Enabling faster and regulated device initialization times
A method and memory apparatus that operate to minimize and limit memory initialization time when powering up after an unexpected shutdown. Instead of relying only on a cached log table that is lost when memory powers down unexpectedly, the method and apparatus disclosed herein preserve the information needed to rebuild the log table within predefined memory locations. These predefined locations are optimized such that parallel sensing will capture initialization information for a certain number of word lines across all dies and planes within the memory structure during a single read operation at power up.
1. A method, comprising:
writing data blocks to word lines across a first plane and a second plane of a memory array;
generating a first index that relates a logical block address and a physical address for certain data blocks written to the memory array;
storing the first index to a subsequent word line of the first plane, in response to a number of the data blocks written to the memory array satisfying a flush threshold;
generating a second index that relates a logical block address and a physical address for certain data blocks written to the memory array; and
storing the second index to a subsequent word line of the second plane, in response to the number of the data blocks written to the memory array satisfying the flush threshold.
2. The method of claim 1 , further comprising recovering an address mapping table for the memory array by reading the first index and second index concurrently such that an initialization operation satisfies a timing metric.
3. The method of claim 1 , further comprising storing an address mapping table periodically on the memory array.
4. The method of claim 1 , wherein the index comprises a relationship between the logical block addresses and the physical addresses for the data blocks written after storage of an address mapping table on the memory array.
5. The method of claim 1 , wherein the memory array comprises an array of memory die, each memory die comprising a physical erase block comprising the word lines, the array of memory die comprising a logical erase block comprising a physical erase block from each of the memory dies, wherein the flush threshold comprises a number of data blocks that fill a logical word line of the logical erase block and the subsequent word line comprises a logical word line adjacent to a last programmed logical word line.
6. The method of claim 1 , further comprising:
in response to determining that a last shutdown event was an ungraceful shutdown event, executing an initialization operation, the initialization operation comprising:
reading an address mapping table from the memory array into volatile memory;
reading one or more indexes from the memory array using a single read operation, the one or more indexes stored after the address mapping table was written to the memory array; and
updating the address mapping table in the volatile memory to associate the logical block addresses of the one or more indexes with the data blocks stored on the memory array after the address mapping table was written to the memory array.
7. The method of claim 1 , further comprising:
setting the flush threshold to a first value in response to memory cells of the memory array comprising single-level cells; and
setting the flush threshold to a second value in response to the memory cells of the memory array comprising multi-level cells.
8. The method of claim 1 , further comprising configuring the flush threshold based on a health metric for the memory array.
9. The method of claim 8 , wherein the health metric comprises a frequency a physical erase block comprising the word lines has completed a program and erase cycle.
10. The method of claim 1 , wherein storing the first index comprises writing the first index to a data block of the subsequent word line at a predefined location and wherein storing the second index comprises writing the second index to a data block of the subsequent word line at another predefined location.
11. The method of claim 10 , in response to the number of the data blocks satisfying the flush threshold:
writing a second set of data blocks to word lines across a first plane, a second plane, and a third plane of the memory die;
generating a third index that relates the logical block address for data blocks of the second set of data blocks and the physical address of data blocks of the second set of data blocks on the memory die; and
writing the third index to the subsequent word line, in response to a number of the data blocks of the second set of data blocks satisfying the flush threshold.
12. The method of claim 11 , wherein the first index, the second index, and the third index are written such that a single read operation reads the first index, the second index, and the third index.
13. The method of claim 1 , wherein the flush threshold comprises a flush distance, the flush distance comprising a number of the word lines of the data blocks to track by way of an index.