Versioning

Scenarios

OBS can store multiple versions of an object. You can quickly search for and restore different versions or restore data in the event of accidental deletions or application faults.

By default, versioning is disabled for a new OBS bucket. New objects will overwrite existing objects in the bucket in case they have the same names.

Constraints

When you enable WORM for a bucket, OBS automatically enables versioning and versioning cannot be suspended later for that bucket.

Enabling Versioning

• Enabling versioning does not change the version ID (null) and content of any existing object in a bucket. After versioning is enabled for a bucket, if you upload a new object with the same name as an existing object, a version ID will be assigned to this new object, as shown in Figure 1.
  Figure 1 Versioning (with existing objects)
  
• In a versioning-enabled bucket, OBS automatically assigns a unique version ID to each newly uploaded object. Objects with the same name are stored in OBS with different version IDs, as shown in Figure 2.
  Figure 2 Versioning (for new objects)
  

  Table 1 Version description

  Version	Description
  Latest version	After versioning is enabled, each operation on an object will result in saving of the object with a new version ID. The version ID generated upon the latest operation is called the latest version.
  Historical version	After versioning is enabled, each operation on an object will result in saving of the object with a new version ID. Version IDs generated upon operations other than the latest operation are called historical versions.

• The latest objects in a bucket are returned by default after a GET Object request.
• Objects can be downloaded by version IDs. By default, the latest object is downloaded if the version ID is not specified. For details, see Related Operations in Versioning.
• You can select an object and click Delete on the right to delete the object. After the object is deleted, OBS inserts a delete marker with a unique version ID for that object, and the deleted object is displayed in the Deleted Objects list. For details, see Deleting an Object. If attempts are then made to access this deleted object, error 404 will be returned.
  Figure 3 Object with a delete marker
  
• You can recover a deleted object by deleting the delete marker. For details, see Related Operations.
• After an object is deleted, you can specify the version number in Deleted Objects to permanently delete the object of the specified version. For details, see Deleting Objects from a Bucket with Versioning Disabled, Suspended, or Enabled.
• An object appears in either the object list or the list of deleted objects. It will never appear in both lists at the same time.

  For example, after object A is deleted, it will appear in the Deleted Objects list. If you later upload another object with the same name A, the new object A will appear in the Objects list, but the previously deleted object A will disappear from the Deleted Objects list. For details, see Figure 4.

  Figure 4 Uploading a namesake object after the original one is deleted
  
• All object versions except those with Delete Marker stored in OBS are charged.

Suspending Versioning

Once versioning is enabled for a bucket, it cannot be disabled, but it can be suspended. When versioning is suspended, a null, not a specific version ID, will be allocated to a newly uploaded object. If the newly uploaded object has the same name as an existing object with a null version ID, the new object will overwrite the existing object.

Figure 5 Object versions in the scenario when versioning is suspended

If versioning is no longer needed, you can suspend it. After versioning is suspended:

• Existing object versions are still retained in OBS. If you no longer desire these versions, manually delete them.
• Objects can be downloaded by version IDs. By default, the latest object is downloaded if the version ID is not specified.
• All historical object versions except those with Delete Marker stored in OBS are charged.

Differences Between Scenarios When Versioning Is Suspended and Disabled

If you delete an object from a versioning-suspended bucket, a delete marker with a null version ID will be generated, no matter whether the object has historical versions. But, if versioning is disabled, the same operation will not generate a delete marker.

In a versioning-enabled bucket, each historical version of an object is stored and you will be billed for the storage of all object versions. Therefore, enable versioning when necessary.

Ways to Configure Versioning

You can use OBS Console, APIs, or SDKs to configure versioning.

Related Operations

After versioning is configured for a bucket, you can go to the object details page, click the Versions tab, and then delete, share, and download object versions, and extend the retention period of an object version.

1. In the navigation pane of OBS Console, choose Object Storage.
2. In the bucket list, click the bucket you want to operate. The Objects page is displayed.
3. In the object list, click the object you want to go to the object details page.
4. On the Versions tab page, view all versions of the object.
5. Perform the following operations on object versions:
   1. Download a desired version of the object by clicking Download in the Operation column.
      

      If the version you want to download is in the Archive or Deep Archive storage class, restore it first.

   2. Share a version of the object by clicking Share in the Operation column.
   3. Delete a version of the object by choosing More > Delete in the Operation column. If you delete the latest version, the most recent version will become the latest version.
      

      In a WORM-enabled bucket, if an object has no retention policy configured or its retention policy has expired, you can delete a desired object version on the object's Versions tab page. If an object version is within the retention period, it cannot be deleted.

   4. Locate the object version for which you want to extend the retention period, choose More > Extend Retention Period, and select a date. A retention period can only be extended, but not shortened.