Resizing from 5th generation to 7th generation Windows VMs

Question

Hello,

I am trying to resize 5th generation Dxads_v5 VMs to Dxads_v7 and 7th generation E series VMs but we get an incompatible disk controller type error because the 5th generation servers have SCSI disks and 7th generation ones are NVMe.

I tried resizing the VM directly, 7th generation servers were not incompatible, then I tried to create a snapshot and create a 7th generation VM from the snapshot but still got the same error.

What are the options I have in this case?

Thanks,

Erdinc

Answer 1

hi Erdinc Bereketoglu & thanks for join me here at Q&A portal,

yeah this is expected. v7 sizes are NVMe-only, and ur existing v5 VM/OS disk was created with SCSI, so Azure cannot just resize it across controller types. Snapshot does not fix it because the disk metadata compatibility stays SCSI. Microsoft docs say newer VM generations support NVMe and the VM or image must be created or configured with NVMe support. Best options is create a new v7 VM from an NVMe-capable marketplace image and migrate apps&data or build a new golden image with NVMe enabled, or prepare the OS for NVMe and recreate the VM with NVMe disk controller where supported. Direct resize from SCSI v5 to NVMe-only v7 usually is not supported. If u need minimal risk, stay on a v6/v7 size that still supports SCSI, if available in ur region or SKU list, or move workload to new NVMe VM. other words snapshot wont convert SCSI to NVMe, u need recreate or migrate with NVMe-ready image or disks.

rgds,

Alex

&

If my answer was helpful pls mark it and additional thx if u follow me at Q&A portal

Answer 2

Hello Erdinc,

Thank you for sharing the details.

We reviewed the behavior, and this appears to be related to a known Azure platform limitation involving disk controller compatibility between older and newer VM series.

The current Dxads_v5 and older E-series VMs use SCSI-based disk controllers, while the newer v7 VM families use NVMe-based controllers. At this time, Azure does not support direct resize or migration operations when the OS disk controller changes from SCSI to NVMe.

Reference: https://learn.microsoft.com/en-us/azure/virtual-machines/sizes/resize-vm?tabs=portal#limitations

Because of this limitation, the following operations may fail with an “incompatible disk controller type” error:

• Direct VM resize from v5 to v7
• Creating a new v7 VM from an existing OS disk
• Deploying a VM from a snapshot or managed image created from the original VM

Although snapshots and managed images can still be created successfully, the underlying OS disk configuration remains SCSI-based, so Azure validation continues to block deployment to NVMe-only VM families.

How can I resize a SCSI-based VM to a remote NVMe-enabled VM of a different size?

Microsoft has recently introduced support for converting certain VMs from SCSI to NVMe, provided the required prerequisites are met. This includes:

• Supported operating system versions (for example, Windows Server 2019 or later)
• Generation 2 VM configuration
• Target VM size that supports NVMe
• Supported Azure VM families and regions

Microsoft provides guidance and scripts to update both the VM size and disk controller type as part of the conversion process.

Reference: https://techcommunity.microsoft.com/blog/sapapplications/moving-linux-and-windows-from-scsi-to-nvme-with-one-easy-command/4427954

https://learn.microsoft.com/en-us/azure/virtual-machines/enable-nvme-remote-faqs?tabs=windows

If the VM does not meet the required prerequisites for SCSI-to-NVMe conversion, the recommended approach would be:

• Deploy a new Generation 2 VM using the target size
• Use migration methods such as Azure Backup restore, Azure Site Recovery (ASR), Azure Migrate, disk copy, or application-level migration to move workloads and data
• Validate application functionality before cutover

This approach ensures the VM is deployed with the correct NVMe-based disk controller configuration from the beginning and avoids compatibility issues with the newer VM generations.

Reference: https://learn.microsoft.com/en-us/azure/virtual-machines/nvme-overview

Hope this helps! Please let me know if you have any queries.