Add Availability Set to VMSS Flex migration cmdlets

[Copilot]

Description

Implements 5 new cmdlets for Availability Set to Virtual Machine Scale Set (VMSS) Flex migration as outlined in the design review issue.

New Cmdlets:

• Convert-AzAvailabilitySet - Creates new VMSS Flex and migrates all VMs (no downtime)
• Start-AzAvailabilitySetMigration - Initiates migration to existing VMSS Flex
• Test-AzAvailabilitySetMigration - Validates VMs can be migrated
• Stop-AzAvailabilitySetMigration - Cancels in-progress migration
• Move-AzVirtualMachineToVmss - Migrates individual VM with optional zone/fault domain/size targeting

Cmdlet names follow PowerShell conventions per reviewer feedback (e.g., Migrate- → Move-, Cancel- → Stop-, Validate- → Test-).

Usage Example:

# Option 1: One-step conversion (no downtime)
Convert-AzAvailabilitySet -ResourceGroupName "MyRG" -Name "MyAvSet" -VirtualMachineScaleSetName "MyVMSS"

# Option 2: Multi-step migration with VM-level control
Test-AzAvailabilitySetMigration -ResourceGroupName "MyRG" -Name "MyAvSet" -VirtualMachineScaleSetFlexibleId $vmssId
Start-AzAvailabilitySetMigration -ResourceGroupName "MyRG" -Name "MyAvSet" -VirtualMachineScaleSetFlexibleId $vmssId
Move-AzVirtualMachineToVmss -ResourceGroupName "MyRG" -Name "VM1" -TargetZone "1" -TargetFaultDomain 0

Requires subscription feature flag: Microsoft.Compute/MigrateToVmssFlex

Mandatory Checklist

• Please choose the target release of Azure PowerShell. (⚠️Target release is a different concept from API readiness. Please click below links for details.)

  • General release
  • Public preview
  • Private preview
  • Engineering build
  • No need for a release

• Check this box to confirm: I have read the Submitting Changes section of CONTRIBUTING.md and reviewed the following information:

• SHOULD update ChangeLog.md file(s) appropriately
  • Update src/{{SERVICE}}/{{SERVICE}}/ChangeLog.md.
    • A snippet outlining the change(s) made in the PR should be written under the ## Upcoming Release header in the past tense.
  • Should not change ChangeLog.md if no new release is required, such as fixing test case only.
• SHOULD regenerate markdown help files if there is cmdlet API change. Instruction
• SHOULD have proper test coverage for changes in pull request.
• SHOULD NOT adjust version of module manually in pull request

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• 1n8vsblobprodwus2184.vsblob.vsassets.io
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• 40vvsblobprodwus2135.vsblob.vsassets.io
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• wlnvsblobprodwus2188.vsblob.vsassets.io
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• wztvsblobprodwus2155.vsblob.vsassets.io
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• x0dvsblobprodwus2111.vsblob.vsassets.io
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• y5lvsblobprodwus2179.vsblob.vsassets.io
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• yf8vsblobprodwus212.vsblob.vsassets.io
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• zt8vsblobprodwus2176.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet dotnet build src/Compute/Compute/Compute.csproj (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Compute- Migration</issue_title>
<issue_description>

Guidelines

The purpose of the Azure PowerShell design review is to ensure that the cmdlets follow the same pattern across the Azure modules. An early design review reduces the risk of unnecessary implementation changes caused by a cmdlet syntax design change.

Please ensure your cmdlets comply with the design guidelines outlined in the PowerShell Design Guidelines document.

Please generate cmdlets syntax using GenerateCmdletDesignMarkdown.ps1 for review if your cmdlet is generated from API spec directly by Autorest.PowerShell.

If you just add parameter to existing cmdlets and parameter definition complies with guideline, the design review is not expected.

• Have you read above statement?

  • Yes

Service Release Details

• Is this an Embargoed Preview, A Public Preview, or a General Release?

  • Public Preview`

• What is the expected service release date?

  • 08/15/2025

• Which Powershell module are these changes being made in?

  • Az.Compute

Contact Information

• Main developer contacts (emails + github aliases)

  • soshekar

• PM contact (email + github alias)

  • mimckitt

• Other people who should attend a design review (email)

  • srcharug

High Level Scenarios

• Describe how your feature is intended to be used by customers.

  • `These APIs provide 2 ways for the user to migrate an Availability Set to a VMSS.

  • Option 1 : AvailabilitySet.ConvertToVirtualMachineScaleSet`

  • Option 2: This option requires triggering multiple commands to move each VM individually.
    AvailabilitySet.ValidateMigrationToVirtualMachineScaleSet
    AvailabilitySet.StartMigrationToVirtualMachineScaleSet

     foreach ( vm in AvailabilitySet.VMs)
        VirtualMachine.MigrateToVirtualMachineScaleSet
    

'

• Piping scenarios / how these cmdlets are used with existing cmdlets

  • { SCENARIOS OUTLINED HERE }

• Sample of end-to-end usage

  • Please provide comprehensive examples that don't assume additional setup. It helps the audience understand your feature.

  • ` Example to Convert an Availability Set to Vmss :

  • Convert-AzAvailabilitySet ` [-ResourceGroupName] "MyResourceGroup" [-Name] "MyAvailabilitySet" [-VirtualMachineScaleSetName] "MyScaleSet"

  -Example to Migrate an Availability Set with 2 VMs to a VMSS Flex

  • Start-AzAvailabilitySetMigration [-ResourceGroupName] "MyResourceGroup" [-Name] "MyAvailabilitySet" [-VirtualMachineScaleSetFlexibleId] "/subscriptions//resourceGroups/MyResourceGroup/providers/Microsoft.Compute/virtualMachineScaleSets/MyFlexibleVMSS"

  • Migrate-AzVM [-ResourceGroupName] "MyResourceGroup" [-Name] "VM1" [-TargetZone] "1" [-TargetFaultDomain] 0 [-TargetVMSize] "Standard_DS2_v2"

Syntax changes

Indicate if you are requesting an edit to existing cmdlets, adding new cmdlets, or both. Then edit the corresponding section below.

- 'New'

New Cmdlet

List the new cmdlet names.

- Convert-AZAvailabilitySet
- Validate-AZAvailabilitySetMigration
- Start-AZAvailabilitySetMigration
- Cancel-AZAvailabilitySetMigration
- Migrate-AZVirtualMachine

List the parameters for the new cmdlet(s) and the parameter types.

- Convert-AZAvailabilitySet --virtualMachineScaleSetName
- Validate-AZAvailabilitySetMigration --virtualMachineScaleSetFlexibleId
- Start-AZAvailabilitySetMigration --virtualMachineScaleSetFlexibleId
- Cancel-AZAvailabilitySetMigration
- Migrate-AZVirtualMachine --targetZone --targetFaultDomain --targetVMSize

Please describe the business logic of the cmdlet and parameters here.

- { Cmdlet and parameter business logic }

Link to cmdlet help markdown file generated by platyPS or sample syntax. The below is an example.:

PS C:\> Get-AzureRmWidget [[-ResourceGroupName] <resourceGroupName>] [[-Name] <name>] [-Detail]
 
ResourceGroup | WidgetName |
--------------|------------|
 rg1          |  widget1   |

Specific test cases

Please provide a link to the API tests that exist for this feature.

• { ENTER LINK HERE }

Additional information

• Link to the OpenAPI (swagger) spec

  • { LINK HERE }

• Link to any other Github work related to this request

  • { LINK HERE }

• Indicate any...

Custom agent used: Compute PowerShell Pull Request Agent
Specialized agent for creating PowerShell pull requests based on a design request

• Fixes Azure/azure-powershell-cmdlet-review-pr#1504

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