Cloud Computing: Basics and Service Models

• Cloud computing is the on-demand availability of computer system resources, especially data storage and computing power, without direct active management by the user.
• Large clouds often have functions distributed over multiple locations, each a data center.
• Cloud computing relies on sharing of resources to achieve coherence and economies of scale.
• Advocates claim that cloud computing allows companies to avoid or minimize up-front IT infrastructure costs.
• Providers of public cloud services often use a "pay-as-you-go" model.
• Cloud computing can be divided into different service models, including Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS).

Essential Characteristics

• On-demand self-service: A consumer can unilaterally provision computing capabilities, such as server time and network storage, as needed automatically without requiring human interaction with each service provider.
• Broad network access: Capabilities are available over the network and accessed through standard mechanisms that promote use by heterogeneous thin or thick client platforms (e.g., mobile phones, tablets, laptops, and workstations).
• Resource pooling: The provider's computing resources are pooled to serve multiple consumers using a multi-tenant model, with different physical and virtual resources dynamically assigned and reassigned according to consumer demand.
• Rapid elasticity: Capabilities can be elastically provisioned and released, in some cases automatically, to scale rapidly outward and inward commensurate with demand. To the consumer, the capabilities available often appear to be unlimited and can be appropriated in any quantity at any time.
• Measured service: Cloud systems automatically control and optimize resource use by leveraging a metering capability at some level of abstraction appropriate to the type of service (e.g., storage, processing, bandwidth, and active user accounts). Resource usage can be monitored, controlled, and reported, providing transparency for both the provider and consumer of the utilized service.

Service Models

• Cloud computing service models are categorized into Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS).

Infrastructure as a Service (IaaS)

• IaaS provides consumers with the capability to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications.
• The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, deployed applications, and possibly limited control of select networking components.
• Examples: Amazon Web Services (AWS) EC2, Microsoft Azure Virtual Machines, Google Compute Engine.

Platform as a Service (PaaS)

• PaaS provides consumers with the capability to deploy onto the cloud infrastructure consumer-created or acquired applications created using programming languages, libraries, services, and tools supported by the provider.
• The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, or storage, but has control over the deployed applications and possibly configuration settings for the application-hosting environment.
• Examples: AWS Elastic Beanstalk, Google App Engine, Salesforce Heroku.

Software as a Service (SaaS)

• SaaS provides consumers with the capability to use the provider's applications running on a cloud infrastructure.
• The applications are accessible from various client devices through a thin client interface such as a web browser (e.g., web-based email) or a program interface.
• The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited user-specific application configuration settings.
• Examples: Salesforce, Google Workspace, Microsoft Office 365.

Deployment Models

• Cloud deployment models can be categorized into private, community, public, and hybrid clouds.

Private Cloud

• The cloud infrastructure is provisioned for exclusive use by a single organization comprising multiple consumers (e.g., business units).
• It may be owned, managed, and operated by the organization, a third party, or some combination of them, and it may exist on or off premises.
• Private clouds offer increased control and security for sensitive data and applications.

Community Cloud

• The cloud infrastructure is provisioned for exclusive use by a specific community of consumers from organizations that have shared concerns (e.g., mission, security requirements, policy, and compliance considerations).
• It may be owned, managed, and operated by one or more of the organizations in the community, a third party, or some combination of them, and it may exist on or off premises.
• Community clouds are suitable for organizations with similar requirements and compliance needs.

Public Cloud

• The cloud infrastructure is provisioned for open use by the general public.
• It may be owned, managed, and operated by a business, academic, or government organization, or some combination of them.
• It exists on the premises of the cloud provider.
• Public clouds offer scalability and cost-effectiveness but may have concerns regarding security and compliance.

Hybrid Cloud

• The cloud infrastructure is a composition of two or more distinct cloud infrastructures (private, community, or public) that remain unique entities, but are bound together by standardized or proprietary technology that enables data and application portability (e.g., cloud bursting for load balancing between clouds).
• Hybrid clouds offer a balance between control and flexibility, allowing organizations to leverage the benefits of both private and public clouds.

Benefits of Cloud Computing

• Cost Savings: Reduced capital expenditure (CAPEX) and operating expenses (OPEX) due to pay-as-you-go model and reduced need for on-premises infrastructure.
• Scalability: Ability to easily scale resources up or down based on demand, ensuring optimal performance and cost efficiency.
• Flexibility: Access to a wide range of services and applications that can be customized to meet specific business needs.
• Increased Collaboration: Enhanced collaboration capabilities through easy sharing and access to data and applications from anywhere.
• Disaster Recovery: Improved disaster recovery capabilities through data replication and backup in geographically diverse locations.
• Automatic Updates: Cloud providers handle software updates and maintenance, freeing up IT staff to focus on other priorities.

Concerns and Challenges

• Security: Concerns about data security and privacy in the cloud, especially for sensitive information.
• Compliance: Challenges in meeting regulatory compliance requirements, particularly for industries with strict data governance policies.
• Vendor Lock-in: Risk of being locked into a specific cloud provider, making it difficult to switch to another provider.
• Downtime: Dependence on the cloud provider's infrastructure, which can be subject to downtime and service disruptions.
• Data Portability: Challenges in migrating data and applications between different cloud environments.
• Complexity: Managing and integrating cloud services can be complex, requiring specialized skills and expertise.