Migrate unmanaged disks to managed disks

Question

Hi,

I have a VM in Azure with unmanaged disks (OS - 152 GB, datadisk 1 - 512GB and datadisk 2 - 1023GB), static IP, and as end of support for unmanaged disks will end this year, I need to migrate these disks to managed disks but I have some questions.

I would like to know the potential impact of this migration and any specific areas that need attention during the process? I have searched for information regarding the impact but haven't found any relevant details.

Are there any compatibility issues or dependencies I need to consider when migrating my VM's disks?

Could you please clarify if this process automatically creates new managed disks and transfers the data from the unmanaged disks? I am asking because I would like to know if any data loss is possible?

How much downtime should expect?

Thank you,

Ramona

Answer 1

Hello Ramona Istrate,

Welcome to Microsoft Q&A Forum. Thanks for posting your query here!

I understand that you would like to Migrate unmanaged disks to managed disks.

If you are encountering difficulties with the migration task, we advise you to deallocate the virtual machine. Please be informed that the primary consequence of this action is the downtime necessary to deallocate the VM and subsequently reattach it to the new managed disks. The exact downtime depends on the VM size, disk size, and network conditions. Expect some downtime, typically measured in minutes.

However, we recommend you follow the below steps to Migrate unmanaged disks

• Perform a full VM backup.
• Deallocate the VM using the Azure portal, Azure CLI, or PowerShell.
• Use the "Migrate to managed disks" option in the Azure portal or the appropriate command-line tool to initiate the migration.
• After the migration is complete, re-create the VM using the new managed disks.
• Thoroughly test the VM's functionality after the migration to ensure everything is working as expected.
• For most VMs, the downtime for this process should be within a few minutes.
• The size of the disks, network conditions, and the overall workload on the Azure platform can influence the actual downtime.

Please be informed that There might be a very brief interruption in service while the VM is deallocated and reattached. Before migration, ensure all applications on the VM are in a consistent state to minimize the risk of data corruption.

Answers for your questions.

1. Yes, the migration process automatically creates new managed disks.
2. The migration process essentially "converts" the existing unmanaged disks into managed disks. The data itself is not physically transferred; the underlying storage is changed.
3. Data loss is minimal if the migration process is performed correctly, and you have a recent backup.

Additional information: Below is the Documentation on Backup and disaster recovery for Azure unmanaged disks

https://learn.microsoft.com/en-us/azure/virtual-machines/page-blobs-backup-and-disaster-recovery

Let me know if you have any further quarries we are here at your service!

Answer 2

Hi. The migration process automatically creates managed disks, transfer all data and update the VM. However, it is a good point to back up your data before the migration and also delete old disk resources (VHD + storage account) after migration. 

 

Regarding the downtime, New disks will be created without downtime, but in case you have a lot data, you may see some impact to read latency. VM restart will take some time (deallocation and allocation of the VM).
https://learn.microsoft.com/en-us/azure/virtual-machines/faq-for-disks?tabs=azure-portal#migrate-to-managed-disks

Also about the IP, because you mention it is static, I think it will be the same, but you need to check and assign it again if it is necessary. 

Here some information about the migration https://learn.microsoft.com/en-us/azure/virtual-machines/windows/convert-unmanaged-to-managed-disks  Please visit it also if you did not do so already.