Migration Overview for SMB Azure File Shares

Migrate to SMB Azure file shares — Summary

Purpose

• Overview of considerations and guidance for migrating SMB file shares to Azure file shares (SMB). Guides are organized by source location and target deployment model (hybrid with Azure File Sync or cloud-only).

Applies to

• SMB file shares supported: Standard (GPv2) and Premium (FileStorage) with LRS/ZRS/GRS/GZRS as listed. NFS not supported for these SMB file share types.

Migration basics

• Goal: move existing file share data into native Azure file shares while preserving data integrity and minimizing downtime.

• Azure options:

  • Azure file shares: best for general-purpose SMB file data; can be cached on Windows Servers with Azure File Sync.

  • Azure Disks: option when apps are moved to VMs and need machine-local shared disks.

  • Azure blobs: better for apps that do not require SMB semantics.

• Choose the Azure storage type that matches your performance and fidelity needs.

Preserving file fidelity

• File fidelity = ability to preserve file data stream and file metadata through discovery, copy, and storage on target.

• File components:

  • Data stream (file content).

  • File metadata: attributes, NTFS permissions (owner SID, group SID, DACLs, SACLs), timestamps (creation, last-modified), alternate data streams (ADS).

• Notes:

  • ADS cannot be stored in Azure file shares (they’re preserved only when using Azure File Sync on-premises).

  • LastAccessTime timestamp isn’t supported on target; LastModifiedTime isn’t updated on read and can equal CreationTime.

  • Important: set root directory ACLs on the target share before copying large data sets to avoid long propagation delays.

  • AD DS or Microsoft Entra Domain Services identities can be used for identity-based authentication to Azure Files.

Supported metadata (what can be preserved)

• Directory structure: preserved.

• Access permissions: Azure Files supports Windows ACLs and can preserve owner SID, group SID, DACLs, SACLs.

• Create, change, modified timestamps: preservable (except LastAccessTime limitation noted above).

• File attributes (read-only, hidden, archive): preservable.

Migration phases

• Discovery

  • Inventory all SMB shares to migrate (size, count, dependencies). For >100 TiB consider Komprise for discovery and analysis.

  • Sources may include Windows servers, Linux servers, cloud, or NAS devices.

• Assessment

  • Decide storage target, deploy Azure resources, and prepare Azure usage.

  • Deploy storage accounts and file shares:

    • Standard storage accounts pool IOPS/throughput across shares.

    • For highly active shares, use separate storage accounts; premium FileStorage accounts provide dedicated performance per share.

    • Map shares to storage accounts and use meaningful names.

    • Note: 250 storage accounts per subscription per region limit.

  • Prepare for usage:

    • Networking: choose public endpoints, private endpoints, or both; enable SMB routing.

    • Authentication: configure identity-based auth and join storage account to AD domain if needed.

    • Authorization: set share-level ACLs; NTFS ACLs apply within shares.

    • Business continuity: consider DFS Namespaces to preserve existing share addresses and redirect clients.

How to use the migration guide table

1

Locate the row for your current source system.

2

Choose a target:

• Hybrid deployment: Azure Files + Azure File Sync (cache on-premises or in Azure).

• Cloud-only deployment: Azure Files in the cloud without on-premises caching.

3

In the intersecting cell for your source and chosen target, pick the migration scenario and follow the linked guide.

Migration guides (high-level)

• Windows Server 2012 R2+: Hybrid — Azure File Sync (or DataBox + Azure File Sync). Cloud-only — Azure File Sync then decommission server endpoint, or RoboCopy to mounted Azure file share.

• Windows Server 2012 and earlier: Use DataBox or Storage Migration Service to an updated server with Azure File Sync; RoboCopy to mounted share for cloud-only.

• NAS: Hybrid — Azure File Sync upload, or DataBox + Azure File Sync. Cloud-only — DataBox or RoboCopy to mounted Azure file share.

File-copy tools — guidance and recommendations

• Consider whether a tool:

  • Supports source and target locations,

  • Supports available protocols (SMB, REST),

  • Preserves needed file fidelity,

  • Fits migration strategy (e.g., supports mirroring to reduce downtime).

• Recommended tools (preserve full fidelity where noted):

  • Azure Data Box: supported, full fidelity.

  • RoboCopy: supported (mount Azure file share), full fidelity.

  • Azure File Sync: native integration, full fidelity.

  • Storage Migration Service: indirectly supported via mounting shares on target server, full fidelity.

  • Data Box (with copy service): supports metadata; Data Box Disks does not preserve metadata.

• Not fully recommended:

  • AzCopy: supported but limited (uses REST APIs, may lose some fidelity); supports up to 10M files per job.

  • Azure Storage Explorer: supported but loses most fidelity (ACLs), preserves timestamps.

• Not recommended:

  • Azure Data Factory: supported but doesn’t copy metadata.

Migration helper tools

• RoboCopy: built into Windows; useful for SMB migrations (many options).

• TreeSize (JAM Software): helps estimate number of items (files/folders) — useful because Azure File Sync scales primarily by item count. Tested version 4.4.1; compatible with cloud-tiered files and doesn’t cause recalls during normal operation.

Key links (for details)

• Azure file share overview

• Azure File Sync planning and cloud tiering

• Create an SMB file share

• Azure Files networking overview

• Identity-based authentication for Azure Files

• DataBox and Storage Migration Service pages (Links in the original article provide step-by-step migration guides and tool documentation.)

Important reminders

• Set root ACLs on the target share before large migrations.

• ADS are not stored in Azure file shares (use Azure File Sync to preserve on-premises).

• LastAccessTime isn’t supported on target; LastModifiedTime won’t change on reads.

Last updated

• 09/02/2025

If you want, I can produce:

• A compact checklist for a migration project,

• A one-page decision flow to pick tools based on source and scale,

• Or expand any section into step-by-step actions with links to the specific migration guides.