Planning for an Azure File Sync (preview) deployment

Use Azure File Sync (preview) to centralize your organization's file shares in Azure Files, while keeping the flexibility, performance, and compatibility of an on-premises file server. Azure File Sync transforms Windows Server into a quick cache of your Azure file share. You can use any protocol that's available on Windows Server to access your data locally, including SMB, NFS, and FTPS. You can have as many caches as you need across the world.

This article describes important considerations for an Azure File Sync deployment. We recommend that you also read Planning for an Azure Files deployment.

Azure File Sync terminology

Before getting into the details of planning for an Azure File Sync deployment, it's important to understand the terminology.

Storage Sync Service

The Storage Sync Service is the top-level Azure resource for Azure File Sync. The Storage Sync Service resource is a peer of the storage account resource, and can similarly be deployed to Azure resource groups. A distinct top-level resource from the storage account resource is required because the Storage Sync Service can create sync relationships with multiple storage accounts via multiple sync groups. A subscription can have multiple Storage Sync Service resources deployed.

Sync group

A sync group defines the sync topology for a set of files. Endpoints within a sync group are kept in sync with each other. If, for example, you have two distinct sets of files that you want to manage with Azure File Sync, you would create two sync groups and add different endpoints to each sync group. A Storage Sync Service can host as many sync groups as you need.

Registered server

The registered server object represents a trust relationship between your server (or cluster) and the Storage Sync Service. You can register as many servers to a Storage Sync Service instance as you want. However, a server (or cluster) can be registered with only one Storage Sync Service at a time.

Azure File Sync agent

The Azure File Sync agent is a downloadable package that enables Windows Server to be synced with an Azure file share. The Azure File Sync agent has three main components:

  • FileSyncSvc.exe: The background Windows service that is responsible for monitoring changes on server endpoints, and for initiating sync sessions to Azure.
  • StorageSync.sys: The Azure File Sync file system filter, which is responsible for tiering files to Azure Files (when cloud tiering is enabled).
  • PowerShell management cmdlets: PowerShell cmdlets that you use to interact with the Microsoft.StorageSync Azure resource provider. You can find these at the following (default) locations:
    • C:\Program Files\Azure\StorageSyncAgent\StorageSync.Management.PowerShell.Cmdlets.dll
    • C:\Program Files\Azure\StorageSyncAgent\StorageSync.Management.ServerCmdlets.dll

Server endpoint

A server endpoint represents a specific location on a registered server, such as a folder on a server volume. Multiple server endpoints can exist on the same volume if their namespaces do not overlap (for example, F:\sync1 and F:\sync2). You can configure cloud tiering policies individually for each server endpoint. Currently, it is not possible to create a server endpoint for the root of a volume (for example F:\ or C:\myvolume, if a volume is mounted as a mount point).


A server endpoint may be located on the Windows system volume. Cloud tiering is not supported on the system volume.

If you add a server location that has an existing set of files as a server endpoint to a sync group, those files are merged with any other files that are already on other endpoints in the sync group.

Cloud endpoint

A cloud endpoint is an Azure file share that is part of a sync group. The entire Azure file share syncs, and an Azure file share can be a member of only one cloud endpoint. Therefore, an Azure file share can be a member of only one sync group. If you add an Azure file share that has an existing set of files as a cloud endpoint to a sync group, the existing files are merged with any other files that are already on other endpoints in the sync group.


Azure File Sync supports making changes to the Azure file share directly. However, any changes made on the Azure file share first need to be discovered by an Azure File Sync change detection job. A change detection job is initiated for a cloud endpoint only once every 24 hours. In addition, changes made to an Azure file share over the REST protocol will not update the SMB last modified time and will not be seen as a change by sync. For more information, see Azure Files frequently asked questions.

Cloud tiering

Cloud tiering is an optional feature of Azure File Sync in which infrequently used or accessed files greater than 64 KiB in size can be tiered to Azure Files. When a file is tiered, the Azure File Sync file system filter (StorageSync.sys) replaces the file locally with a pointer, or reparse point. The reparse point represents a URL to the file in Azure Files. A tiered file has the "offline" attribute set in NTFS so third-party applications can identify tiered files. When a user opens a tiered file, Azure File Sync seamlessly recalls the file data from Azure Files without the user needing to know that the file is not stored locally on the system. This functionality is also known as Hierarchical Storage Management (HSM).


Cloud tiering is not supported for server endpoints on the Windows system volumes.

Azure File Sync interoperability

This section covers Azure File Sync interoperability with Windows Server features and roles and third-party solutions.

Supported versions of Windows Server

Currently, the supported versions of Windows Server by Azure File Sync are:

Version Supported SKUs Supported deployment options
Windows Server 2016 Datacenter and Standard Full (server with a UI)
Windows Server 2012 R2 Datacenter and Standard Full (server with a UI)

Future versions of Windows Server will be added as they are released. Earlier versions of Windows might be added based on user feedback.


We recommend keeping all servers that you use with Azure File Sync up to date with the latest updates from Windows Update.

File system features

Feature Support status Notes
Access control lists (ACLs) Fully supported Windows ACLs are preserved by Azure File Sync, and are enforced by Windows Server on server endpoints. Windows ACLs are not (yet) supported by Azure Files if files are accessed directly in the cloud.
Hard links Skipped
Symbolic links Skipped
Mount points Partially supported Mount points might be the root of a server endpoint, but they are skipped if they are contained in a server endpoint's namespace.
Junctions Skipped For example, Distributed File System DfrsrPrivate and DFSRoots folders.
Reparse points Skipped
NTFS compression Fully supported
Sparse files Fully supported Sparse files sync (are not blocked), but they sync to the cloud as a full file. If the file contents change in the cloud (or on another server), the file is no longer sparse when the change is downloaded.
Alternate Data Streams (ADS) Preserved, but not synced


Only NTFS volumes are supported. ReFS, FAT, FAT32, and other file systems are not supported.

Failover Clustering

Windows Server Failover Clustering is supported by Azure File Sync for the "File Server for general use" deployment option. Failover Clustering is not supported on "Scale-Out File Server for application data" (SOFS) or on Clustered Shared Volumes (CSVs).


The Azure File Sync agent must be installed on every node in a Failover Cluster for sync to work correctly.

Data Deduplication

For volumes that don't have cloud tiering enabled, Azure File Sync supports Windows Server Data Deduplication being enabled on the volume. Currently, we do not support interoperability between Azure File Sync with cloud tiering enabled and Data Deduplication.

Distributed File System (DFS)

Azure File Sync supports interop with DFS Namespaces (DFS-N) and DFS Replication (DFS-R) starting with Azure File Sync agent 1.2.

DFS Namespaces (DFS-N): Azure File Sync is fully supported on DFS-N servers. You can install the Azure File Sync agent on one or more DFS-N members to sync data between the server endpoints and the cloud endpoint. For more information, see DFS Namespaces overview.

DFS Replication (DFS-R): Since DFS-R and Azure File Sync are both replication solutions, in most cases, we recommend replacing DFS-R with Azure File Sync. There are however several scenarios where you would want to use DFS-R and Azure File Sync together:

  • You are migrating from a DFS-R deployment to an Azure File Sync deployment. For more information, see Migrate a DFS Replication (DFS-R) deployment to Azure File Sync.
  • Not every on-premises server which needs a copy of your file data can be connected directly to the internet.
  • Branch servers consolidate data onto a single hub server, for which you would like to use Azure File Sync.

For Azure File Sync and DFS-R to work side-by-side:

  1. Azure File Sync cloud tiering must be disabled on volumes with DFS-R replicated folders.
  2. Server endpoints should not be configured on DFS-R read-only replication folders.

For more information, see DFS Replication overview.

Antivirus solutions

Because antivirus works by scanning files for known malicious code, an antivirus product might cause the recall of tiered files. Because tiered files have the "offline" attribute set, we recommend consulting with your software vendor to learn how to configure their solution to skip reading offline files.

The following solutions are known to support skipping offline files:

Backup solutions

Like antivirus solutions, backup solutions might cause the recall of tiered files. We recommend using a cloud backup solution to back up the Azure file share instead of an on-premises backup product.

Encryption solutions

Support for encryption solutions depends on how they are implemented. Azure File Sync is known to work with:

  • BitLocker encryption
  • Azure Rights Management Services (Azure RMS) (and legacy Active Directory RMS)

Azure File Sync is known not to work with:

  • NTFS Encrypted File System (EFS)

In general, Azure File Sync should support interoperability with encryption solutions that sit below the file system, such as BitLocker, and with solutions that are implemented in the file format, such as BitLocker. No special interoperability has been made for solutions that sit above the file system (like NTFS EFS).

Other Hierarchical Storage Management (HSM) solutions

No other HSM solutions should be used with Azure File Sync.

Region availability

Azure File Sync is available only in the following regions in preview:

Region Datacenter location
East US Virginia, USA
West US California, USA
West Europe Netherlands
South East Asia Singapore
Australia East New South Wales, Australia

In preview, we support syncing only with an Azure file share that's in the same region as the Storage Sync Service.

Azure File Sync agent update policy

Updates to the Azure File Sync agent will be released on a regular basis to add new functionality, and to address any issues that were discovered. We recommend that you configure Microsoft Update to get all updates to the Azure File Sync agent as we release them. We understand that some organizations like to strictly control and test updates.

For deployments that use earlier versions of the Azure File Sync agent:

  • The Storage Sync Service honors the preceding major version for three months after the initial release of a new major version. For example, the Storage Sync Service would support version 1.* until three months after the release of version 2.*.
  • After three months have elapsed, the Storage Sync Service begins to block Registered Servers that are using the expired version from syncing with their Sync Groups.
  • Within the three months for a preceding major version, all bug fixes go only to the current major version.


We will notify you via toast notification in the Azure portal if you are using a version of Azure File Sync that will expire within the next three months.

Next steps