Following is an excerpt from Cloud Computing Chapter from book Azure Study & Lab Guide For Beginners.
Before going into Cloud Computing let’s discuss about Server Virtualization. Server Virtualization is the base on which Cloud Computing is built.
With Server Virtualization a hypervisor installed on compute host creates and runs Virtual Machines. Each Virtual Machine runs a unique guest operating system. VMs with different operating systems can run on the same physical server – a Windows VM can sit alongside a Linux VM.
Example of Hypervisor includes VMware ESXi, Microsoft Hyper-v, Citrix XenServer and Linux KVM.
Figure below shows architecture of Server Virtualization.
When you request a Compute instance in Public Cloud, you don’t get access to full Physical Server. Instead Automation and Orchestration technologies work in backend to create a Virtual Machine for you on a Physical Server. In Cloud this Physical Server will also host Virtual Machines for different customers.
Cloud Computing is on-demand availability of resources such as Compute, Data Storage, Databases etc over the internet.
Cloud Computing uses Virtualization, Automation and Orchestration technologies to enable end users to use Self-service option to provision resources and deploy workloads without direct intervention from the Cloud Provider’s IT staff.
With Cloud Computing, Companies rent Cloud Providers equipment using pay per use model. This reduces capital expenditure for the Companies. Cloud Providers share their equipment with Multiple Companies which allows them to price their services competitively.
Pay per use: In Pay per use model Users pay only for the time they have used the Cloud Resources.
Self-service provisioning: WithSelf-service option users provision compute and other resources in cloud without direct intervention from the Cloud Provider’s IT staff. Secondly Companies don’t require trained IT Administrators to provision cloud resources.
Scalability: You can Scale-up or Scale-down compute resources on-demand. You can Scale-up compute resources using Scale-out or Scale-up option. With Scale-out you add additional Compute Resources (Virtual Machines) to service your application. With Scale-up you use Virtual Machine with additional and more Powerful Resources.
Scale-down feature helps in minimizing the cost of the compute resources in cloud.
Whereas in on-premises environment you provision compute resources as per peak requirements of the application. Peak requirement usually happens during particular time of the day or particular day in a month.
Multi-tenancy: In Public Cloud multiple customers access the same physical infrastructure. Multi-tenancy allows customers to access the same physical infrastructures and applications but they still retain privacy and security over their own data.
Cost Savings: Using cloud computing organizations reduce capital costs (Capital Expenditure or Capex) as organizations don’t have to spend large amounts of money buying IT equipments and maintaining large Data Centers. Instead they pay monthly rent (Operation Expenditure or Opex) for the cloud resources they have used.
High Availability and Disaster Recovery: Organizations want their Applications to be available 100% of time to avoid any Business disruption because of Application downtime. Setting up High Availability and Disaster Recovery in on-premises environment is a very expensive and time consuming process.
Public Cloud offers many features which allow you to set up High Availability and Disaster Recovery at nominal cost and in quick time.
Using Public Cloud you can use features such as Multiple Availability Zones and Regions, Replication of Storage and Database Services within and across regions, Regional and Global Load Balancers etc to set up High Availability and Disaster Recovery quickly and at reasonable cost.
Managed Services: Managed Services is one of the main reason that organizations are moving to Cloud. Managed Services such as Database, Analytics, Big Data, Machine learning, Storage, Identity and Security does not require skilled manpower for deployment. Additional features of Managed Services such as Backup and High Availability can be configured without requiring any expertise. Managed Services can be deployed within seconds to minutes. Additionally you don’t have to patch, update and upgrade Managed Services. Azure automatically patches, updates and upgrades Managed Services for you.
Cloud Services can be delivered in multiple ways such as IaaS, PaaS and SaaS.
The Diagram below shows the difference between IaaS, PaaS and SaaS. The boxes with Dark grey background are managed by Cloud Provider.
Infrastructure-as-a-Service (IaaS): IaaS refers to the Virtual Server or Virtual Machine or Compute instance offered by a Cloud Provider. End Users Install Operating System and Applications on the Compute instance. Operating System image is provided by Cloud Provider. Cloud Provider offer Multiple SKU’s of Compute instance which differs in terms of CPU, Memory and Storage configurations. Examples of IaaS include AWS EC2 instance, Azure Virtual Machine and Google Compute Engine.
Platform-as-a-Service (PaaS): In PaaS model Cloud Provider delivers hardware, operating systems and Software runtime tools such as ASP.NET, PHP, Java, Node.JS, Python, Ruby etc to end users as a service. Examples of PaaS include Azure Web App, Google App Engine and AWS Elastic Beanstalk.
Software-as-a-Service (SaaS): In SaaS model Cloud Provider delivers Software Applications or Web Applications over the internet. Examples of SaaS include Salesforce CRM, Netsuite ERP and Yahoo Mail.
Public Cloud: In this Model Cloud Provider delivers Compute, Storage and other Cloud Services over the internet. Public Cloud uses shared infrastructure that is shared between all consumers of the public cloud. Public Cloud provides multiple benefits such as Pay per use, Scalability, Managed Services and Cost savings. Examples of Public Cloud Providers include Amazon Web Services, Google Cloud Platform and Microsoft Azure.
Private Cloud: In this Model Cloud Services are delivered through Organization owned Data Center to internal users. Private Cloudmodel is a Single-tenant architecture. It uses on-premises hardware and provides direct control of underlying Cloud Infrastructure. Example of Private Cloud Technologies include Openstack, Apache Cloudstack, Vmware vRealize Automation and Vmware vCloud Director.
Hybrid Cloud: Hybrid Cloud Model is a mix of on-premises infrastructure, Private Cloud and Public Cloud. In this model workloads are running in both on-premises and Public Cloud. In this Model you have multiple scenarios for running workloads. You can have Applications running in Public Cloud and they are accessing Database on-premises. You can have legacy workloads running on-premises and all other workloads running in cloud. You can have mission critical workloads running on-premises because of regulatory compliance reasons and balance workloads running in cloud.
Following are some of the Public Cloud Providers who offer Public Cloud Computing.
- Amazon Web Services (AWS)
- Google Cloud Platform (GCP)
- Microsoft Azure
- Oracle Cloud Infrastructure (OCI)
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