Garbage Collection with Demotion of Valid Data to a Lower Memory Tier

An apparatus comprising:

• a multi-tier memory structure comprising a plurality of non-volatile memory tiers each having different data transfer attributes and corresponding memory cell constructions, wherein an upper memory tier in the multi-tier memory structure is arranged into a plurality of garbage collection units (GCUs), each GCU comprising a plurality of non-volatile memory cells that are allocated and reset as a unit;
• a storage manager adapted to store a plurality of data sets in a selected GCU in the upper memory tier;
• and
• a garbage collection engine adapted to perform a garbage collection operation upon the selected GCU by identifying at least one of the plurality of data sets as a valid data set, demoting the valid data set to a non-volatile lower tier of the multi-tier memory structure, and invalidating a storage state of each of the plurality of non-volatile memory cells in preparation for storage of new data to the selected GCU.