AZ - 900 Short Notes
Module 1
Episode 01: Cloud Computing, High Availability, Scalability, Elasticity, Agility, Fault Tolerance, and Disaster Recovery 🔗
Define cloud computing
Cloud computing is the delivery of services over the internet, including:
💻 Compute (e.g., Windows/Linux VMs, containers)
📦 Storage (e.g., files, databases)
🌐 Networking (e.g., connecting internal resources or hybrid environments)
📊 Analytics (e.g., performance monitoring, telemetry)
These services are designed to be scalable, agile, and resilient, fulfilling key characteristics that define cloud computing. Below is a summary of these critical concepts:
🔑 Key Concepts in Cloud Computing
| Term | Definition |
| Scalability | The system's ability to increase or decrease resources as needed. Includes: |
| 🔹 Vertical scaling (scale up/down) | |
| 🔹 Horizontal scaling (scale out/in) | |
| Elasticity | The system's ability to scale dynamically based on workload demand. Often powered by auto-scaling mechanisms. |
| Agility | The ability to respond quickly to change — provisioning resources within minutes instead of days/weeks. |
| Fault Tolerance | The system’s ability to remain operational despite hardware or service failures. Resources automatically shift to healthy instances. |
| Disaster Recovery | The system’s ability to recover from region-wide or service-wide outages by maintaining replicated environments in different regions. |
| High Availability | A measure of system uptime versus total time, often guaranteed by Azure SLAs. |
📌 Example: 99.9% uptime allows for ~8.76 hours downtime per year.
Azure VM Availability/Azure Virtual Machine SLA
| Deployment Scenario | Disk Type | VM Connectivity SLA |
| 2+ VM instances across 2+ Availability Zones (same region) | Any | 99.99% |
| 2+ VM instances in same Availability Set or Dedicated Host Group | Any | 99.95% |
| Single instance VM | Premium SSD or Ultra Disk | 99.9% |
| Single instance VM | Standard SSD Managed Disks | 99.5% |
| Single instance VM | Standard HDD Managed Disks | 95% |