Virtual Machine Scale Sets

Azure Virtual Machine Scale Sets (VMSS) let you create and manage a group of identical, load-balanced VMs. They automatically increase or decrease the number of VM instances in response to demand or a defined schedule, providing high availability and application resiliency.

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What is a Virtual Machine Scale Set?

A VMSS is a collection of VMs that are:

• Identical — all created from the same base image and configuration
• Load-balanced — traffic is distributed evenly across instances
• Auto-scaling — instances are added or removed based on demand
• Zone-aware — can span Availability Zones for high availability

Key Benefits

Benefit	Description
Automatic scaling	Scale from 0 to 1,000 instances based on metrics or schedules
High availability	Distribute across fault domains and Availability Zones
Consistency	All VMs are identical — same image, size, and configuration
Integration	Works with Azure Load Balancer and Application Gateway
Cost efficiency	Scale in during low demand to reduce costs

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Orchestration Modes

VMSS supports two orchestration modes:

Uniform Orchestration