Hello Microsoft Community,

I am currently working on designing and executing a large-scale SharePoint Online restructuring and migration project, and I would appreciate hearing from others who have managed similar enterprise migrations.

This is not a simple document migration. It involves restructuring an existing SharePoint environment into a new information architecture while preserving business continuity, permissions, metadata, version history, and user access.

Current Environment

Our existing SharePoint Online environment contains approximately:

2.7 TB of content

More than 114,000 files

Over 19,000 folders

Multiple document libraries

Deep folder hierarchies

Large media files

Thousands of long file paths

Multiple business units that need to be separated into dedicated SharePoint sites

The migration also requires redesigning the overall information architecture rather than performing a simple lift-and-shift. The planning document includes a phased approach for restructuring sites, libraries, governance, and long-term lifecycle management.

High-Level Migration Strategy

Instead of migrating everything into one destination site, we are creating multiple SharePoint Online sites based on business functions.

For example:

Business Unit A

Business Unit B

Client Sites

Operations

Archive

Each site contains multiple document libraries that map to the existing business structure.

The migration is divided into three phases:

Phase 1

Create new SharePoint sites

Create document libraries

Configure permissions

Preserve folder structure

Copy all content

Preserve version history where possible

Phase 2

Archive completed projects

Remove obsolete content

Move large media files

Implement lifecycle management

Phase 3

Rename projects

Introduce metadata

Reduce folder depth

Improve governance

Simplify navigation

Current Technical Challenges

The biggest technical challenges include:

1. Version History

We want to preserve complete document version history wherever possible.

Has anyone successfully migrated full version history using:

SharePoint Migration Tool

PnP PowerShell

Microsoft Graph

Migration Manager

Third-party tools

What limitations did you encounter?

2. Sharing Links

Many documents and folders already have sharing links that are referenced in external systems.

Our current idea is to generate a mapping such as:

Old URL → New URL

Then update those references after migration.

Has anyone implemented this successfully?

3. Long Paths

The source environment contains thousands of paths exceeding traditional Windows path limits.

Although SharePoint Online supports longer URLs, we're concerned about:

Sync issues

OneDrive client limitations

Third-party integrations

User experience

How have others approached this?

4. Validation

Our current validation plan includes comparing:

Source file count

Destination file count

Folder count

File sizes

Version history

Failed items

We are also planning automated reporting and notifications whenever validation fails.

Are there additional validation steps you would recommend?

5. Automation

Our migration is being automated using PowerShell.

Current features include:

Folder-by-folder migration

Detailed logging

CSV reports

Retry logic

Error handling

Validation after each batch

Email notifications on mismatches

Has anyone implemented additional automation that significantly improved migration reliability?

6. Permissions

We are planning to migrate from direct user permissions to Microsoft Entra ID security groups wherever possible.

For large enterprise environments, what permission model has worked best for long-term governance?

7. Migration Scheduling

Because of the volume of data, we are planning weekend migration windows.

For those who have migrated multi-terabyte SharePoint environments:

Did you migrate library-by-library?

Folder-by-folder?

Site-by-site?

Parallel migrations?

What approach gave the best balance between speed and reliability?

Questions for the Community

I would greatly appreciate feedback on the following:

What migration approach worked best for environments larger than 2 TB?

Which Microsoft tools did you use?

Did you rely solely on PnP PowerShell or combine multiple tools?

How did you validate that no content was lost?

How did you preserve version history?

How did you handle sharing links?

What would you do differently if you repeated the project?

Are there any Microsoft 365 limitations or best practices that we should consider before execution?

Final Thoughts

Our goal is not just to migrate files, but to build a cleaner, scalable, and governed SharePoint Online environment that will support future growth.

Any guidance, lessons learned, Microsoft recommendations, or references to similar enterprise migration projects would be greatly appreciated.

Thank you in advance for your insights!

This looks like a well thought-out migration plan. One lesson from a large migration I was involved in was not to rely only on technical validation.

Along with comparing file counts, sizes, version history, and permissions, we also ran a pilot migration with a small group of business users before moving an entire department. They validated that documents opened correctly, metadata was usable, search results looked right, and existing business processes still worked as expected.

Another thing that helped was scheduling a final delta migration just before cutover. That reduced the amount of new or modified content that needed to be synchronized during the migration window and minimized downtime for users.
If your environment has many workflows or Power Automate integrations, I'd also include those in the validation checklist because they are easy to overlook even when the files themselves migrate successfully.

Overall, your phased approach and move toward Microsoft Entra ID security groups looks like a solid long-term strategy. I'd be interested to hear which migration tool you eventually choose and how it performs with version history at this scale.

Community site session details

Enterprise SharePoint Online Migration Restructuring Looking for Best Practices from the Community

Current Environment