Migrating a File Server or NAS to SharePoint: A Small Business Guide

Staff working from home have to start the VPN before they can open the S: drive. Files take ages to open over it, and someone always has the spreadsheet locked. The old server in the cupboard is out of warranty and getting louder. At some point the question comes up: should all of this just live in SharePoint?

The short answer: for most offices, moving shared documents from a file server or NAS into SharePoint and OneDrive makes life easier, because files open from anywhere, several people can edit at once, and there is no box in the cupboard to maintain. But not everything should move. Huge design files, accounts databases and anything that needs a drive letter may be better left on local storage. A good migration starts by deciding which is which.

What SharePoint actually gives you

SharePoint is the file storage behind Microsoft 365. Each team gets a site with its own document library and permissions. Microsoft Teams uses the same libraries behind its Files tab, and staff can sync any library to File Explorer on their PC so it feels like a normal folder. You also get version history on every file, sharing links for clients, and search across everything you are allowed to see. If you already pay for Microsoft 365 Business Basic, Standard or Premium, SharePoint storage is included.

Should everything move?

Usually move to SharePoint	Often better left on a NAS or server
Office documents, PDFs, templates, policies	Large CAD, Revit, video and photo libraries that are edited all day
Project folders that remote staff need	Accounts databases such as Sage 50 that must not sit in a sync folder
Client documents you share by link	Software that expects a mapped drive letter
Department folders with clear owners	Archives of old files nobody opens but you must keep

Many offices end up hybrid: everyday documents in SharePoint, with a smaller NAS for the heavy or awkward data. If that is you, our guide to setting up a small office NAS with proper permissions covers the local side.

The limits that catch people out

• Path length. SharePoint limits the full path of a file, including site and folder names, to 400 characters. Deep folder trees with long names from an old server can break this.
• Blocked names and characters. Characters such as " * : < > ? / \ | are not allowed in file names, and names like CON, PRN, desktop.ini and anything starting with ~$ are blocked or skipped.
• File size. The upload limit is 250 GB per file, which is rarely an issue for documents but matters for video and backups.
• Sync volume. Microsoft advises syncing no more than about 300,000 files across all the libraries one PC syncs. Above that, the OneDrive app can slow down. Staff should sync only the libraries they use, not the whole company.

A pre-migration scan finds these problems before they turn into missing files.

Permissions: redesign, do not copy

Old file servers build up years of one-off permissions: a subfolder only Sarah can open, a folder shared with someone who left in 2019. Copying all of that into SharePoint copies the mess. We prefer to redesign:

• One site per department or major function, for example Finance, HR, Operations, Projects.
• Access granted through Microsoft 365 groups, so adding a new starter to the Finance group gives them the Finance site.
• Few or no unique permissions inside a site. If a folder needs different access, it usually wants its own site or library.
• External sharing set per site, so client sharing is allowed where it is needed and switched off for HR.

The Microsoft tools

Microsoft provides two free tools for moving files from a file share into SharePoint and OneDrive:

• SharePoint Migration Tool (SPMT) runs on a PC or server that can see the file share. It copies files and folders into SharePoint libraries, keeps created and modified dates, and can run again later to copy only what has changed.
• Migration Manager in the SharePoint admin centre does the same from a central console, with agents installed near the data. It suits larger moves and can also bring files across from Google Drive, Dropbox and Box.

Both tools do the copying well. The work that decides whether the move goes smoothly is the planning around them.

A cutover plan that does not ruin Monday

1. Audit. Measure how much data there is, how old it is, who uses which folders and what breaks the SharePoint limits.
2. Clean up. Archive folders nobody has opened in years, remove duplicates and shorten silly paths. Less data means a faster, cleaner move.
3. Design the sites and permissions with the department heads.
4. Pilot with one team for a week to catch problems early.
5. Bulk copy the rest during the week while the old share stays live.
6. Final changes copy on a Friday evening, then set the old share to read-only.
7. Monday morning: libraries synced or added as shortcuts on every PC, Teams set up, and someone on hand to answer "where has my folder gone?"
8. Keep the old data read-only for at least a month, then archive it with a backup.

After the move

SharePoint keeps version history and a recycle bin, but Microsoft 365 is not a backup in the full sense. Retention is limited, and a compromised account or a big mistake can still cost you data. A separate Microsoft 365 backup is worth the small monthly cost. If you keep a NAS for the heavy files, back that up too, as covered in our guide on backing up a NAS to the cloud.

Moving email at the same time? Our Microsoft 365 email migration guide covers moving from hosting-company email, Zoho, Gmail and GoDaddy.

How we run SharePoint migrations

We start with a short audit of your file server or NAS: how much is there, who uses what, and what will not fit SharePoint's rules. We explain what should move and what should stay local, agree the site structure with you, then run the copy, the cutover and the Monday-morning support. Our Microsoft 365 migration service covers offices across London, Berkshire and Surrey, and our Microsoft 365 page explains what else the platform can do for you.

Frequently Asked Questions

How long does a file server to SharePoint migration take?

For a small office with a few hundred gigabytes, the copying itself usually runs over a few days in the background. The planning, clean-up and cutover make up most of the work, and the switch itself is normally done over a weekend.

Will file dates and versions be kept?

The Microsoft migration tools keep created and modified dates. Version history only starts once files are in SharePoint, so keep the old data read-only for a while in case you need an older copy.

Can we keep using a mapped drive letter?

Not in the old way. Staff sync the libraries they use to File Explorer, or add shortcuts to their OneDrive. Software that truly needs a drive letter is usually better left on a local server or NAS.

Is SharePoint better than a NAS?

For documents and remote teams, usually yes. For very large files used all day, or software that needs local storage, a NAS is often better. Many small offices use both.

Do we need to back up SharePoint?

We recommend it. Microsoft keeps deleted items for a limited time, so a separate backup protects you against mistakes, compromised accounts and ransomware.