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    Cloud Storage Gateway:Configure express synchronization

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    Cloud Storage Gateway:Configure express synchronization

    Last Updated:May 07, 2026

    The express synchronization feature of a file gateway in Cloud Storage Gateway (CSG) allows you to efficiently synchronize changes in an Object Storage Service (OSS) bucket to all local clients that are connected to the bucket.

    Prerequisites

    • A file gateway is created, and a cache disk is attached to it. For more information, see Manage file gateways and Add a cache.

    • An OSS bucket is created. For more information, see Get started by using the OSS console.

      Important

      • File gateways support the following storage classes of OSS buckets: Standard, Infrequent Access (IA), and Archive. File gateways do not support OSS buckets for which back-to-origin routing is configured.

      • We recommend that you do not associate a gateway with an Archive bucket. If files that are written from a file gateway to OSS are infrequently modified, we recommend that you store the files in a Standard or IA bucket first and configure a lifecycle rule that changes the storage class of the files to Archive or Cold Archive. This reduces unnecessary restoration operations and optimizes storage costs and efficiency.

      • When a client writes a file to a file gateway, the gateway records at least two actions: writing the file and setting the file modification time. The gateway merges the two actions where possible. However, the gateway may still initiate multiple operations on the object to the bucket where the object is stored. The CopyObject operation is called to store the file modification time as a piece of metadata of the object in the bucket. If the object is an Archive or Cold Archive object, this operation requires object restoration, which takes some time to complete. This increases the time required for object uploads and even causes upload failures if not enough time is left to upload data in the cache.

    • A Network File System (NFS) or Server Message Block (SMB) share is created and configured for the file gateway. For more information, see Manage shares.

    • Simple Message Queue (SMQ) is activated. For more information, see Activate SMQ and authorize RAM users to access SMQ.

    Background information

    When you configure the express synchronization feature, you can add one or more shares that are connected to the same OSS bucket to an express synchronization group. All data changes in the bucket are synchronized to local clients that are associated with shares in the express synchronization group. You do not need to separately synchronize data changes from the bucket. This improves the efficiency and accuracy of synchronization.

    The Express Sync feature relies on Simple Message Queue (formerly MNS) and therefore incurs usage fees. For more information, see Billing.

    Create a synchronization group

    Important

    If you delete an object from a versioning-enabled bucket without specifying a version ID, the DeleteObject and DeleteObjects event notifications are not triggered. This is because a request to delete an object from a versioning-enabled bucket without a version ID specified does not actually delete any object version. Instead, the current version of the object is made a previous version and a delete marker is added as the current version of the object. As a result, CSG detects no deletion operation on the object.

    To enable express synchronization, you must create a synchronization group and add shares to the group. To create a synchronization group, perform the following steps:

    1. Navigate to the Express Sync page in the CSG console. On the Sync Groups page, click Create.

    2. On the Basic Information tab of the Create Sync Group page, configure the following parameters, and then click Next.

      Parameter

      Description

      Sync Group Name

      Enter the name of the synchronization group.

      Note

      The name must be 1 to 128 characters in length, and can contain letters, digits, periods (.), underscores (_), and hyphens (-). It must start with a letter.

      OSS Region

      Specify the region where the OSS bucket resides.

      Bucket Name

      Select the name of the OSS bucket. You can select only one OSS bucket for an express synchronization group. All data changes in the bucket are synchronized to the local clients that are associated with shares in the group.

      Note

      If no share is connected to the OSS bucket, no OSS bucket is available in the drop-down list. In this case, you must create a share that connects to the OSS bucket. For more information, see Manage shares.

      Bucket Subdirectory

      Select a specific subdirectory of the bucket from which you want to synchronize data.

    3. On the Create Sync Group page, in the Sync Group Settings section, select the shares that you want to add to the synchronization group from the Available Shares area on the left, and click the > icon. The selected shares are added to the Selected Shares area. Then, click Next.

      You can also select a share from the Selected Shares list and click the < icon to remove it from the synchronization group.

      Note

      After you add an NFS share to a synchronization group, you can specify the noac parameter when you mount the share to a local directory. This allows you to view the synchronization result at the earliest opportunity. For more information, see Access an NFS share.

    Manage a synchronization group

    After you create a synchronization group, all data changes in the OSS bucket are automatically synchronized to local clients that are associated with the shares in the synchronization group. You can perform the following operations to manage a synchronization group:

    • View the details of the synchronization group

      1. On the Sync Groups page, click the name of a synchronization group in the Sync Group Name column, or click Details in the Actions column for the group.

      2. In the Sync Group Details dialog box, you can view the details of a synchronization group. You can also view the details in a list format by selecting the icon or in a map format by selecting the icon in the upper-right corner. In addition to the basic information about the synchronization group and the shares added to it, the list page of the Sync Group Details dialog box also contains the following information.

        Parameter

        Description

        Message Topic Name

        The name of the SMQ topic for the synchronization group.

        Shared Status

        The status of the share in the synchronization group. The share can be in one of the following states:

        • Full Data Sync Awaiting: The share has just been added to the group and is waiting for the initial full data sync.

        • Full Data Sync in Progress: The initial full data sync for the share is in progress.

        • Sync Normal: The share is synchronizing normally.

        • Express Sync Disabled: The Express Sync feature is not enabled for the share.

        • Message Queue Inaccessible: The message queue corresponding to the share is inaccessible.

        • Message Topic Inaccessible: The message topic corresponding to the share is inaccessible.

        • Message Queue and Topic Inaccessible: Both the message queue and topic corresponding to the share are inaccessible.

        Message Queue Name

        The name of the queue that is used by the synchronization group.

    • Add a share to or remove a share from a synchronization group

      In the Actions column for the synchronization group, click Settings. In the Set Sync Group dialog box, add or remove shares. The method is the same as in Step 3 of creating a synchronization group.

    • Delete a synchronization group

      To delete a synchronization group, click Delete in the Actions column for the group. Then, in the confirmation dialog box, click OK.