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--- title: Migrate Data into Azure File Sync with Azure Data Box description: Migrate bulk data offline that's compatible with Azure File Sync. Avoid file conflicts, and catch up your file share with the latest changes on the server for a zero downtime cloud migration. author: khdownie ms.service: azure-file-storage ms.topic: how-to ms.date: 08/12/2026 ms.author: kendownie # Customer intent: "As an IT administrator, I want to migrate bulk data from on-premises Windows Server to Azure File Sync using Azure Data Box, so that I can ensure zero downtime and keep my file shares updated with the latest changes during the migration process." --- # Migrate data offline to Azure File Sync with Azure Data Box :heavy_check_mark: **Applies to:** Classic SMB file shares created with the Microsoft.Storage resource provider :heavy_multiplication_x: **Doesn't apply to:** All NFS file shares including file shares created with the Microsoft.FileShares resource provider or classic file shares created with the Microsoft.Storage resource provider This article describes how to use Azure Data Box to bulk-migrate data from an on-premises Windows Server to Azure file shares, then set up Azure File Sync on the source server for ongoing synchronization. Check if this article applies to your scenario: :::row::: :::column::: :::image type="content" source="media/storage-files-migration-server-hybrid-databox/file-sync-data-box-concept.png" alt-text="A display of three sequential steps described in this migration guide. The column next to the image describes them in detail." lightbox="media/storage-files-migration-server-hybrid-databox/file-sync-data-box-concept-expanded.png"::: :::column-end::: :::column::: > [!div class="checklist"] > * Data source: Windows Server 2016 or newer where Azure File Sync will be installed and point to the original set of files. > * Migration route: Windows Server 2016 or newer &rArr; Data Box &rArr; Azure file share &rArr; sync with Windows Server original file location > * Caching files on-premises: Yes, the final goal is an Azure File Sync deployment that syncs the files from where they are now. :::column-end::: :::row-end::: Using Azure Data Box is a viable path to move the bulk of the data from your on-premises Windows Server to separate Azure file shares and then, optionally, add Azure File Sync on the original source server. There are different migration paths available to you. It's important to follow the right one: * Your data lives on a Windows Server 2016 or newer and you plan to install Azure File Sync on that server and sync the original location. In this scenario, you don't want to upload all files and use Data Box instead, then use file sync for ongoing changes. If this is your scenario, then this article describes your migration path. * You have data on a source where you can't or won't install Azure File Sync, such as a Network Attached Storage (NAS) device or a different server. Instead, create a new, empty server and use Azure File Sync on that server. If that is your scenario, then this isn't the right migration guide for you. Instead, see [Migrate from NAS via Data Box to Azure File Sync](storage-files-migration-nas-hybrid-databox.md) or find the best guide for your scenario on the [migration overview](storage-files-migration-overview.md) page. * For all other scenarios, check the [table of Azure file share migration guides](storage-files-migration-overview.md), which provides a good starting point for all migration scenarios. ## Migration overview The migration process consists of several phases. You need to: - Deploy storage accounts and file shares. - Deploy one or more Azure Data Box devices to move the data from your Windows Server 2016 or newer. - Configure Azure File Sync with authoritative upload. The following sections describe the phases of the migration process in detail. ## Phase 1: Determine how many Azure file shares you need With this migration guide, you must continue to use the on-premises direct attached storage (DAS) that contains your files. Data Box will be fed from that location and Azure File Sync will also be set up on that location. NAS (Network Attached Storage) does not work with this migration path. You determine what syncs by setting up Azure File Sync *sync groups* that each determine where a set of files syncs between. Each sync group has at least one server location, called a *server endpoint* and one Azure file share, called the *cloud endpoint*. You can sync sub paths of a set of files to each their own Azure file share. This setup means several sync groups to cover a set of files completely. The remainder of the section describes your options. If you need to restructure your data, do so before you continue with this guide, order a Data Box, or set up sync. > [!CAUTION] > Ensure your file and folder structure is how you want it to be long-term before you begin the migration. Avoid any unnecessary folder restructuring during the migration. This restructuring decreases the positive effects of using Azure Data Box for initial, bulk transport of files to Azure. [!INCLUDE [storage-files-migration-namespace-mapping](../../../includes/storage-files-migration-namespace-mapping.md)] ## Phase 2: Deploy Azure storage resources In this phase, consult the mapping table from Phase 1 and use it to provision the correct number of Azure storage accounts and file shares within them. [!INCLUDE [storage-files-migration-provision-azfs](../../../includes/storage-files-migration-provision-azure-file-share.md)] ## Phase 3: Determine how many Azure Data Box appliances you need Start this step only after you've finished the previous phase. Your Azure storage resources (storage accounts and file shares) should be created at this time. When you order your Data Box, you need to specify the storage accounts into which the Data Box is moving data. In this phase, map the results of the migration plan from the previous phase to the limits of the available Data Box options. These considerations help you make a plan for which Data Box options to choose and how many of them you need to move your server shares to Azure file shares. To determine how many devices you need and their types, consider these important limits: * Any Azure Data Box appliance can move data into up to 10 storage accounts. * Each Data Box option comes with its own usable capacity. See [Data Box options](#data-box-options). Consult your migration plan to find the number of storage accounts you decide to create and the shares in each one. Then look at the size of each of the shares on your server. Combining this information allows you to optimize and decide which appliance should send data to which storage accounts. Two Data Box devices can move files into the same storage account, but don't split content of a single file share across two Data Boxes. ### Data Box options For a standard migration, choose one or a combination of these Data Box options: | Option | Description | Usable capacity | More information | |---|---|---|---| | **Data Box Disk** | Microsoft sends you between one and five SSD disks that each have a capacity of 8 TiB, for a maximum total of 40 TiB. | About 20% less than raw capacity due to encryption and file-system overhead. | [Data Box Disk documentation](../../databox/data-box-disk-overview.md) | | **Data Box** | The most common option. Microsoft sends you a ruggedized appliance that works similarly to a NAS. | 80, 120, or 525 TiB depending on SKU. | [Data Box documentation](../../databox/data-box-overview.md?pivots=dbx-ng) | | **Data Box Heavy** | A ruggedized appliance on wheels that works similarly to a NAS. | 1 PiB (about 20% less usable due to encryption and file-system overhead). | [Data Box Heavy documentation](../../databox/data-box-heavy-overview.md) | > [!NOTE] > For Data Box and Data Box Heavy, only copying data via SMB is supported. Copying data via the data copy service isn't supported because it doesn't preserve file fidelity. ## Phase 4: Copy files onto your Data Box When your Data Box arrives, set it up with unimpeded network connectivity to your Windows Server. Follow the setup documentation for the type of Data Box you ordered: * [Set up Data Box](../../databox/data-box-quickstart-portal.md). * [Set up Data Box Disk](../../databox/data-box-disk-quickstart-portal.md). * [Set up Data Box Heavy](../../databox/data-box-heavy-quickstart-portal.md). Depending on the type of Data Box, Data Box copy tools might be available. These tools aren't recommended for migrations to Azure file shares because they don't copy your files to the Data Box with full fidelity. Use Robocopy instead. When your Data Box arrives, it will have pre-provisioned SMB shares available for each storage account you specified when you ordered it. * If your files go into an SSD Azure file share, there will be one SMB share per SSD "FileStorage" storage account. * If your files go into an HDD storage account, there are three SMB shares per HDD pay-as-you-go storage account. Only the file share that ends with `_AzFile` is relevant for your migration. Ignore any block and page blob shares. ### How Data Box maps folders to Azure file shares Under the `<storage-account-name>_AzFile` device share, each first-level folder maps to an Azure file share on the target storage account: - The first-level folder name becomes the Azure file share name during ingestion. If a share with that name doesn't already exist in the target storage account, Data Box creates it. If it does exist, Data Box copies the data into that existing share. - Don't copy files directly to the root of the `_AzFile` share. All data must go inside a first-level folder. - For a one-to-one mapping with your source SMB shares, create one first-level folder for each source share (using the desired Azure file share name) and copy each source share into its corresponding folder. For example: ``` \\<DataBox-IP>\<storage-account-name>_AzFile\Share1 \\<DataBox-IP>\<storage-account-name>_AzFile\Share2 \\<DataBox-IP>\<storage-account-name>_AzFile\Share3 ``` For more information, see [Connect to Data Box](../../databox/data-box-deploy-copy-data.md#connect-to-data-box). Follow the steps in the Azure Data Box documentation: 1. [Connect to Data Box](../../databox/data-box-deploy-copy-data.md). 1. Copy data to Data Box. 1. [Prepare your Data Box for upload to Azure](../../databox/data-box-deploy-picked-up.md). The linked Data Box documentation specifies a Robocopy command. That command isn't suitable for preserving the full file and folder fidelity. Use this command instead: [!INCLUDE [storage-files-migration-robocopy](../../../includes/storage-files-migration-robocopy.md)] ## Phase 5: Deploy the Azure File Sync cloud resource Before you continue with this guide, wait until all of your files have arrived in the correct Azure file shares. The process of shipping and ingesting Data Box data will take time. [!INCLUDE [storage-files-migration-deploy-afs-sss](../../../includes/storage-files-migration-deploy-azure-file-sync-storage-sync-service.md)] ## Phase 6: Deploy the Azure File Sync agent [!INCLUDE [storage-files-migration-deploy-afs-agent](../../../includes/storage-files-migration-deploy-azure-file-sync-agent.md)] ## Phase 7: Configure Azure File Sync on the existing Windows Server Your registered on-premises Windows Server instance must be ready and connected to the internet for this process. [!INCLUDE [storage-files-migration-configure-sync](../../../includes/storage-files-migration-configure-sync.md)] :::row::: :::column::: [](media/storage-files-migration-server-hybrid-databox/enable-authoritative-upload-top-checkbox-expanded.png#lightbox) :::column-end::: :::column::: Once you are in the **Create server endpoint** wizard, utilize the provided checkbox underneath the folder path. Only make this selection if you have entered a path that points to the same file and folder structure as can be found in the Azure file share (where Data Box moved the files and folders into for this namespace). </br> </br> If there is a mismatch of folder hierarchy, then that will present itself as differences that cannot be automatically resolved. Avoid a mismatch or any investment in the Data Box process will result in zero benefit to you. All data will be deleted in the Azure file share. All data will need to be uploaded from the local server. The directory structures must match to gain the benefit of a bulk-migration with Azure Data Box and a seamless update of the cloud share with the latest changes from the server. :::column-end::: :::row-end::: > [!NOTE] > Enabling this checkbox will set the **Initial sync** mode to *Authoritatively overwrite files and folders in the Azure file share with content in this server's path.* This option is only available for the first server endpoint in a sync group. Once you configured authoritative upload for this new server endpoint, you can optionally enable cloud tiering. Cloud tiering is the Azure File Sync feature that allows the local server to have less storage capacity than is stored in the cloud but have the full namespace available. Locally interesting data is also cached locally for fast access performance. Cloud tiering is optional. You can set it individually for each Azure File Sync server endpoint. Use this feature to achieve a fixed storage footprint on-premises, yet still give users a local performance cache, and store cooler data in the cloud. For more information, see the [cloud tiering overview](../file-sync/file-sync-cloud-tiering-overview.md) or take a closer look at the different [cloud tiering policies](../file-sync/file-sync-cloud-tiering-policy.md) you can use to fine-tune what is cached and tiered on the local server. ## Complete your migration After you create a server endpoint, sync works. But sync needs to enumerate (discover) the files and folders you moved by using Azure Data Box into the Azure file share. Depending on the size of the namespace, it can take a long time before the latest server changes sync to the cloud. Your users aren't affected and can continue to work with the data on the server. This strategy achieves a zero-downtime cloud migration. For all Azure file shares / server locations that you need to configure for sync, repeat the steps to create sync groups and to add the matching server folders as server endpoints. You used Azure Data Box to move your files into several Azure file shares. Your migration is complete once you have created all the server endpoints that connect your on-premises data to these Azure file shares. ## Next steps There's more to discover about Azure file shares and Azure File Sync. The following articles help you understand advanced options, best practices, and troubleshooting. These articles contain links to the [Azure file share documentation](storage-files-introduction.md) where appropriate. * [Migration overview](storage-files-migration-overview.md) * [Plan for an Azure File Sync deployment](../file-sync/file-sync-planning.md) * [Create a classic file share](create-classic-file-share.md) * [Troubleshoot Azure File Sync](/troubleshoot/azure/azure-storage/file-sync-troubleshoot?toc=/azure/storage/file-sync/toc.json)