Retention aware block mapping in flash-based solid state drives

A storage device with improved retention efficiency, the storage device comprising:

• a controller configured to:
• obtain expected storage retention times for a plurality of storage blocks located within a plurality of dies by:
• estimating a bit error rate (BER) of a memory page of a first storage block of the plurality of storage blocks, and
• obtaining an expected storage retention time of the first storage block by at least extrapolating a relationship between the BER and the expected storage retention time of the first storage block, wherein the expected storage retention time of the first storage block indicates a time duration (i) during which the first storage block is expected to remain usable to retain data and (ii) after which the first storage block is expected to become unusable to retain the data;
• and
• group the plurality of storage blocks into two or more superblocks based on the expected storage retention times, wherein a respective superblock:
• is associated with a superblock retention time range;
• and
• comprises storage blocks having expected storage retention times within the superblock retention time range;
• obtain data to write to the storage device and an expected update time for a next update of a file associated with the data;
• select a first superblock based on matching the expected update time with a first superblock retention time range associated with the first superblock;
• and
• write the data to the first superblock.

A method for improving retention efficiency of a storage medium comprising a plurality of storage blocks located within a plurality of dies, the method performed by a controller and comprising:

• obtaining expected storage retention times for the plurality of storage blocks by at least:
• estimating a bit error rate (BER) of a memory page of a first storage block of the plurality of storage blocks, and
• obtaining an expected storage retention time of the first storage block by at least extrapolating a relationship between the BER and the expected storage retention time of the first storage block, wherein the expected storage retention time of the first storage block indicates a time duration (i) during which the first storage block is expected to remain usable to retain data and (ii) after which the first storage block is expected to become unusable to retain the data;
• grouping the plurality of storage blocks into two or more superblocks based on the expected storage retention times, wherein a respective superblock:
• is associated with a superblock retention time range;
• and
• comprises storage blocks having expected storage retention times within the superblock retention time range;
• obtaining data to write to the storage medium and an expected update time for a next update of a file associated with the data;
• selecting a first superblock based on matching the expected update time with a first superblock retention time range associated with the first superblock;
• and
• writing the data to the first superblock.