How to Migrate a File Server to SharePoint Online
- Sam Williams
- Mar 29
- 2 min read
Still running a file server in the office or a datacentre? You're not alone. A lot of businesses we work with are in the same boat — years of files on a local server, and the idea of moving it all to the cloud feels overwhelming.
It doesn't have to be. Here's how to plan and execute a migration to SharePoint Online without losing anything.
Clean up before you migrate
Don't migrate the mess. This is the single most important step and the one everyone wants to skip.
Go through your file server and ask: what's current, what's archive, and what's junk? Most file servers have 30 to 50 per cent content that nobody has opened in years.
Delete what's obviously junk. Archive old project files to cheap storage (or a separate SharePoint archive site). Only migrate active, current files to your main SharePoint sites.
Plan your SharePoint structure
Don't replicate your folder structure exactly. This is the second biggest mistake — taking a deeply nested folder tree and recreating it in SharePoint.
SharePoint works better with a flat structure and metadata. Instead of Clients → ACME Corp → 2024 → Invoices, create a document library with columns for Client, Year, and Document Type.
Map your departments or teams to SharePoint sites. Each site gets its own document libraries. Keep it simple — you can always add structure later.
Migration tools
Microsoft provides a free tool called SharePoint Migration Tool (SPMT). It works well for straightforward migrations.
For larger or more complex migrations, tools like ShareGate or MigrationWiz give you more control over mapping, scheduling, and reporting.
Whichever tool you use, run a test migration first. Pick one department or folder set, migrate it, and check that everything looks right.
What to watch out for
File path limits. SharePoint has a 400-character limit on the full file path. If you have deeply nested folders with long file names, some won't make it across. The migration tool will flag these.
Special characters. Characters like # % & in file names can cause issues. Clean these up before migrating.
Permissions. File server permissions don't map directly to SharePoint. You'll need to set up new permissions in SharePoint based on your site structure.
File types. Some file types are blocked in SharePoint by default (like .exe files). Check Microsoft's list if you have unusual file types.
The rollout
Don't do a big-bang migration. Migrate one team at a time. Let them use SharePoint for a week while the file server is still available as a read-only backup.
Once everyone is comfortable, decommission the file server. Keep a final backup for 90 days just in case.
The migration itself usually takes a few days to a few weeks depending on how much data you have and your internet speed.
File server migrations are one of our most common projects. We handle the planning, cleanup, migration, and training so your team isn't disrupted. Reach out if you want a quote.
