Logical to physical data storage mapping

A storage system, comprising:

• a storage device comprising a plurality of garbage collection units (GCUs);
• and
• a controller comprising a map and operable to, upon a write of new data associated with a logical mapping unit (LMU) to a first GCU,
• increment a total number of physical mapping units used to store logical mapping units with valid data in the first GCU based on a number of physical units occupied by the new data from a new map entry associated with the LMU in the map,
• decrement a total number of physical mapping units used to store logical mapping units with valid data in a second GCU, the second GCU containing old data associated with the LMU, based on a number of physical units occupied by the old data from an old map entry associated with the LMU in the map, and
• recycle the second GCU when the total number of physical mapping units used to store logical mapping units with valid data of the second GCU is below the total number of physical mapping units used to store logical mapping units with valid data of the first GCU.

A non-transitory memory storing instructions that, when executed by a processor of a controller associated with a storage device, cause the controller to:

• upon a write of new data associated with a logical mapping unit (LMU) a first garbage collection unit (GCU) of the storage device, increment a total number of logical mapping units stored in the first GCU;
• increment a number of logical mapping units with valid data stored in the first GCU;
• decrement a number of logical mapping units with valid data stored in a second GCU, the second GCU containing old data associated with the LMU;
• compute an average compression rate of data stored in the first and second GCUs based on the total number of logical mapping units stored in the GCU, a size of a logical mapping unit, a total number of physical mapping units in the GCU, and a size of a physical mapping unit;
• compute a size of valid data bytes stored in the first and second GCUs by multiplying the number of logical mapping units with valid data stored in the GCU by the size of a logical mapping unit and dividing by the average compression rate of data stored in the GCU;
• and
• decide whether to recycle the second GCU based on a comparison of the size of valid data bytes stored in the second GCU and the size of valid data bytes stored in the first GCU.