Patent attributes
A distributed storage system includes a primary storage system and a secondary storage system. The secondary storage system stores the actual data and the primary storage system stores metadata for the actual data. The metadata references at the primary storage system may be deleted without deleting the corresponding data at the secondary storage system. Snapshots of the metadata at the primary storage system are sent to the secondary storage system. The secondary storage system can compare two metadata snapshots received from the primary storage in order to determine whether data stored at the secondary storage system has been deleted at the primary storage system for longer than a retention period. Such data may be deleted to free up storage space at the secondary storage server.
