[Compute] Add BestEffortAligned storage FD alignment support for VMSS Flex by Dthomas0729 · Pull Request #29575 · Azure/azure-powershell

Dthomas0729 · 2026-05-12T14:57:50Z

Adds BestEffortAligned storage Fault Domain (FD) alignment mode to VMSS Flex, plus per-disk alignment controls on both VMSS templates and individual VMs within a Flex VMSS.

Based on PR #29496 (AI-generated draft) with the following fixes:

Build fix: Added missing using Microsoft.WindowsAzure.Commands.Utilities.Common in AddAzureVMDataDiskCommand.cs (IsParameterBound was unresolvable)
Bug fix: Added ZonalPlatformFaultDomainAlignMode handling to BuildPutObject() in Update-AzVmss — the PUT path was silently dropping the property
Test improvement: Updated Test-VirtualMachineScaleSetConfigStorageFaultDomainAlignment to be end-to-end (creates VNet, VMSS, and verifies via Get-AzVmss round-trip)
Test addition: Added Test-VMStorageFaultDomainAlignment covering Set-AzVMOSDisk and Add-AzVMDataDisk with StorageFaultDomainAlignment

New Parameters

Cmdlet	Parameter	Values
`New-AzVmssConfig`	`-ZonalPlatformFaultDomainAlignMode`	Aligned, Unaligned, BestEffortAligned
`New-AzVmss` (SimpleParameterSet)	`-ZonalPlatformFaultDomainAlignMode`	same
`Update-AzVmss`	`-ZonalPlatformFaultDomainAlignMode`	same (mutable on existing VMSS)
`Set-AzVmssStorageProfile`	`-OsDiskStorageFaultDomainAlignment`	Aligned, BestEffortAligned
`Add-AzVmssDataDisk`	`-StorageFaultDomainAlignment`	Aligned, BestEffortAligned
`Set-AzVMOSDisk`	`-StorageFaultDomainAlignment`	Aligned, BestEffortAligned
`Add-AzVMDataDisk`	`-StorageFaultDomainAlignment`	Aligned, BestEffortAligned

azure-client-tools-bot-prd · 2026-05-12T14:58:14Z

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Copilot

Pull request overview

Adds BestEffortAligned storage Fault Domain alignment support for VMSS Flex at both the VMSS level (ZonalPlatformFaultDomainAlignMode) and per-disk level (StorageFaultDomainAlignment), surfacing the new properties through cmdlet parameters, models, and help.

Changes:

Added new cmdlet parameters and wiring to persist ZonalPlatformFaultDomainAlignMode for VMSS Flex create/update flows.
Added per-disk StorageFaultDomainAlignment support for VM OS/data disks and VMSS template disks.
Updated help markdown, changelog, and added new scenario tests for the new parameters.

Reviewed changes

Copilot reviewed 16 out of 21 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
src/Compute/Compute/VirtualMachine/Config/SetAzureVMOSDiskCommand.cs	Adds `-StorageFaultDomainAlignment` to `Set-AzVMOSDisk` and sets the SDK model property when bound.
src/Compute/Compute/VirtualMachine/Config/AddAzureVMDataDiskCommand.cs	Adds `-StorageFaultDomainAlignment` to `Add-AzVMDataDisk` and populates `DataDisk.StorageFaultDomainAlignment`.
src/Compute/Compute/Strategies/ComputeRp/VirtualMachineScaleSetStrategy.cs	Extends the Flex VMSS strategy builder to carry `ZonalPlatformFaultDomainAlignMode`.
src/Compute/Compute/Manual/VirtualMachineScaleSetCreateOrUpdateMethod.cs	Adds `-ZonalPlatformFaultDomainAlignMode` to `New-AzVmss` (SimpleParameterSet) and passes it into the strategy.
src/Compute/Compute/help/Update-AzVmss.md	Documents the new `-ZonalPlatformFaultDomainAlignMode` parameter.
src/Compute/Compute/help/Set-AzVmssStorageProfile.md	Documents `-OsDiskStorageFaultDomainAlignment` for VMSS template OS disk.
src/Compute/Compute/help/Set-AzVMOSDisk.md	Documents `-StorageFaultDomainAlignment` for VM OS disks.
src/Compute/Compute/help/New-AzVmssConfig.md	Documents `-ZonalPlatformFaultDomainAlignMode` for VMSS config objects.
src/Compute/Compute/help/New-AzVmss.md	Documents `-ZonalPlatformFaultDomainAlignMode` for `New-AzVmss` SimpleParameterSet.
src/Compute/Compute/help/Add-AzVmssDataDisk.md	Documents `-StorageFaultDomainAlignment` for VMSS template data disks.
src/Compute/Compute/help/Add-AzVMDataDisk.md	Documents `-StorageFaultDomainAlignment` for VM data disks.
src/Compute/Compute/Generated/VirtualMachineScaleSet/VirtualMachineScaleSetUpdateMethod.cs	Adds `ZonalPlatformFaultDomainAlignMode` handling to both PATCH and PUT object builders.
src/Compute/Compute/Generated/VirtualMachineScaleSet/Config/SetAzureRmVmssStorageProfileCommand.cs	Adds `-OsDiskStorageFaultDomainAlignment` and sets `OsDisk.StorageFaultDomainAlignment` in the VMSS config.
src/Compute/Compute/Generated/VirtualMachineScaleSet/Config/NewAzureRmVmssConfigCommand.cs	Adds `-ZonalPlatformFaultDomainAlignMode` to `New-AzVmssConfig` and sets it on the config object.
src/Compute/Compute/Generated/VirtualMachineScaleSet/Config/AddAzureRmVmssDataDiskCommand.cs	Adds `-StorageFaultDomainAlignment` and assigns it to the VMSS template data disk model.
src/Compute/Compute/Generated/Models/PSVirtualMachineScaleSet.cs	Surfaces `ZonalPlatformFaultDomainAlignMode` on the PS VMSS model for round-tripping.
src/Compute/Compute/ChangeLog.md	Adds upcoming release notes for the new alignment parameters.
src/Compute/Compute.Test/ScenarioTests/VirtualMachineTests.ps1	Adds a new scenario test function for VM OS/data disk alignment parameters.
src/Compute/Compute.Test/ScenarioTests/VirtualMachineTests.cs	Registers the new VM alignment scenario test as a check-in test.
src/Compute/Compute.Test/ScenarioTests/VirtualMachineScaleSetTests.ps1	Adds scenario tests validating VMSS-level and template-level alignment settings.
src/Compute/Compute.Test/ScenarioTests/VirtualMachineScaleSetTests.cs	Registers the new VMSS alignment scenario tests as check-in tests.

audreyttt · 2026-05-13T20:54:00Z

/azp run

azure-pipelines · 2026-05-13T20:54:20Z

Azure Pipelines successfully started running 3 pipeline(s).

audreyttt

Overall looks good, tests need to be verified and recorded

YanaXu · 2026-05-15T02:58:02Z

Hi @Dthomas0729, please fix test errors.

Copilot

Pull request overview

Copilot reviewed 16 out of 24 changed files in this pull request and generated 3 comments.

Copilot

Pull request overview

Copilot reviewed 16 out of 24 changed files in this pull request and generated 8 comments.

VeryEarly · 2026-05-15T17:39:07Z

/azp run

azure-pipelines · 2026-05-15T17:39:24Z

Azure Pipelines successfully started running 3 pipeline(s).

VeryEarly · 2026-05-18T14:39:03Z

/azp run

azure-pipelines · 2026-05-18T14:39:24Z

Azure Pipelines successfully started running 3 pipeline(s).

Dthomas0729 · 2026-05-18T15:18:38Z

@microsoft-github-policy-service agree company="Microsoft"

YanaXu · 2026-05-19T02:22:46Z

Hi, @Sandido, @grizzlytheodore, @haagha, could you please review this PR and approve it if it's ready?

audreyttt · 2026-05-19T14:36:05Z

/azp run

azure-pipelines · 2026-05-19T14:36:26Z

Azure Pipelines successfully started running 3 pipeline(s).

audreyttt · 2026-05-19T14:37:28Z

@YanaXu approved

Copilot

Pull request overview

Copilot reviewed 16 out of 24 changed files in this pull request and generated 6 comments.

Agent-Logs-Url: https://github.com/Azure/azure-powershell/sessions/3fdac09c-315d-46f9-a050-f29297b7ba37 Co-authored-by: haagha <64601174+haagha@users.noreply.github.com>

…ds for alignment support

asserting on the property being non-null/one-of('Aligned','Unaligned') instead, or using -StorageFaultDomainAlignment 'Aligned' Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

YanaXu · 2026-05-22T01:33:59Z

/azp run

azure-pipelines · 2026-05-22T01:34:15Z

Azure Pipelines successfully started running 3 pipeline(s).

audreyttt · 2026-05-22T04:16:21Z

/azp run

azure-pipelines · 2026-05-22T04:16:37Z

Azure Pipelines successfully started running 3 pipeline(s).

Copilot

Pull request overview

Copilot reviewed 16 out of 24 changed files in this pull request and generated no new comments.

Copilot AI review requested due to automatic review settings May 12, 2026 14:57

Dthomas0729 requested review from NoriZC, audreyttt, haagha, ookoka, teresaritorto and yanzhudd as code owners May 12, 2026 14:57

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Comment thread src/Compute/Compute.Test/ScenarioTests/VirtualMachineTests.ps1 Outdated

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Comment thread src/Compute/Compute/ChangeLog.md Outdated

Copilot AI and others added 6 commits May 21, 2026 15:24

Initial plan

d8e65a4

Add BestEffortAligned storage FD alignment support for VMSS Flex

41be3a8

Agent-Logs-Url: https://github.com/Azure/azure-powershell/sessions/3fdac09c-315d-46f9-a050-f29297b7ba37 Co-authored-by: haagha <64601174+haagha@users.noreply.github.com>

Add tests for VM storage fault domain alignment and update VMSS metho…

0ae0c9d

…ds for alignment support

Add test session records for VMSS and VM tests

7c6925a

Potential fix for pull request finding

6be8b01

asserting on the property being non-null/one-of('Aligned','Unaligned') instead, or using -StorageFaultDomainAlignment 'Aligned' Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

nit fix

09d6983

Dthomas0729 dismissed audreyttt’s stale review via 09d6983 May 21, 2026 19:25

Dthomas0729 force-pushed the copilot/az-compute-add-best-effort-aligned-support branch from 1a5adc8 to 09d6983 Compare May 21, 2026 19:25

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Comment thread src/Compute/Compute/ChangeLog.md Outdated

Shorten changelog

3d6970a

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YanaXu merged commit a260d2f into Azure:main May 22, 2026
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Dthomas0729 commented May 12, 2026

Based on PR #29496 (AI-generated draft) with the following fixes:

New Parameters

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YanaXu commented May 22, 2026