Cloud Computing

History of Cloud Computing

First Age (1970s)
- Shift from centralized to decentralized network design.
- Processing closer to users (thin to thick clients).
- Emergence of tightly coupled applications.
Second Age (1980s)
- Rise of Internet improving user connectivity.
- Increased compute load closer to users.
- Transition to independent competing companies leading to faster innovation and lower costs.
Third Age (1990s)
- Explosion of data with mobility and wireless connectivity.
- Rebirth of thin clients (browsers) with server-side computing.
- Introduction of virtualization for improved resource utilization.
Present Times (2000s)
- Adoption of loosely coupled applications benefiting from scalable infrastructure.
- Innovations in billing and user access to fractional server resources.
- Shift towards data-centric security.

Value Delivery
- Key market sectors: Software, Infrastructure, and flexibility in environment.
- Significant reduction in software costs and application development platforms.

Model for ubiquitous, on-demand network access to a shared pool of computing resources.
- Composed of five essential characteristics, three service models, and four deployment models.

On-demand self-service: Consumers manage their own services without provider assistance.
Broad network access: Accessibility across diverse client platforms.
Resource pooling: Dynamic allocation to serve multiple consumers.
Rapid elasticity: Resources can scale quickly to match demand.
Measured service: Monitoring and reporting on resource consumption.

Infrastructure-as-a-Service (IaaS): Users manage software, not infrastructure.
Software-as-a-Service (SaaS): Centralized applications for users without access to underlying infrastructure.
Platform-as-a-Service (PaaS): Integrates IaaS and SaaS capabilities for development.

Public Cloud: General public access with pay-as-you-go models.
Private Cloud: Single-tenant clouds for more control.
Hybrid Cloud: Combination of public and private, maximizing resource utilization.
Community Cloud: Shared infrastructure for specific community users with common concerns.

Rehost (lift-and-shift): Quick migration with minimal changes, often reverting to existing limitations.
Refactor: Significant modifications for cloud advantages, often restructuring applications.
Replatform: Intermediate adjustments to facilitate cloud integration.
Retire/Replace: Decommissioning applications when more effective solutions are available.