nested VM keeps shutting down showing a hard disk error.

Question

nested VM keeps shutting down showing a hard disk error.

HCML TEST 0

Hello - nested VM keeps shutting down showing a hard disk error.

Since this is Azure the obvious solution of changing an SSD is not ...... available !

Jilakara Hemalatha 14,115 Reputation points Microsoft External Staff Moderator

2026-04-13T01:32:05.32+00:00
Hello HCML,

To better understand the issue, could you please help with the following details:

Are you running a nested VM inside an Azure VM? If yes, which hypervisor is being used?

What is the exact error message observed related to the hard disk?

Does the issue occur during boot or while the VM is running?

Were there any recent changes (updates/configuration) before the issue started?

Is the parent Azure VM stable without any performance or disk-related alerts?

Could you check and share logs from the nested VM (Event Viewer / system logs)?

What is the disk type and VM size being used in Azure?

This will help us determine whether the issue is related to the nested VM environment or the underlying Azure infrastructure. Additionally, could you please check the private message and provide necessary details.

Answer recommended by moderator

HCML TEST 0

Hello All,

User's image

Thanks for replying. The above was the error in Hyper-V.

I resolved it by pure chance. I was logging back in to the Azure VM when I noticed in the bottom right corner a message that stayed there no more than 2 seconds - literally, as I RDP'd onto the Azure VM (Win2019) by the time the screen had drawn the message was already there and before the taskbar had populated the message had gone. But the message was clear : Running low on Premium SSD.

And, indeed, the SSD allocated to that nested VM only had 8Mb left, so I upgraded its size through the Azure portal and no more problems.

Lesson learnt : I'll set up an Azure Monitor alert to email me when storage gets low.

Jilakara Hemalatha 14,115 Reputation points Microsoft External Staff Moderator

2026-04-13T06:56:26.7633333+00:00

Hello HCML TEST

Thank you for the update, we’re glad to hear the issue has been resolved after addressing the disk space limitation.

1 additional answer

Your answer

Jilakara Hemalatha 14,115 Reputation points Microsoft External Staff Moderator

2026-04-13T01:32:05.32+00:00

Hello HCML,

To better understand the issue, could you please help with the following details:

Are you running a nested VM inside an Azure VM? If yes, which hypervisor is being used?

What is the exact error message observed related to the hard disk?

Does the issue occur during boot or while the VM is running?

Were there any recent changes (updates/configuration) before the issue started?

Is the parent Azure VM stable without any performance or disk-related alerts?

Could you check and share logs from the nested VM (Event Viewer / system logs)?

What is the disk type and VM size being used in Azure?

This will help us determine whether the issue is related to the nested VM environment or the underlying Azure infrastructure. Additionally, could you please check the private message and provide necessary details.
Jilakara Hemalatha 14,115 Reputation points Microsoft External Staff Moderator

2026-04-13T06:56:26.7633333+00:00

Hello HCML TEST

Thank you for the update, we’re glad to hear the issue has been resolved after addressing the disk space limitation.

Answer 1

Start by confirming where the error originates. If the host Azure VM is stable and only the inner VM crashes, focus inside the nested VM. Check its system logs for disk or filesystem errors. On Windows check Event Viewer for disk, NTFS, or controller errors.

Corruption is common after improper shutdowns or aggressive caching. Run a filesystem repair inside the nested VM. For Linux, run fsck -f /dev/<disk> and for Windows, run chkdsk C: /f /r

If the disk is mounted, you may need to attach it to another VM or boot into recovery mode.

Nested virtualization on Azure depends on the outer VM’s disk and caching mode. If the outer VM uses host caching (especially ReadWrite), it can introduce inconsistency under nested workloads. Switch the Azure disk caching mode to ReadOnly or None and redeploy the VM. Also verify the disk SKU; Standard HDDs are prone to latency spikes that look like disk failure. Premium SSD or Ultra disks are much more stable.

Check that the outer VM size supports nested virtualization properly (Dv3, Ev3, or newer). Older or constrained SKUs can produce intermittent I/O timeouts under nested load.

If the issue started after resizing or moving the VM, the disk attachment order or controller type may have changed. Ensure the nested hypervisor is still using the correct virtual disk controller (e.g., virtio vs IDE vs SCSI). Mismatches can trigger boot-time disk errors.

If corruption keeps recurring, snapshot the Azure disk, create a new managed disk from the snapshot, attach it to a clean VM, and validate data integrity. This helps separate persistent corruption from runtime instability.

If the above response helps answer your question, remember to "Accept Answer" so that others in the community facing similar issues can easily find the solution. Your contribution is highly appreciated.

hth

Marcin

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nested VM keeps shutting down showing a hard disk error.

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