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).


Only non-removable volumes are supported. Drives mapped from a remote share are not supported for a server endpoint path. In addition, a server endpoint may be located on the Windows system volume though 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 For example, classification tags created by the File Classification Infrastructure are not synced. Existing classification tags on files on each of the server endpoints are left untouched.


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 Information Protection, Azure Rights Management Services (Azure RMS), and 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
Australia East New South Wales
Canada Central Toronto
East US Virginia
Southeast Asia Singapore
UK South London
West Europe Netherlands
West US California

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

The Azure File Sync agent is updated on a regular basis to add new functionality and to address issues. We recommend you configure Microsoft Update to get updates for the Azure File Sync agent as they're available.

Major vs. minor agent versions

  • Major agent versions often contain new features and have an increasing number as the first part of the version number. For example: *2.*.**
  • Minor agent versions are also called "patches" and are released more frequently than major versions. They often contain bug fixes and smaller improvements but no new features. For example: **.3.**

Upgrade paths

There are three approved and tested ways to install the Azure File Sync agent updates. These update paths work for both major and minor versions.

  1. (Preferred) Configure Microsoft Update to automatically download and install agent updates.
    We always recommend taking every Azure File Sync update to ensure you have access to the latest fixes for the server agent. Microsoft Update makes this process seamless, by automatically downloading and installing updates for you.
  2. Patch an existing Azure File Sync agent by using a Microsoft Update patch file, or a .msp executable. The latest Azure File Sync update package can be downloaded from the Microsoft Update Catalog.
    Running a .msp executable will upgrade your Azure File Sync installation with the same method used automatically by Microsoft Update in the previous upgrade path. Applying a Microsoft Update patch will perform an in-place upgrade of an Azure File Sync installation.
  3. Download the newest Azure File Sync agent installer from the Microsoft Download Center. The installer download is a Microsoft Installer package, or a .msi executable.
    To upgrade an existing Azure File Sync agent installation, uninstalled the older version and then install the latest version from the downloaded installer. The server registration, sync groups, and any other settings are maintained by the Azure File Sync installer.

Agent lifecycle and change management guarantees

Azure File Sync is a cloud service, which enables continuously introduction of new features and functionality. This means that a specific Azure File Sync agent version can only be supported for a limited time. To facilitate your deployment, the following rules to guarantee you have enough time and notification to accommodate agent updates/upgrades in your change management process:

  • Major agent versions are supported for at least six months from the date of initial release.
  • We guarantee there is an overlap of at least three months between the support of major agent versions.
  • Warnings are issued for registered servers using a soon-to-be expired agent at least three months prior to expiration. You can check if a registered server is using an older version of the agent under the registered servers section of a Storage Sync Service.
  • The lifetime of a minor agent version is bound to the associated major version. For example, when agent version 3.0 is released, agent versions 2.* will all be set to expire together.


Installing an agent version with an expiration warning will display a warning but succeed. Attempting to install or connect with an expired agent version is not supported and will be blocked.

Next steps