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Azure Fundamentals · Lesson

Availability Sets and Availability Zones

Deploy VMs into an availability set or across availability zones, and understand the fault and update domain model that prevents simultaneous failures.

Why Redundancy Matters for VMs

A single Azure Virtual Machine is vulnerable to hardware failures, OS updates, and planned maintenance events. Azure provides two mechanisms to protect VM workloads from these disruptions: Availability Sets and Availability Zones. Understanding the difference between them — and when to use each — is essential for designing reliable Azure VM architectures.

What Is an Availability Set?

An Availability Set is a logical grouping of VMs within a single Azure data centre. When you place VMs in an availability set, Azure distributes them across multiple fault domains (separate power and network racks) and update domains (groups that are rebooted one at a time during maintenance). This protects against both hardware failures and planned reboots.

# Create an availability set:
az vm availability-set create \
  --resource-group myRG \
  --name myAvailabilitySet \
  --platform-fault-domain-count 2 \
  --platform-update-domain-count 5

All lessons in this course

  1. Azure SLAs and Composite SLAs
  2. Availability Sets and Availability Zones
  3. Multi-Region Active-Active Architecture
  4. Health Probes and Graceful Degradation
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