US Patent 10489289 Physical media aware spacially coupled journaling and trim

An indirection mapping data structure can maintain a mapping between logical block addresses used by a host computer and physical data storage locations on an SSD. The indirection mapping data structure can include a existence map as well as a user data map. Trim data may be received from a host computer or other entity and may be used to mark particular logical addresses that are not in use as trimmed. To ensure trim data persists even if the indirection mapping data structure is lost, the existence map may be regularly stored to disk. The existence map can be journaled in the same way as user data stored to disk. When the indirection mapping data structure is rebuilt, the spatially coupled journals can be retrieved from the predefined scattered locations and used to identify the stored trim data which can be used to rebuild the existence map.