10 Reasons SharePoint Is Not a File Server

Line-of-business applications and login scripts often depend on a drive letter or UNC path such as S:\Projects. SharePoint does not expose libraries as SMB shares. Microsoft's supported way to work with SharePoint files in File Explorer is the OneDrive sync app, which places synced libraries in a folder under the organization's name.

The older View in File Explorer option, which relies on WebDAV, is hidden by default and Microsoft no longer recommends it. Microsoft also recommends syncing no more than 300,000 files across all synced libraries. Products that present SharePoint as a mapped drive do exist, MyWorkDrive among them, but they are an added layer to deploy. See our guide to mapping SharePoint as a network drive for the options and their trade-offs.

File size stopped being the main constraint when Microsoft raised the upload limit to 250 GB per file. The limits that catch file server migrations today are structural. The full decoded path, folders plus file name, can't exceed 400 characters, and deep folder trees copied from file shares often do.

A library can hold 30 million items, but views are throttled above 5,000 items. Microsoft supports up to 50,000 unique permissions per list or library and recommends staying under 5,000, while a file share with years of per-folder ACLs can exceed that. Once a library or folder holds more than 100,000 items, you can no longer break permission inheritance on it. The table above lists the limits that matter most, and our post on SharePoint storage limitations covers them in more depth.

Microsoft's SharePoint Migration Tool and Migration Manager can carry file share permissions across, so they don't have to be rebuilt by hand. The translation is lossy. Only Read, Write and Full Control map to SharePoint roles. Special permissions such as Deny are not saved, and Microsoft's migration guide warns that content previously protected by an explicit deny may become accessible. Users also have to be pre-provisioned in Microsoft 365 before their permissions can be mapped.

Any over-broad access you carry over gets easier to find once Microsoft 365 Copilot is deployed, because Copilot surfaces content to anyone with at least view permission. Microsoft publishes a Copilot oversharing blueprint for this reason, and we cover the issue in Microsoft 365 Copilot oversharing.

File names cause less trouble than they used to. SharePoint in Microsoft 365 blocks largely the same characters Windows already blocks (" * : < > ? / \ |), and # and % are now allowed. Leading and trailing spaces and reserved names such as .lock, desktop.ini and _vti_ still have to be fixed before migration.

SharePoint Online keeps deleted items for 93 days across its two recycle bin stages. Microsoft retains backups for another 14 days, which an administrator can request through support. That window covers accidental deletion.

Longer retention means adding Microsoft 365 Backup, priced at $0.15 per GB per month of protected content, retention policies in Microsoft Purview, or a third-party backup service. File shares fit into the backup and replication tooling you already run, and Windows Volume Shadow Copies let users restore previous versions themselves.

SharePoint storage is pooled per tenant: 1 TB plus 10 GB for each licensed user. Above the pool, Microsoft sells Office 365 Extra File Storage at a list price of about $0.20 per GB per month, and the first-stage recycle bin counts against the same pool.

A worked example: a 200-user organization gets 1 TB plus 2,000 GB, about 3 TB in total. Moving a 10 TB file server into SharePoint means buying roughly 7,200 GB of extra storage, about $1,440 per month, before counting what Teams and existing sites already use. Protecting that 10 TB with Microsoft 365 Backup adds about $1,536 per month. Keeping the data on existing storage avoids both charges, and Azure Files standard tiers bill at a fraction of the SharePoint rate. Training, support and SharePoint migration costs come on top.

Moving file shares into SharePoint places the data in Microsoft's cloud, in the geography assigned to your tenant, under Microsoft's terms. Many organizations accept that after a compliance and legal review. Others can't, because contracts or national rules require certain data to stay in a specific country or on infrastructure the organization controls.

US-headquartered cloud providers are also subject to the US CLOUD Act, which allows US authorities to compel production of data in a provider's custody, including data stored outside the United States. Our data sovereignty page explains how MyWorkDrive gives access to files that must stay where they are.

Files in SharePoint can be downloaded in their original formats. The structure around them is harder to bring back. SharePoint permissions, sharing links, version history and metadata columns have no direct NTFS equivalent.

Microsoft's migration tools are built to move content into Microsoft 365. Moving back to SMB shares, to Azure Files or to another vendor means a second project with third-party tools.

Multi-user desktop databases read and lock parts of a shared file over SMB while several people work in it. OneDrive syncs whole files between copies, so two people working in the same database can end up with separate copies. Microsoft's guidance for Access says that although a database can be saved to OneDrive or a SharePoint library, you should avoid opening it from there, and recommends sharing a split database over a local network. Microsoft also does not support syncing Outlook PST files while they are open. Accounting and CAD vendors publish their own networking requirements, and they are worth checking before moving those files anywhere.

These files belong on a file server on the LAN. For remote users, the dependable route is the application's own client-server option or a remote desktop session. That applies to VPNs and to MyWorkDrive as well. MyWorkDrive's optional default block list includes QuickBooks, Access and PST files, and our knowledge base explains which file types are not suited to remote access.

File shares can be archived to whatever tier you choose, from tape to cloud object storage, and restored with standard tools years later. In SharePoint, Microsoft 365 Archive moves inactive sites or files to a cold tier inside SharePoint. It costs $0.05 per GB per month for archived content above the tenant's storage quota, and Microsoft dropped the reactivation fee for SharePoint content in 2025.

Archived content stays in Microsoft 365 and is billed through pay-as-you-go Azure billing, so long-term retention depends on keeping both the subscription and that billing arrangement in place.