Cannot Migrate Flash Booted VM on Hyper-V 2019

Product version: 11.1

Last modified: 7 October 2025

Problem

When attempting to migrate a Flash-booted VM on Hyper-V 2019, the operation may fail during virtual disk creation or migration with the following error message:

Failed to convert the virtual disk

Background

This error occurs because of the following limitations:

  • Flash-booted VMs cannot be moved between standalone Hyper-V hosts.

  • Migration is supported only within a Hyper-V cluster, and only when the VM is powered off.

  • Pass-through disks are not supported for migration by Microsoft.

  • Disk I/O issues during conversion may also cause failures.

Solution

To migrate a Flash-booted VM within a Hyper-V cluster:

  1. Ensure the VM is powered off before migration. If not, shut down the VM.

  2. Create a new Virtual Disk (VHDX) if needed:

  • Open Hyper-V Manager.

  • Go to VM Settings > Hard Drive Properties.

  • Under Media, select Virtual hard disk > New.

  • In the New Virtual Hard Disk wizard, specify the following parameters:

    • Disk Format: VHDX

    • Disk Type: Dynamically expanding

    • Name/Location: Provide a new name and storage path

    • Configure Disk: Select Copy the contents of the specified physical disk and choose the required disk

  1. Optional. If the VM uses a pass-through disk, create a new virtual disk and manually copy data. Pass-through disks cannot be migrated directly.

  1. After migration, confirm that the VM appears correctly in the cluster and can be started as expected.

Notes

  • Migration is supported only between hosts in the same Hyper-V cluster.

  • Migration between standalone hosts is not supported.

  • Ensure the VM is powered off before starting migration.