Memory block allocation by block health

A method, comprising:

• calculating a block health metric (BHM) value for each of a plurality of blocks of non-volatile memory storage elements, the BHM values quantifying a health of each block as a function of a Program-Erase Count (PEC) of the block and a Bit Error Rate (BER) of the block;
• ranking the plurality of blocks in order of the BHM values calculated for each of the blocks from a healthiest block to a least-healthiest block, the healthiest block having a higher PEC count than one or more lower-ranked blocks in the ranking;
• and
• selecting a block for use in a write operation based on the ranking, comprising selecting a highest-ranked block in a pool of free blocks, the highest-ranked block having a higher PEC than a PEC of one or more other blocks in the pool.

A non-volatile memory system, comprising:

• a plurality of blocks of non-volatile memory storage elements, wherein each block is individually erasable;
• an error rate calculation circuit configured to calculate an error rate for each block;
• a program-erase cycle count circuit configured to count program-erase cycles experienced by each block;
• a block health metric calculator configured to calculate a multi-factor health metric for each of the blocks, the multi-factor health metric for each block comprising a combination of a plurality of block health factors, comprising the error rate of the block, as calculated by the error rate calculation circuit, and the program-erase cycle count of the block obtained from the program-erase cycle count circuit;
• and
• control circuitry configured to:
• generate an entry for each block, the entry for each block comprising the error rate of the block, the program-erase cycle count of the block, and the multi-factor health metric calculated for the block, the entries configured to distinguish free blocks that are available for use in write operations from programmed blocks;
• determine a health ordering of the entries according to the multi-factor health metrics calculated for the corresponding blocks, such that a position of each entry in the determined health ordering indicates a relative health of the corresponding block compared to the plurality of blocks;
• and
• select a block for use in a write operation from blocks identified as being free blocks by the entries, the control circuitry configured to select the block according to a position of an entry corresponding to the selected block in the determined health ordering, wherein a multi-factor health metric calculated for the selected block indicates that the selected block is a healthiest block of the free blocks, the selected block having a higher program-erase cycle count than one or more of the free blocks not selected for use in the write operation.