Azure Migrate: Deployment issue — Data source conflict preventing appliance registration

Question

Azure Migrate: Deployment issue — Data source conflict preventing appliance registration

Kyle-6225 0

Problem description

I am unable to register an Azure Migrate appliance to an existing project. During the registration process, the API returns a BadRequest error indicating that a data source already exists for the site. I suspect this is due to a prior discovery run using the Data Collector utility, which created an existing data source record. I attempted to remove the Collector from the migration project but there is not a remove/delete option.

Environment

Azure Migrate assessment project deployed in Azure Resource Manager. The affected resource is an appliance within the same resource group, region not specified.

What I've already tried

I have completed a one-time inventory collection using the Data Collector utility. I confirmed that all required URLs are whitelisted, and I have the necessary Azure permissions (Contributor level). I also verified source prerequisites such as network ports and service account rights. During appliance setup, the registration step fails with the same error. I attempted to retrieve diagnostic logs from the Azure Migrate project, but no data was found.

Current status

The registration process continues to fail with the 'data source already exists' error. I am seeking guidance on how to identify and remove the conflicting data source resource to resolve the registration issue.

Ravi Varma Mudduluru 12,540 Reputation points Microsoft External Staff Moderator

2026-08-25T01:14:54.2833333+00:00

Hello @Kyle-6225

Thank you for contacting us about the Azure Migrate issue. We have begun looking into it and will share our suggestions with you as soon as possible.
Ravi Varma Mudduluru 12,540 Reputation points Microsoft External Staff Moderator

2026-08-27T02:29:19.9333333+00:00
Hello @Kyle-6225

Thank you for reaching out to Microsoft Q&A

Based on the error message ("data source already exists for the site"), it appears that a previous Azure Migrate discovery source or appliance registration is still associated with the Azure Migrate project. This can occur when a Data Collector or appliance was previously used for discovery and its registration metadata remains in the project.

I would recommend the following:

In the Azure portal, navigate to Azure Migrate > Your Project > Discovery and Assessment > Appliances and verify whether an existing or disconnected appliance is already registered with the project.

From the appliance configuration manager, run the Diagnose and Solve utility. This validates the appliance registration, Microsoft Entra application, project availability, and other Azure Migrate components that are required for successful registration.

If you identify an older appliance that is no longer in use, review whether it can be removed through the Azure Migrate project. Additionally, check Microsoft Entra ID > Enterprise Applications for any stale Azure Migrate appliance registrations that may be associated with the old appliance. Similar Azure Migrate registration issues have been caused by orphaned appliance registrations or service principals left behind after an appliance was deleted without proper cleanup.

If the project no longer shows any appliance, but registration still fails with the same error, the project may contain stale backend metadata for the discovery source. In such cases, creating a new Azure Migrate project and registering the appliance against the new project is often the recommended workaround.

Microsoft Documentation

https://learn.microsoft.com/azure/migrate/troubleshoot-appliance-diagnostic

https://learn.microsoft.com/azure/migrate/troubleshoot-appliance

https://learn.microsoft.com/azure/migrate/troubleshoot-general

If the issue persists after validating the existing appliance registrations and diagnostics. Could you please check the private message and share the requested details there?

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1 answer

Your answer

Ravi Varma Mudduluru 12,540 Reputation points Microsoft External Staff Moderator

2026-08-25T01:14:54.2833333+00:00

Hello @Kyle-6225

Thank you for contacting us about the Azure Migrate issue. We have begun looking into it and will share our suggestions with you as soon as possible.

Answer 1

Hello @Kyle-6225

The behavior you're seeing is consistent with a previous Azure Migrate discovery/appliance registration still being associated with the existing project.

The important point is that Azure Migrate currently doesn't support deleting an individual registered appliance from a project. Microsoft documents that a project can have multiple appliances, but you can't simply remove an existing registered appliance from the project through the portal.

You can first confirm whether the previous appliance is still registered:

Azure Migrate → Servers, databases and web apps → Discovery and assessment → Overview → Appliances

Microsoft documents this as the location where you can see the appliances registered with the project and their connectivity status.

If the old appliance/data source appears there, I would not try to manually delete hidden Azure resources or use an unsupported REST/ARM DELETE operation against the data-source resource. That could leave the Azure Migrate project in an inconsistent state.

Also, because you previously used the Data Collector utility, don't assume that Contributor permissions or rerunning appliance registration will remove the existing discovery metadata. Azure Migrate stores discovery metadata as part of the project.

There are essentially two supported paths.

1. Preserve the existing Azure Migrate project

If you need to retain the existing discovery/assessment data, I recommend opening an Azure support request for Azure Migrate and providing the exact BadRequest response from the appliance registration.

In particular, include: Project name, Resource group, Subscription, Region, Existing appliance/data source name, New appliance name, HTTP status: 400 BadRequest, Full error code, Full error message, Correlation/Request ID, and Timestamp (UTC).

If this is an orphaned backend data-source record rather than an active appliance registration, Microsoft support can determine that from the service-side project state.

2. Existing discovery data isn't required

If you can discard the previous discovery/assessment data, creating a new Azure Migrate project is the cleaner option. Azure Migrate supports creating additional projects and registering a fresh appliance against the new project.

If you want to reuse the existing appliance server with the new project, Microsoft says you must reconfigure it using the appropriate Azure Migrate PowerShell installer script, which cleans up the existing appliance components/settings. Then generate a new project key; don't reuse an existing one.

One caution: I wouldn't delete the current project or its resource group unless you're certain you no longer need the existing discovery data and assessments. Deleting the project removes its discovered-server metadata, and project deletion is irreversible.

Microsoft references:

Azure Migrate appliance FAQ

Create and manage Azure Migrate projects

If you can post the complete BadRequest error, including the error code and correlation/request ID (with subscription/tenant details redacted), we can determine whether this is an existing registered appliance conflict or an orphaned data-source record that needs Microsoft support intervention.

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