep the hardware and software up and running.
• Scalability: For increased demand, you can scale up the resources quickly. Same way if the resources are no longer needed then you can easily scale down the resources and save money. Again, you just pay for what you use.
• Reliability: Cloud computing services come with the advantages of data backup, disaster (flood, tornado, cyber-attack) recovery, fault tolerance. That makes your business management tension-free.

Disadvantages of Public Cloud

• Security: Your application and data are going to be stored in the cloud, in the data centers which are not owned by you. Tools and Resources are also shared publicly.
• Performance: You access each component using the internet. Now if you have low bandwidth, it may hamper your development and delivery timeline.
• Customization: Compared to the Private cloud, this model has less scope of customization.
• Access: You cannot physically access the server.
• Control: You don’t have any control over the version of the software and tools you are using.

Hybrid Cloud:

• In Hybrid Cloud, some part of your architecture is owned by the organization, and some part is owned by the Cloud Service Provider.
• For a Hybrid cloud, you need to set up a system to move the data between the Private and Public Cloud.
• Organizations choose this model because, on one hand, they want to keep some apps and data in on-premises, and on the other hand they also want to utilize some latest features and services from the cloud.
• In the Hybrid model, critical actions are performed in the Private cloud and non-critical activities are done in the Public cloud.

Advantages of Hybrid Cloud

• Security: Critical activities are performed in the Private cloud, so it is obviously more secure than Public Cloud.
• Flexibility: You can add more resources as and when needed in the public cloud, it is just a matter of synchronizing them with the Private cloud.
• Control: Organization has full control over whatever is there in a private cloud.
• Saves Capital Expenditure: For short-term projects, you don’t need to invest much in private infrastructure, rather you can invest in the cloud for a period of time and release the resources after that.

Disadvantages of Hybrid Cloud

• Complex Infrastructure: Setting up Hybrid infrastructure is the most difficult amongst all the cloud architecture models (Public, Private, Hybrid).
• Connectivity: The synchronization between on-premises and cloud, has a very high dependency on internet connectivity.
• Compatibility: It is very critical to check the compatibility level of the resources (hardware, software, other tools) between the public cloud and the private cloud.
• Staff: You still need a lot of IT staff and in some cases may be more to handle complex hybrid architecture.

Multicloud:

1. More than 1 cloud service from more than 1 cloud service provider (Public/Private) form Multicloud.
2. All Hybrid clouds are Multiclouds but not all Multiclouds are hybrid clouds.
   1. Two or more Public (Or Private) clouds make Multiloud but it is not a Hybrid cloud. A cloud is considered Hybrid-only when there is at least 1 Public and 1 private cloud is involved.