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Azure Fault and Update Domains

Azure Fault and Update Domains are features of Azure Availability Sets that help ensure high availability and reliability for virtual machines (VMs). Fault domains provide physical separation of VMs across hardware to protect against hardware failures. Update domains provide logical separation to ensure VMs are not all updated or rebooted at the same time.

Use Case: High Availability for Critical Applications

Scenario

A company needs high availability and reliability for critical applications running on Azure VMs. Azure Fault and Update Domains distribute VMs across physical and logical groups to minimize downtime.

Implementation

  1. Availability Set Creation: Create an Availability Set in the Azure portal to group VMs and distribute them across fault and update domains.
  2. Fault Domains: Physical separation of VMs across hardware (e.g., different racks). Protects against hardware failures. Up to 3 fault domains per Availability Set.
  3. Update Domains: Logical separation to prevent all VMs from being updated or rebooted simultaneously during maintenance. Up to 20 update domains per Availability Set.
  4. VM Deployment: Deploy VMs within the Availability Set. Azure automatically assigns fault and update domains for high availability.
  5. Monitoring and Management: Use Azure Monitor to track VM performance and health. Set up alerts for proactive management.

Well-Architected Framework Considerations

  • Cost Optimization: Included at no extra cost with Availability Sets. Pay only for VMs.
  • Operational Excellence: Automated distribution reduces manual intervention.
  • Performance Efficiency: Minimizes impact of hardware failures and maintenance.
  • Reliability: High availability and fault tolerance by distributing VMs.
  • Security: Role-based access control (RBAC) and integration with Azure Active Directory (AAD).

References