Resize an Azure Virtual Machine

Lab Overview

After you create an Azure virtual machine, you can scale the VM up or down by changing the VM size. In some cases, you must deallocate the VM first. This can happen if the new size is not available on the hardware cluster that is currently hosting the VM.

If the virtual machine is currently running, changing its size will cause it to be restarted. Stopping the virtual machine may reveal additional sizes, as well.

Learning Objectives

In this Azure simulation, you will resize a running virtual machine. The virtual machine will automatically restart as part of the process.

Exam Relevance

The skills you learn in this lab are necessary to pass the following Azure certification exams:

AZ-104
AZ-303
AZ-304

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Azure VM Scale Sets — Quick Reference

Fast lookup for orchestration modes, autoscaling, load balancing, updates & CLI.

Core Benefits

Create & manage groups of identical or heterogeneous VMs.
Automatic scaling based on demand or schedule.
Load balance traffic across instances.
HA across fault domains & availability zones.
Pay only for VMs; no charge for scale set itself.

Scale sets can handle up to 1,000 VMs (Marketplace/Gallery images).

Orchestration Modes

Mode	Profile	Best For
Flexible	Standard Azure VMs	New workloads (default)
Uniform	Identical VMs	Legacy large-scale workloads

Flexible: Full standard VM APIs, dynamic mixing (Spot+on-demand), 1,000 VMs. Uniform: Locked after creation; up to 1,000 VMs (Marketplace) or 600 (custom images).

Orchestration Comparison

Feature	Flexible	Uniform
Standard VM APIs	Yes	No
Mix instance types	Yes	No
RBAC per VM	Yes	No
Azure Backup	Yes	No
Site Recovery	Yes	No
Fault domains	1–3	1–5

Autoscaling Metrics

Host metrics: CPU, memory, disk (no agent needed).
Guest metrics: Custom counters (Azure Diagnostics Extension).
App Insights: Application-level performance metrics.
Rules: Min/max capacity, scale-out/in thresholds, cooldown periods.

Autoscale rules use metrics from Load Balancer, Diagnostics, or App Insights.

Load Balancing

Type	Layer	Best For
Internal LB	L4	Backend pools
Public LB	L4	External traffic
App Gateway	L7	HTTP/HTTPS + WAF

Large scale sets (>100 VMs) require Load Balancer Standard SKU.

Availability & Zones

Single zone: All VMs in one availability zone.
Zone-redundant: VMs spread across 1, 2, or 3 zones in region.
Zone balance: Auto-spread VMs evenly across zones (±1 VM).
Fault domains: 1–3 per zone for best-effort resilience.

Use availability zones for datacenter-level failure protection.

Upgrade Policies (Uniform)

Policy	Rollout	Use
Automatic	Batch	App can tolerate disruption
Rolling	Controlled	Gradual, managed updates
Manual	On-demand	Full control; explicit API calls

Flexible mode uses standard VM updates; no built-in rolling.

Application Deployment

Custom image: Preinstall app; faster provisioning.
Custom Script Extension: Download & run scripts post-deploy.
Azure VM Applications: Package & manage centrally (new).
PowerShell DSC: Desired State Configuration for consistency.

Custom images: 600 VMs max; Marketplace images: 1,000 VMs.

Planned Maintenance & Health

Azure Patch Manager: Automated guest OS patching.
Application Health Extension: Monitor app heartbeat; auto-replace unhealthy.
Health probes (Uniform): Monitor via load balancer.
Platform updates coordinated; typically brief interruption.