Migrate VM to Managed Disks Fails

Bruno 21 Reputation points
2020-07-22T18:55:34.207+00:00

Hi,

Successfully migrated exiting production VM and Data storage from classic to ARM. Now, when attempting to migrate disks from unmanaged to managed I get this error: Failed to migrate the virtual machine 'VM'. Error: VHD footer 'Current Size' field validation failed. VHD for disk 'VM_os_dsk.vhd' with blob https://blah.blob.core.windows.net:8443/vhds/os_dsk.vhd specifies size (37762367488) which does not match VHD blob size (37763416576) - VHD Footer Size (512). The VM is currently working fine.

I've tried downloading the vhd using Azure Storage Explorer multiple times, but it fails right before it completes because a size mismatch issue. Even turning off the MD5 check option... I get the same problem.

After trying multiple times I was able to download the VHD using a SAS url, however now when I use resize-vhd, I'm getting error message that the VHD is corrupt and unreadable, even though the VM in azure is running perfectly fine. I've tried downloading the VHD a couple of times, still the same error.

What am I doing wrong, can someone help? How can I migrate this VM to managed disks?

Thanks for your help.

Azure Migrate
Azure Migrate
A central hub of Azure cloud migration services and tools to discover, assess, and migrate workloads to the cloud.
716 questions
Azure Disk Storage
Azure Disk Storage
A high-performance, durable block storage designed to be used with Azure Virtual Machines and Azure VMware Solution.
571 questions
0 comments
Accepted answer
  1. deherman-MSFT 33,141 Reputation points Microsoft Employee
    2020-07-23T17:33:06.603+00:00

    @Bruno-8416 It appears you will need to resize the VHD in order for this to work properly. You can try using VHD Resizer to accomplish this. Please note I recommend to not run this on the production system.

    https://blogs.msdn.microsoft.com/devkeydet/2012/07/05/resizing-an-azure-vm-vhd-file/

    Hopefully this helps!

    Please don’t forget to "Accept the answer" wherever the information provided helps you, this can be beneficial to other community members.

    0 comments

2 additional answers

Sort by: Most helpful
Most helpful Newest Oldest
  1. deherman-MSFT 33,141 Reputation points Microsoft Employee
    2020-07-22T21:36:31.537+00:00

    @Bruno This document walks through identifying and mitigating this issue. Please try the mitigation steps and see if it fixes your issue.

    https://learn.microsoft.com/en-us/azure/virtual-machines/windows/migration-classic-resource-manager-errors#vm-with-data-disk-whose-physical-blob-size-bytes-does-not-match-the-vm-data-disk-logical-size-bytes

    --------------

    Please don’t forget to "Accept the answer" wherever the information provided helps you, this can be beneficial to other community members.

  2. Bruno 21 Reputation points
    2020-07-24T23:14:06.88+00:00

    Thank you! I was able to successfully resize the vhd and create managed disks from it.