Moving off the office file server: what to sort out before anything goes to SharePoint

Copying the files is the easy part. Microsoft provides a tool for it in the SharePoint admin centre. What goes wrong in these moves is nearly always something that was already wrong on the old drive: folders nested ten levels deep, file names with characters SharePoint won't take, years of one-off folder permissions, and a single "everything" share that nobody has tidied since it was set up. Sort those out first and the move itself is a quiet weekend.

1. Decide what goes where before you copy anything

A file server is usually one big tree. In Microsoft 365 you have two places to put things, and they do different jobs:

• OneDrive is each person's own working space. Drafts, personal notes and files they would have kept on their desktop go here.
• SharePoint sites (which is also where files in a Teams channel live) are for shared work. Split them by who needs access: Finance, Projects, HR, Operations. Don't split them by how the old folders happened to be laid out.

The mistake I see most is rebuilding the whole S: drive as one SharePoint library. It works on day one, and it also brings every old problem across with it. This is also the cheapest moment to leave things behind. Finished projects from years ago can go to a read-only archive site instead of the live one.

2. Check you have the storage

On the Microsoft 365 Business plans, SharePoint storage is a shared pool for the whole organisation: 1 TB plus 10 GB for each licence. With 15 licences that is about 1.15 TB, shared across every SharePoint site. OneDrive storage is separate and per person. Measure the server before you plan anything. If the shared data is bigger than the pool, you will need to archive some of it or buy extra storage.

3. Clean up file names and folder depth

Two limits catch most offices:

• Characters. " * : < > ? / \ | aren't allowed in file or folder names, and neither are leading or trailing spaces. Windows already blocks most of these, but Mac users and some scanners and older apps create them anyway.
• Path length. The full path inside SharePoint, including the site and library name, every folder and the file name, can't be more than 400 characters. Something like "Clients/2019/ABC Pte Ltd/Project – Phase 2 (revised)/Drawings/Final/Final v3/…" gets there faster than you would think.

Before a move I run a script against the share that lists every name with a blocked character and every path that is getting close to the limit. Then someone who knows the content renames or flattens those folders. A machine shouldn't guess at that. Single files over 250 GB are also blocked. In practice that only affects old backup images and raw video.

4. Rethink permissions instead of copying them

File servers collect permissions one folder at a time: "only Mary and the boss can open this one." Copying all of that across makes SharePoint slow to manage and hard to audit. Microsoft supports up to 50,000 items with their own permissions in a library, but recommends staying under 5,000. Once a library or folder has more than 100,000 items, you can no longer change its permissions separately at all.

What works for small teams: set access at the level of the site, and keep the few truly restricted areas (payroll, HR files, directors' papers) on sites of their own. Write down who should have access to each site before the move, and get the business owner to agree to it. That list is worth more than any tool.

5. Plan what people will sync, and what shouldn't move at all

Staff will want the files to show up in File Explorer like the old drive. The OneDrive sync app does that, but Microsoft recommends syncing no more than 300,000 items across everything a person syncs. A preview raises that to 1,000,000. Everyone syncing every library is how laptops end up with sync errors. Sync only the libraries a person works in every day and open the rest in the browser or Teams.

Some things on a file server aren't really documents. A shared Access database, a desktop accounting company file that several people open over the network, CAD drawings with linked references: sync works on whole files, so two people working in the same one at the same time leads to conflicts. Each of these needs its own plan. Sometimes that's the cloud version of the software, sometimes a small server or virtual machine that stays. Find them early. They are usually the reason a "simple" migration slips.

6. Do the move in two passes

For a network file share, Microsoft's tool is Migration Manager in the SharePoint admin centre. You install a small agent on a Windows machine that can read the share (the source has to support SMB 2.0 or later), point each folder at its new site or OneDrive, and it copies the files and reports on anything it couldn't move. The same tool can also bring content across from Google Drive, Dropbox, Box and Egnyte.

The order I follow:

• Copy everything once, a week or so ahead, and have each team check its own site.
• Fix what the reports flag. Usually that means names, paths and anything that was skipped.
• On switch-over day, make the old share read-only, copy what changed since the first pass, and point people to the new locations.
• Keep the old server running read-only for a few weeks before anything is wiped.

7. Sort out backup before you switch the old server off

The server probably had some kind of backup, even if nobody has tested it lately. Microsoft 365 keeps deleted files and old versions for a limited time, but that is not the same as a backup you control. I've written about the difference in the FAQ: does Microsoft 365 back up our files?

If you'd like help

I do file server and shared drive moves as part of cloud migration work for Singapore SMEs. That covers planning the site layout, the clean-up scripts, the copy itself and the first weeks of questions from staff. If you are weighing this up, send me a short description of what's on the server, roughly how big it is and how many people use it.

Sources

• Microsoft Learn: SharePoint limits (storage pool, 400-character path, 250 GB files, permission limits)
• Microsoft Support: Restrictions and limitations in OneDrive and SharePoint (invalid characters, sync limits)
• Microsoft Learn: Migrate your file shares to Microsoft 365 with Migration Manager