How to Migrate 40TB OneDrive Data Without Loss (Real Case Study)

Symptoms of OneDrive Migration Issues

Several problems might occur during a large-scale OneDrive migration. Some of them are listed below.

• Users might notice that files arrive at the destination with incorrect or missing timestamps.
• Moreover, shared links from the source tenant may stop working after the migration completes.
• Even when the user mapping is not configured correctly, permissions might fail to transfer.
• Additionally, you might find certain files or folders completely missing from the target account.
• The migration job might stall or silently skip large files without reporting any error.
• Also, any truncation in the version history might affect the migration.

How to Migrate OneDrive Data Without Loss

In this section, we will mainly focus on the most effective methods to accomplish OneDrive large-scale migration without any data loss.

• Restore from Backup Before Migration
• Use Microsoft SharePoint Migration Tool (SPMT)
• Using an Advanced Software

Read through each of these methods carefully and try them as per the cause of the problem. In case the manual methods do not help you, it is better to use the automated software mentioned below for the same.

Fix 1: Recover OneDrive Data from Previous Backup 

You can recover any accidentally deleted or overwritten files by restoring them from a OneDrive or Microsoft 365 backup before beginning the migration. In case a recent backup is available, users can simply use the Microsoft 365 Admin Center to bring the missing data back to its original state.

Steps to Restore OneDrive Data from Backup

1. Firstly, sign in to the Microsoft 365 Admin Center using your Global Admin credentials.
2. After that, navigate to Users >> Active Users and select the affected user account.
3. Next, click OneDrive >> select the Create link to files option.
4. Now, open the Recycle Bin within the OneDrive folder to see the recently deleted data
5. Furthermore, select all required files and click Restore to return them to their original location.
6. Next, if the files are not in the Recycle Bin, access the Microsoft 365 Backup portal to restore from a point-in-time snapshot.
7. After that, verify that all restored files retain their original metadata, timestamps, and folder structure.
8. At last, confirm the data is intact before proceeding to the next step in the migration process.

Fix 2: Use Microsoft SharePoint Migration Tool (SPMT) for Bulk Migration

In case you are migrating from an on-premises file server or a legacy SharePoint environment into OneDrive, you can use Microsoft’s free SharePoint Migration Tool to perform the transfer in batches. In this method, SPMT will scan the source data to detect if there is any path length error, unsupported file types, or permission issues before moving any file to the destination.

Steps to Migrate OneDrive Data Using SPMT

1. Download & install the SharePoint Migration Tool from the Microsoft Download Center.
2. Launch SPMT >> select the migration source type, such as a file share, SharePoint Server site, or local folder.
3. Use the valid Global Admin credentials for authentication.
4. Run a pre-migration scan to identify files that exceed 400 characters.
5. Adjust the packaging size settings based on Microsoft’s recommended values.
6. Test the migration with a small batch of data before migrating the 40TB dataset.
7. Start the migration process in scheduled batches during off-peak hours.
8. At last, download the final migration report >> cross-check error logs for any skipped or failed items.

Fix 3: Run a Pre-Migration Audit and User Mapping

If the migration is failing due to permission gaps or mismatched accounts, you can run a structured pre-migration audit to identify and resolve all mapping and path issues before any data moves. In this method, the source tenant is scanned for path violations, unsupported files, and sharing permission conflicts to prevent carry-over errors at the destination.

Simplified Steps to Perform a Pre-Migration Audit

1. Sign in to the Microsoft 365 Admin Portal on your system.
2. After that, navigate to Users >> Active Users >> Export to get a full list of accounts.
3. Identify accounts that exceed the storage quota on the target tenant.
4. Run a folder-path scan to flag any paths that exceed 400 characters.
5. Identify all external sharing links & anonymous share links within the source tenant.
6. Check for unsupported file types, including .tmp, .dll, and .lnk files that OneDrive will reject.
7. Create a CSV mapping file that aligns every source email address to a valid licensed account on the destination tenant.
8. At last, resolve all identified issues in the source environment before initiating the migration job.

Conclusion

In the above article, we discussed the potential causes of data loss during a large-scale Microsoft OneDrive migration. Along with that, we explored various manual troubleshooting methods and an advanced automated tool to migrate OneDrive data without loss. In case you face any issues while using the software, contact our tech support team for personalized assistance.

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About The Author:

Rohan Wiese

Rohan Wiese is a Technical Writer at Aryson Technologies. He is an expert Email Forensic, Cloud Computing, and a passionate nerd with over 10 years of experience in technical content writing. He writes about Cloud Migration, Database Recovery, Email Backup, Windows, Mac, and Tech.