Object Storage Service:Use hierarchical namespace

Benefits

• Atomic operations on directories

  If a bucket uses a flat namespace in which real directories are not supported, applications may need to process millions of objects to complete a task at the directory level. In contrast, if the hierarchical namespace feature is enabled for a bucket, applications can update a parent directory in a single atomic operation to complete multiple directory-level tasks at the same time.

• Optimized performance

  Compared with a flat namespace, a hierarchical namespace eliminates the need to replicate or convert data before the data is analyzed. This improves the performance of directory management. The hierarchical namespace feature is especially important for big data analytics frameworks. For example, Hive or Spark writes output results to a temporary directory during task execution and renames the directory after the task is complete. In a flat namespace, the time that is consumed to rename the directory is usually longer than the time that is consumed to perform the task.

Procedure

1. Enable hierarchical namespace.

   You can enable the hierarchical namespace feature for a bucket only when you create the bucket. The hierarchical namespace feature cannot be disabled after it is enabled for a bucket. For more information about how to enable hierarchical namespace, see Create buckets.

2. Perform directory-level operations on a bucket for which the hierarchical namespace feature is enabled.

   The following table describes the methods that you can use to create, rename, or delete directories in a bucket for which the hierarchical namespace feature is enabled.

   Implementation method	Description
   OSS console Create a directory Rename a directory Delete a directory	A user-friendly and intuitive web application
   Java SDK	Simple and easy-to-use SDK demos

Usage notes

• Supported regions

  The hierarchical namespace feature is available only in the following regions: US (Silicon Valley), Japan (Tokyo), India (Mumbai) Closing Down, UK (London), and Malaysia (Kuala Lumpur).

• Create directories

  A directory name cannot contain consecutive forward slashes (/).

  Data cannot be written to directories. The Content-Length of a directory can be set only to 0.

  The Content-Type of a directory can be set only to application/x-directory.

• Rename a directory or object

  The name of a renamed directory or object cannot be the same as the name of an existing directory or object in the same bucket.

  The parent directory that is included in the name of a renamed directory or object must exist. For example, if you rename a directory to destfolder/examplefolder/test, the parent directory destfolder/examplefolder must exist in the bucket.

• Delete directories

  • Recursive delete

    Recursive delete is used to delete a directory and all objects and subdirectories within the directory. To use recursive delete, you must have the DeleteObject permission on the directory and all objects and subdirectories within the directory that you want to delete.

    For example, if you want to use recursive delete to delete the dest/testfolder directory and the objects in the directory, you must have the DeleteObject permission on dest/testfolder and dest/testfolder/*.

    Important

    If a concurrent request is sent to write data to a directory when you use the recursive delete method to delete the directory, the directory may fail to be deleted.

  • Non-recursive delete

    Non-recursive delete is used to delete empty directories. To use non-recursive delete, you must have the DeleteObject permission on the directory that you want to delete.

Unsupported features

The following table describes the features that are not supported by buckets for which the hierarchical namespace feature is enabled.