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    E-MapReduce:JindoFS block storage mode

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    E-MapReduce:JindoFS block storage mode

    Last Updated:Aug 24, 2026

    JindoFS in block storage mode delivers high-performance data access by storing data as blocks in an OSS storage backend and using a local cache for acceleration. A local Jindo Namespace Service manages metadata, providing fast and efficient operations. This topic describes the JindoFS block storage mode and how to use it.

    Background information

    JindoFS block storage mode has the following features:

    • Unlimited elastic storage capacity: OSS serves as the storage backend. Storage is not limited by the local cluster, and the local cluster can be freely scaled in or out.
    • Local read acceleration: JindoFS uses the storage resources of the local cluster to accelerate data reads. This mode is suitable for clusters that have local storage capabilities, and improves read throughput even with limited local storage. It is particularly effective for Write Once Read Many (WORM) workloads.
    • High-performance metadata operations: Metadata operation efficiency is comparable to that of HDFS. This avoids the latency of OSS file system metadata operations and the instability that frequent access may cause.
    • Data locality: Data locality is maximized when jobs are running, which reduces network traffic and further improves read performance.

    Configuration

    1. Go to the SmartData service.
      1. Log on to the EMR console.
      2. In the top navigation bar, select a region and a resource group as needed.
      3. Click the Clusters tab.
      4. On the Clusters page, find your cluster and click Details in the Actions column.
      5. In the navigation pane on the left, choose Services > SmartData.
    2. Go to the bigboot service configuration page.
      1. Click the Configure tab.
      2. Click bigboot .
    3. Configure the following parameters.
      JindoFS supports multiple namespaces. This topic uses test as an example namespace.
      1. Set jfs.namespaces to test.
        test is an example namespace name. To configure multiple namespaces, separate their names with commas (,).
      2. Click Custom Configuration. In the Add Configuration Item dialog box, add the following parameters and click OK.
        Parameter Description Example
        jfs.namespaces.test.oss.uri The OSS storage backend for the test namespace. oss://<oss_bucket>/<oss_dir>/
        Note We recommend you specify a directory within an OSS bucket. JindoFS stores the data blocks for the namespace in this directory.
        jfs.namespaces.test.mode The storage mode for the test namespace. block
        jfs.namespaces.test.oss.access.key The AccessKey ID for the OSS storage backend. xxxx
        Note For optimal performance and stability, we recommend using an OSS bucket in the same account and region as your E-MapReduce cluster. In this case, the E-MapReduce cluster can access OSS without credentials, and you do not need to configure the AccessKey ID and AccessKey Secret.
        jfs.namespaces.test.oss.access.secret The AccessKey Secret for the OSS storage backend.
      3. Click OK.
    4. In the upper-right corner, click Save.
    5. In the upper-right corner, choose Actions > Restart Jindo Namespace Service.
      After the service restarts, you can access files in JindoFS using the path jfs://test/<path_of_file>.

    Disk space watermark control

    JindoFS uses OSS as its storage backend, which provides vast storage capacity. However, the local disk space on your cluster is finite. To manage this space, JindoFS automatically evicts cold data from the local cache. You can control this eviction behavior with the storage.watermark.high.ratio and storage.watermark.low.ratio parameters. These parameters accept decimal values between 0 and 1 that represent the ratio of disk space used.

    1. Configure the disk watermarks.
      In the Service Configuration section, click the storage tab and modify the following parameters.
      Parameter Description
      storage.watermark.high.ratio The high watermark for disk usage. When the disk space used by the JindoFS data directory on a data disk reaches this ratio, JindoFS triggers a cleanup process. Default value: 0.4.
      storage.watermark.low.ratio The low watermark for disk usage. After the cleanup process is triggered, JindoFS deletes cold data until the disk space used by the JindoFS data directory drops to this ratio. Default value: 0.2.
      Note You can set the high watermark to control the amount of disk space allocated to JindoFS. The low watermark must be less than the high watermark. Set reasonable values for your workload.
    2. Save the configuration.
      1. In the upper-right corner, click Save.
      2. In the Confirm dialog box, enter a reason for the change, and turn on Auto-update Configuration.
      3. Click OK.
    3. Restart the Jindo Storage Service to apply the changes.
      1. In the upper-right corner, choose Actions > Restart Jindo Storage Service.
      2. In the Cluster Activities dialog box, set the required parameters and click OK.
      3. In the Confirm dialog box, click OK.