What a file server migration to SharePoint Online involves
A network share has been accumulating folders since the company bought its first server, and the request to move it to SharePoint Online usually arrives as a storage question. EPC Group answers it as a structure question. The copy itself is the smallest part of the work; the parts that decide whether users adopt the result are the decisions about where content goes, who can see it, and how it is found. Microsoft describes the migration in five phases: planning, assessing and remediating content, preparing the OneDrive and SharePoint environment, migrating, and onboarding users (Microsoft Learn, Guide to migrating file shares to OneDrive, Teams, and SharePoint, accessed 2026-10-20). EPC Group's SharePoint migration practice follows the same five phases and spends the most time in the first two.
Why information architecture comes first
A file server is a single tree. SharePoint Online is a set of sites, each with its own libraries and permissions, connected by hubs and search. If the tree is copied as-is into one library, the new environment inherits every ambiguity of the old one, and some limits bite: Microsoft caps lists and libraries at 2,000 per site collection, and once a library or folder exceeds 100,000 items, permission inheritance on it can no longer be broken or re-inherited (Microsoft Learn, SharePoint limits, accessed 2026-10-20). Microsoft also asks the architecture question directly: content a single user owns belongs in that person's OneDrive, and content a team works on belongs in a shared library where team members have default access (Microsoft Learn, Guide to migrating file shares to OneDrive, Teams, and SharePoint, accessed 2026-10-20). EPC Group therefore maps each top-level share to a site or to OneDrive before any tool runs, decides which second-level folders become separate libraries, and identifies the content that should not move at all because it is redundant or out of date, which Microsoft lists as an explicit planning question (same source).
The assessment and what it finds
The SharePoint Migration Tool scans files and produces assessment reports, and Microsoft recommends running it with the setting to only perform scanning before any migration starts (Microsoft Learn, Guide to migrating file shares to OneDrive, Teams, and SharePoint, accessed 2026-10-20). EPC Group reads three reports closely. Path length: the entire decoded file path including the file name cannot exceed 400 characters in SharePoint and OneDrive (Microsoft Learn, SharePoint limits, accessed 2026-10-20), and deep folder trees from a decade of departmental habits exceed it routinely. Characters and file types: names containing invalid characters must be substituted, the # and % characters are supported but not enabled by default, and scripting file types are blocked by default because custom script is turned off in OneDrive (Microsoft Learn, Guide to migrating file shares to OneDrive, Teams, and SharePoint, accessed 2026-10-20). Content that will not move: Microsoft lists embedded URL conversion, Windows hidden attributes, explicit deny permissions, inaccessible or corrupted documents, and files or folders exceeding SharePoint restrictions as not migrated (same source). Each finding becomes a remediation task with an owner before the pilot.
The permission model changes, and that is the point
NTFS permissions do not survive the move intact, and EPC Group treats that as an opportunity rather than a loss. Microsoft documents the translation: Full control maps to Full control, Modify and Write map to the SharePoint Contribute role, and Read, Read and execute, and List folder contents map to Read. The most restrictive of the share permission and the NTFS permission sets the final level, all advanced NTFS permissions are removed, and explicit deny permissions are not migrated, which means content protected only by a deny may become accessible (Microsoft Learn, Guide to migrating file shares to OneDrive, Teams, and SharePoint, accessed 2026-10-20). Rather than reproduce thousands of per-folder grants, EPC Group designs permissions at the site and library level using groups, keeps unique permissions well under the 5,000 per list or library that Microsoft recommends as a general limit (Microsoft Learn, SharePoint limits, accessed 2026-10-20), and audits every deny on the source so that the content behind it is moved to a restricted site instead.
SharePoint Migration Tool, Migration Manager, or a third-party tool
Microsoft provides two tools and describes a third lane. The SharePoint Migration Tool is a free solution that migrates file shares and SharePoint Server 2010, 2013, 2016 and 2019 content to SharePoint, OneDrive and Teams, supports a scan-only mode, and exposes all functionality in PowerShell (Microsoft Learn, Overview of the SharePoint Migration Tool (SPMT), accessed 2026-10-20). It also supports incremental migration, so a task can be rerun to copy only new or updated files, and offers separate settings for file share permissions and version history (Microsoft Learn, SPMT-supported features, accessed 2026-10-20). Migration Manager lives in the SharePoint admin center; it lets you set up multiple computers or virtual machines as agents, assigns tasks to the next available agent, groups agents for performance, runs prescans, accepts a CSV for bulk tasks, requires SMB 2.0 or higher on the source, and supports files up to 250 GB (Microsoft Learn, Overview: Migrate your file shares to Microsoft 365, accessed 2026-10-20). Each agent can hold up to 10 tasks in its queue (Microsoft Learn, Step 2: Create a migration task with Migration Manager, accessed 2026-10-20). Microsoft's guide then lists a partner-driven option, customized to need with expertise provided (Microsoft Learn, Guide to migrating file shares to OneDrive, Teams, and SharePoint, accessed 2026-10-20); commercial products such as ShareGate sit in that lane. EPC Group's rule: the SharePoint Migration Tool for a handful of shares, Migration Manager when scale or parallel agents are needed, and a third-party tool only when the requirement list exceeds what the two Microsoft tools document.
What users notice after cutover
Microsoft recommends an incremental migration that runs in the background with no user impact, followed by a cutover event in which the network and local file shares are disabled and users are directed to SharePoint or OneDrive; it recommends a single cutover for all users to prevent people from updating duplicate copies (Microsoft Learn, Guide to migrating file shares to OneDrive, Teams, and SharePoint, accessed 2026-10-20). What users notice first is the absence of a drive letter. EPC Group replaces mapped drives with OneDrive sync of the libraries each role needs, mindful that Microsoft recommends syncing no more than 300,000 files in a single library or across all synced libraries for performance (Microsoft Learn, SharePoint limits, accessed 2026-10-20). The onboarding plan Microsoft describes covers the reasons for the move, end-user training, help desk training before cutover, and clear communication of timing and impact (Microsoft Learn, Guide to migrating file shares to OneDrive, Teams, and SharePoint, accessed 2026-10-20). EPC Group's SharePoint consulting practice adds department champions, a read-only period on the old share, and a hypercare window before the share is retired.
Documented work
ANON-CASES: EPC Group engagement data for file share migration covers mid-size commercial organizations retiring on-premises file servers in favor of SharePoint Online and OneDrive, delivered by the firm's SharePoint migration practice. Client names are not published here. Engagements are described by sector and organization size only, and no outcome figures are quoted that cannot be traced to a signed deliverable. EPC Group is a Microsoft Solutions Partner with all six Solutions Partner Designations as of October 2026.
Primary sources
- Overview: Migrate your file shares to Microsoft 365 — Microsoft Learn, accessed 2026-10-20
- SharePoint limits — Microsoft Learn, accessed 2026-10-20
- Step 2: Create a migration task with Migration Manager — Microsoft Learn, accessed 2026-10-20
Frequently Asked Questions
Why does information architecture come before migration?
Because a file share is one tree and SharePoint is many sites, and the tooling copies whatever structure you give it. Microsoft advises deciding what content goes where before migrating: files owned by one person belong in OneDrive, files a team works on belong in a shared library (Microsoft Learn, Guide to migrating file shares to OneDrive, Teams, and SharePoint, accessed 2026-10-20). EPC Group designs sites, libraries and permission groups first so the migration lands content in a structure that survives the next reorganization.
How are permissions translated from NTFS to SharePoint?
Microsoft documents the mapping: Full control becomes Full control, Modify and Write become Contribute, and Read, Read and execute, and List folder contents become Read. The most restrictive of the share permission and the NTFS permission determines the final level, all advanced NTFS permissions are removed, and explicit deny permissions are not migrated, so content under a deny may become accessible (Microsoft Learn, Guide to migrating file shares to OneDrive, Teams, and SharePoint, accessed 2026-10-20). EPC Group replaces item-level grants with group-based site permissions.
Which migration tools exist (Microsoft SharePoint Migration Tool, Migration Manager, third-party) and how do they differ?
The SharePoint Migration Tool is a free desktop tool that moves file shares and SharePoint Server 2010 through 2019 content to SharePoint, OneDrive and Teams, with a scan-only mode and PowerShell support (Microsoft Learn, Overview of the SharePoint Migration Tool (SPMT), accessed 2026-10-20). Migration Manager runs in the SharePoint admin center, distributes tasks across multiple agent computers, and supports files up to 250 GB (Microsoft Learn, Overview: Migrate your file shares to Microsoft 365, accessed 2026-10-20). Third-party tools fill the partner-driven lane Microsoft describes for customized needs.
What breaks: long paths, special characters, mapped drives, Access databases?
The decoded file path including the file name cannot exceed 400 characters in SharePoint and OneDrive (Microsoft Learn, SharePoint limits, accessed 2026-10-20). Invalid characters in file and folder names must be substituted before migration, and the # and % characters are supported but not enabled by default (Microsoft Learn, Guide to migrating file shares to OneDrive, Teams, and SharePoint, accessed 2026-10-20). Mapped drive letters disappear and are replaced by OneDrive sync or browser access. EPC Group treats shared multi-user Access databases as application dependencies and handles them on a separate track rather than copying them into a library.
How is adoption handled after cutover?
Microsoft recommends an onboarding plan that explains the reasons for the move, trains end users on OneDrive, trains the help desk before the cutover event, and sends communications with timelines and expected impact; it also recommends a single cutover event for all users so that nobody keeps updating duplicate copies (Microsoft Learn, Guide to migrating file shares to OneDrive, Teams, and SharePoint, accessed 2026-10-20). EPC Group adds a two-week hypercare window, read-only access to the old share, and a short list of champions per department who answer the first-week questions.
Talk to a senior architect
If your organization is planning to retire a file server, a 30-minute discovery call with a senior EPC Group architect will cover the share-to-site map, the assessment scan and the tool choice. See the SharePoint consulting service hub for engagement structures.
Email contact@epcgroup.net or call 888-381-9725.
a Microsoft Gold Partner (2000 until Microsoft retired the program in 2022) — today holding all six Microsoft Solutions Partner Designations.
Documented engagements
Each record publishes a redacted primary-source document — a client purchase order, executed agreement or payment record — with a SHA-256 hash you can recompute, and states what the document does not establish.
- Canadian Forces Morale & Welfare Services — Contracted
- Federal Reserve Bank of New York — Contracted — countersigned
- National Institutes of Health — Work-product evidenced
- NASA Johnson Space Center — Contracted
- Stryker — Delivered — payment-corroborated (client payment records published)
- Novartis — Contracted — countersigned
- Samsung Semiconductor — Contracted — countersigned
- Haskell — Contracted — countersigned
- PepsiCo — EPC-executed instrument + work product
- YMCA Houston — Work-product evidenced
- Georgia Tech — Contracted