🏢Availability Set

🔹 Core Concept
An Availability Set in Azure ensures high availability for your virtual machines by distributing them across multiple fault domains (FDs) and update domains (UDs) to minimize downtime during hardware failures or maintenance.

🔹 Purpose
Designed to protect applications from single points of failure by separating VM instances across different physical servers, storage units, and network switches.

🔹 Fault Domains (FDs)
Group of physical hardware that share a common power source and network switch.
Placing VMs in different fault domains ensures they are not affected by a single hardware failure.

🔹 Update Domains (UDs)
Represent groups of VMs that can be updated or rebooted together during planned maintenance.
Azure ensures that at least one instance remains operational during updates.

🔹 High Availability Architecture
Improves uptime by ensuring at least one VM instance in an availability set remains available during outages or system updates — achieving up to 99.95% SLA.

🔹 Automatic Distribution
When multiple VMs are deployed within an availability set, Azure automatically distributes them across FDs and UDs.

🔹 Integration with Load Balancer
Works seamlessly with Azure Load Balancer to distribute incoming traffic across VM instances for enhanced performance and reliability.

🔹 Cost Efficiency
No additional charge for creating availability sets — you only pay for the underlying virtual machines and resources used.

🔹 Best Practice for Redundancy
Recommended for multi-tier applications (e.g., web, app, database) to ensure redundancy and fault tolerance across critical components.

🔹 Monitoring & Management
Availability health can be monitored using Azure Monitor, Service Health, and Activity Logs to track uptime and maintenance events.