Windows File Server to NAS Migration Guide

Replacing an aging Windows file server with a NAS is one of the most common SMB IT projects. A dedicated NAS costs less to run, requires less management overhead, and provides comparable SMB file sharing with built-in RAID for most workgroup environments. This guide covers migrating from a Windows Server (2016/2019/2022) to a Synology or QNAP NAS: inventorying existing shares and permissions, migrating data, recreating user accounts and share permissions on the NAS, and transitioning clients with minimal downtime. Both Synology DSM and QNAP QTS support Active Directory integration, SMB share permissions matching Windows Server, and all standard Windows client features (offline files, Distributed File System references).

Phase 1: Inventory the Existing Windows File Server

Before migrating, document what exists on the current server. Run the following on the Windows Server to export share and permission information:

net share > shares.txt
Get-SmbShare | Select-Object Name,Path,Description | Export-Csv shares.csv
Get-Acl -Path C:\Shares\* | Format-List | Out-File permissions.txt

Document for each share:

• Share name and UNC path (e.g. \\SERVER\Finance)
• Local path on server (e.g. D:\Shares\Finance)
• Users and groups with access, and their permission level (Read, Read/Write, Full Control)
• Approximate data size: Get-ChildItem -Path D:\Shares\ -Recurse | Measure-Object -Property Length -Sum

This inventory drives the NAS share structure and user account setup.

Phase 2: Set Up NAS Shares and User Accounts

On the NAS, recreate the share and user structure from your inventory:

Option A: Local NAS users (small workgroups without Active Directory):

1. Create a shared folder on the NAS for each Windows share (e.g. Finance, Projects)
2. Create user accounts matching your Windows Server user names (same username, new password. Distribute to users)
3. Assign each user to the appropriate shared folders with Read or Read/Write permissions in the NAS control panel

Option B: Active Directory domain join (workgroups with an AD domain):

1. On Synology: DSM → Control Panel → Domain/LDAP → Join domain. Enter domain controller details
2. On QNAP: QTS → Control Panel → Network and File Services → Win/Mac/NFS → Microsoft Networking → Security → Join domain
3. After joining, AD users and groups are available in the NAS share permission editor
4. Assign AD groups to NAS shared folders. The permission model mirrors Windows Server share permissions

AD domain join means users authenticate with their existing domain credentials. No new password distribution required. Strongly recommended if you already have an AD domain.

Phase 3: Migrate Data with Robocopy

Robocopy is the standard tool for migrating Windows file server data. Run from the Windows Server or a client with access to both source and destination:

robocopy "\\SERVER\Finance" "\\NAS-IP\Finance" \
  /E /COPYALL /DCOPY:T /R:3 /W:5 /LOG:migration_finance.log /TEE

Key flags:

• /E. Copy all subdirectories including empty ones
• /COPYALL. Copy file data, attributes, timestamps, and Windows ACLs. Note: NAS file systems (ext4, Btrfs) do not preserve Windows NTFS ACLs natively. Permissions must be set on the NAS share level, not individual files
• /DCOPY:T. Preserve directory timestamps
• /R:3 /W:5. 3 retries, 5 second wait (handles locked files)
• /LOG. Write log to file for audit trail

For large migrations: run an initial robocopy pass to copy the bulk of data (this can run overnight), then run a second pass with /XO (exclude older) to sync changes made since the first pass. The second pass runs quickly and minimises the cutover window.

Phase 4: Client Cutover

Transitioning clients from the Windows Server to the NAS can be done two ways:

DNS redirect (zero-client-change): Update the DNS A record for the old server name to point to the NAS IP. Clients using \\servername\share paths continue to work because the name resolves to the NAS. This requires the NAS to have the same SMB share names and the NAS hostname to match (or use a CNAME). Cleanest approach for large numbers of clients.

Group Policy mapped drives update: If clients have mapped drives assigned via Group Policy, update the GP drive mapping to point to the NAS UNC path. Push the GP update. Clients receive the new mapping at next logon or policy refresh.

Manual re-mapping (small environments): For 5-10 users, update each client's drive mappings manually. Right-click the mapped drive → Disconnect. Then Map Network Drive → enter the NAS path (\\NAS-IP\Finance). This takes 2-5 minutes per workstation.

After cutover, verify: users can read and write, permissions are correct for each group, and no users report access issues. Leave the Windows Server online for 1-2 weeks as a fallback before decommissioning.

Phase 5: Post-Migration Checklist

After the cutover:

• ✅ Verify all share permissions. Test with a standard user account (not admin)
• ✅ Confirm backup is running on the NAS (Hyper Backup or Hybrid Backup Sync)
• ✅ Update DNS records to reflect the new NAS as the file server
• ✅ Document the new share paths and share them with users
• ✅ Run a final robocopy sync to capture any files written to the old server after cutover
• ✅ Test restore from the NAS backup before decommissioning the Windows Server
• ✅ Decommission Windows Server or repurpose for other roles

🇦🇺 Australian Buyers: NAS Recommendations for SMB Migration

Recommended NAS for Windows file server replacement in Australian SMB environments (March 2026):

• Synology DS423+ (~$980): Most common SMB file server replacement. Active Backup for Business (backup Windows PCs agentless), strong AD integration, Hyper Backup for cloud offsite. Intel Celeron J4125 handles 10-20 simultaneous SMB connections comfortably
• Synology DS923+ (~$980): AMD Ryzen R1600. Stronger multi-threaded performance for environments with 20+ simultaneous users or heavy file operations. Same software suite
• QNAP TS-464 (~$989): Good alternative for environments that want hardware flexibility (PCIe 10GbE upgrade path). QTS Active Directory integration is mature. Hybrid Backup Sync handles cloud backup

For environments needing 10GbE for high-throughput file sharing (video production, large CAD files), consider Synology DS1823xs+ or QNAP TS-873A for built-in 10GbE, or add a PCIe 10GbE card to the TS-464.

See the small business NAS setup guide for a complete walkthrough of configuring a new NAS for SMB use, and the best NAS guide for broader model comparisons.

Use our free NAS vs Cloud Migration Cost Calculator to compare the total cost of migrating from cloud to your own NAS.