Azure Docs

Migrating Azure Managed Disks

This document provides guidance on migrating your Azure Managed Disks. We cover various scenarios, including migrating from unmanaged disks to managed disks, migrating disks between subscriptions or regions, and moving data to different disk types.

1. Migrating from Unmanaged Disks to Managed Disks

This is a common migration path for older deployments. Azure provides tools to automate this process.

Methods:

• Azure Resource Manager (ARM) Templates: You can detach an unmanaged disk, create a managed disk from the VHD, and then attach the managed disk to a new or existing VM. ARM templates can script this process.
• Azure Portal: The portal offers a straightforward wizard to convert unmanaged disks to managed disks.
• Azure CLI/PowerShell: Scripting the conversion is also possible using Azure command-line tools.

# Example using Azure CLI for conversion
az vm deallocate --resource-group MyResourceGroup --name MyVM
az vm convert --resource-group MyResourceGroup --name MyVM --out managed
az vm start --resource-group MyResourceGroup --name MyVM

2. Migrating Managed Disks Between Regions

Moving managed disks to a different Azure region often involves creating a copy of the disk in the target region.

Steps:

1. Create a Snapshot: Take a snapshot of the source managed disk.
2. Copy Snapshot to Target Region: Use the az snapshot create command with the --location parameter to copy the snapshot to the desired region.
3. Create Managed Disk from Snapshot: Create a new managed disk in the target region from the copied snapshot.
4. Attach to VM: Attach the new managed disk to a VM in the target region.

3. Migrating Managed Disks Between Subscriptions

Migrating disks across subscriptions typically involves exporting the VHD and then importing it into the target subscription.

Process:

• Export VHD: Use the Azure portal or CLI to generate a Shared Access Signature (SAS) URI for the managed disk and download the VHD.
• Upload VHD to Target Subscription: Create a storage account in the target subscription and upload the VHD.
• Create Managed Disk: Create a new managed disk from the uploaded VHD in the target subscription.
• Attach to VM: Attach the new disk to a VM in the target subscription.

4. Migrating to Different Disk Types (e.g., HDD to SSD)

You can upgrade or downgrade the performance tier of your managed disks by migrating data to a new disk of the desired type.

Recommended Approach:

1. Create a new disk of the target type (e.g., Premium SSD).
2. Migrate data from the old disk to the new disk. This can be done using tools like Robocopy (for Windows) or rsync (for Linux) while the VM is running or in a maintenance window.
3. Detact the old disk and attach the new disk to your VM.
4. Update boot order or mount points if necessary.
5. Delete the old disk once you confirm the new disk is functioning correctly.

Alternatively, you can create a snapshot, create a new disk from the snapshot with the desired type, and then swap the disks.

Tools and Considerations

Best Practices

• Backup: Always back up your data before initiating any migration.
• Test: Perform a test migration in a non-production environment first.
• Downtime Planning: Schedule migrations during low-traffic periods or maintenance windows.
• Monitoring: Monitor disk performance and application health during and after the migration.
• Documentation: Document the entire migration process for future reference.