1. Traditional Deployment

• Overview: Applications ran on physical servers without resource boundaries, leading to allocation issues.
• Challenges:
  • Resource competition: One application could dominate resources, causing others to underperform.
  • Scaling issues: Running each app on a separate server was resource-intensive and costly.
• Solution: Virtualization and containerization emerged to address these limitations.

2. Virtualization

• Definition: Creation of virtual versions of OS, servers, storage, or network resources using software to simulate hardware.
• Benefits:
  • Run multiple OS and apps on a single server.
  • Improves resource utilization and scalability.
• Types:
  • Network Virtualization: Divides network bandwidth into secure, assignable channels for improved speed, availability, and security.
  • Storage Virtualization: Pools multiple storage devices into a single, centrally managed virtual device (e.g., in SANs).
    • Benefits: Remote storage appears local, high availability, improved performance.
  • Data Virtualization: Aggregates data from multiple sources into a single logical view without needing to know storage locations.
    • Benefits: Abstracts technical details, enables data federation, single access point.
  • Desktop Virtualization: Isolates desktop OS, allowing remote access (e.g., shared hosted desktops via Microsoft Remote Desktop Services).
  • Application Virtualization: Runs apps separately from the accessing device, simplifying updates and patching.
  • Hardware Virtualization: Creates virtual machines (VMs) that act like real computers with their own OS.
    • Type 1 (Bare Metal) Hypervisor: Runs directly on hardware (e.g., VMware ESXi).

3. Microservices Architecture

• Definition: Architectural method using independently deployable services with their own logic and database.
• Characteristics:
  • Each service focuses on a specific goal.
  • Decouples business concerns into independent code bases.
  • Aligns with DevOps for continuous delivery.
• Pros:
  • Agility: Small teams deploy frequently.
  • Flexible scaling: Add instances to handle load.
  • Continuous deployment: Frequent, faster releases (e.g., 2-3 times/day).
  • Maintainable/testable: Easy to update, isolate, and fix issues.
  • Independent deployment: Deploy features without affecting others.
  • Technology flexibility: Teams choose their tools.
  • High reliability: Service failures don’t crash the entire app.
• Cons:
  • Development sprawl: Increased complexity from multiple services.
  • Infrastructure costs: Each service requires its own testing, hosting, and monitoring.
  • Organizational overhead: More coordination needed.
  • Debugging challenges: Distributed logs and processes complicate troubleshooting.
  • Lack of standardization: Diverse languages and logging standards.
  • Unclear ownership: Hard to track services and support contacts.

4. Containerization

• Definition: Packaging software code with OS libraries and dependencies into a lightweight, portable executable (container).
• Comparison with VMs:
  • VMs: Hardware-level virtualization, heavyweight, slow provisioning, fully isolated, separate OS per VM, boots in minutes.
  • Containers: OS-level virtualization, lightweight, fast provisioning, process-level isolation, share OS, boots in seconds.
• Benefits:
  • Portability: Runs consistently across platforms/clouds.
  • Agility: Supports DevOps with tools like Docker Engine.
  • Speed: Lightweight, no OS boot time, faster start-up.
  • Fault Isolation: One container’s failure doesn’t affect others.
  • Efficiency: Shares OS kernel, smaller size, runs more containers per server.
  • Ease of Management: Orchestration platforms (e.g., Kubernetes) automate scaling, updates, and monitoring.
  • Security: Isolates apps, uses OS security (e.g., SELinux) to prevent malicious code spread.

5. Docker

• Definition: Open-source platform for building, deploying, and managing containers.
• Why Docker?:
  • Simplifies creating deployable app packages.
  • Ensures consistent environments (on-prem or cloud).
  • Lightweight compared to VMs.