How to recover data from unbootable VM that uses unmanaged disks?

Ian Luu 21 Reputation points

Hi community,

My client is having a trouble where his VM is now unbootable due to error "Error c0000034 applying update operation ... of ..."

His VM was created in Dynamics 365 LCS portal ( and uses unmanaged disks. Now he only wants to recover data from the VM's data disks, not necessarily repair the OS disk.

I have spent sometime tinkering around with my own test VMs (Also created in LCS portal) which initially use unmanaged disks, and observe the following:

  1. I can detach the unmanaged data disks off the VM (Go to VM > Disks > Click Edit > Detach), but cannot find those unmanaged data disks anywhere in the resource group afterward. When using two other VMs, one with unmanaged disks, and one with managed disks, both cannot find those detached unmanaged disks to add.
  2. I cannot find the VHD file of this VM's OS disk inside the Azure Storage Explorer desktop app, according to this article: I can, however, find the VHD files of the VMs that have migrated to managed disks, both OS disks and data disks

The above findings leave me with an impression that, at the moment, Azure seems to have dropped the VHD infrastructure entirely for unmanaged disks? Can someone confirm this please?

I can migrate my bootable VMs to managed disks just fine, albeit the process seems to have reinstalled the OS on the OS disk (I lost my D365 Finance and Operation app as well as the Visual Studio Code subscription). After migration, I can detach the attach the managed data disks very easily.

To sum up, I think data recovery with the VM using unmanaged disks is not feasible now. Therefore, I would like to know:

  1. Is it possible to migrate the unbootable VM's disks from unmanaged disks to managed disks, considering the VM current state?
  2. Will the migration process lose data from the data disks?

As the unbootable VM is of the client, I cannot experiment with it obviously, so I would like to have insights from other more knowledgeable people on here.

Thank you very much.

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Accepted answer
  1. deherman-MSFT 35,241 Reputation points Microsoft Employee

    @Ian Luu
    I confirmed unmanaged disk VHD are still showing in the storage account. Its possible that your disk is in a different container or storage account. You can confirm the container and storage account that the disk is located in by clicking on the disk and navigating to the bottom to investigate the URI.

    Since you are using Dynamics 365 I also recommend posting your question on their dedicated forum. As perhaps there is some nuance to that product that I am not aware of.


    Hope this helps! Let us know if you have further questions or issues and we will do our best to assist.


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

    2 people found this answer helpful.

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