If a requester accesses data in your bucket but the data does not exist in your bucket, 404 Not Found is returned. If you configure back-to-origin rules that contain a valid origin for the bucket, the requester can obtain the data based on the rules. You can configure mirroring-based or redirection-based back-to-origin rules for hot migration and specific request redirection.

Principles and scenarios of the mirroring-based and redirection-based back-to-origin rules:

  • After you configure mirroring-based back-to-origin rules for a bucket, if the object that a requester accesses does not exist in your bucket, OSS obtains the object from the origin specified by the back-to-origin rules. OSS returns the object obtained from the origin to the requester and stores the object in the bucket. Mirroring-based back-to-origin is used to seamlessly migrate data to OSS. For more information about mirroring-based back-to-origin, see Mirroring-based back-to-origin.
  • After you configure redirection-based back-to-origin rules for a bucket, if an error occurs when a requester accesses the bucket, OSS redirects the request to the origin specified by the redirection-based back-to-origin rules. You can use this feature to redirect requests for objects and develop various services based on redirection. For more information about redirection-based back-to-origin, see Redirection.