Data mapping enabling fast read multi-level 3D NAND to improve lifetime capacity
In this disclosure, data mapping based on three dimensional lattices that have an improved sum rate (i.e., lifetime capacity) with low read latency is disclosed. During the write, a memory location is written to multiple times prior to erasure. Specifically, for the first write, there are 4/3 bits per cell available for writing, which is about 10.67 kB per cell are used for data storage. Then, for the second write, there is one bit per cell, which is 8 kB per cell for data storage. If considering a block with 128 different cells and writing 32 kB of data, the first write results in 42.66 data writes while the second write results in 32 writes for a total of 74.66 writes. Previously, the number of writes for 32 kB would be 64 writes. Thus, by writing twice prior to erasure, more data can be stored.
1. A method, comprising:
writing a first set of data to a NAND flash block in a first memory location, wherein writing the first set of data utilizes less than all of the first memory location, wherein 4/3 bits per cell are available for writing the first set of data;
writing a second set of data to the first memory location, wherein writing the second set of data utilizes the remainder of the first memory location, wherein 1 bit per cell is available for writing the second set of data; and
erasing the first memory location, wherein writing the second set of data occurs prior to erasing the first set of data and wherein the method occurs within a solid state drive and the writing of the first set of data and the second set of data use two write rewrite codes and wherein the codes use a current Gray mapping between logical data and physical cell levels.
2. The method of claim 1 , wherein the NAND flash block is TLC.
3. The method of claim 1 , wherein the NAND flash block is MLC.
4. The method of claim 3 , wherein the first memory location is a 16 kB storage location and wherein writing the first set of data comprises writing data to about 10 kB of the first memory location.
5. The method of claim 4 , wherein writing the second set of data comprises writing data to about 8 kB of the first memory location.
6. The method of claim 5 , wherein the about 10 kB is different from the about 8 kB.
7. The method of claim 5 , wherein the first set of data is present in the first memory location when the second set of data is written to the first memory location.
8. The method of claim 5 , wherein the first set of data is present in the first memory location after the second set of data is written to the first memory location.
9. The method of claim 1 , wherein the memory location is disposed within a memory block at the intersection of a word line and a bit line.
10. A system, comprising:
a processor; and
a memory system storing instructions that, when executed by the processor, cause the system to:
write a first set of data to a NAND flash block in a first memory location, wherein writing the first set of data utilizes less than all of the first memory location, wherein 4/3 bits per cell are available for writing the first set of data;
write a second set of data to the first memory location, wherein writing the second set of data utilizes the remainder of the first memory location, wherein 1 bit per cell is available for writing the second set of data; and
erase the first memory location, wherein writing the second set of data occurs prior to erasing the first set of data and wherein the system is a solid state drive and the writing of the first set of data and the second set of data use two write rewrite codes and wherein the codes use a current Gray mapping between logical data and physical cell levels.
11. The system of claim 10 , wherein the NAND flash block is TLC.
12. The system of claim 10 , wherein the NAND flash block is MLC.
13. The system of claim 10 , wherein the first memory location is a 32 kB storage location and wherein writing the first set of data comprises writing data to about 10 kB of the first memory location.
14. The system of claim 13 , wherein writing the second set of data comprises writing data to about 8 kB of the first memory location.
15. The system of claim 14 , wherein the about 10 kB is different from the about 8 kB.
16. The system of claim 14 , wherein the first set of data is present in the first memory location when the second set of data is written to the first memory location.
17. The system of claim 14 , wherein the first set of data is present in the first memory location after the second set of data is written to the first memory location.
18. The system of claim 10 , wherein the memory location is disposed within a memory block at the intersection of a word line and a bit line.
19. A non-transitory computer readable storage medium, containing instructions that, when executed by a processor, cause a computer system to burn files after a read process has been completed, by performing the steps of:
write a first set of data to a NAND flash block in a first memory location, wherein writing the first set of data utilizes less than all of the first memory location, wherein 4/3 bits per cell are available for writing the first set of data;
write a second set of data to the first memory location, wherein writing the second set of data utilizes the remainder of the first memory location, wherein 1 bit per cell is available for writing the second set of data; and
erase the first memory location, wherein writing the second set of data occurs prior to erasing the first set of data, wherein the first memory location is within a solid state drive and the writing of the first set of data and the second set of data use two write rewrite codes and wherein the codes use a current Gray mapping between logical data and physical cell levels.
20. The storage medium of claim 19 , wherein the NAND flash block is TLC.
21. The storage medium of claim 19 , wherein the NAND flash block is MLC.
22. The storage medium of claim 19 , wherein the first memory location is a 32 kB storage location and wherein writing the first set of data comprises writing data to about 10 kB of the first memory location.
23. The storage medium of claim 22 , wherein writing the second set of data comprises writing data to about 8 kB of the first memory location.
24. The storage medium of claim 23 , wherein the about 10 kB is different from the about 8 kB.
25. The storage medium of claim 24 , wherein the first set of data is present in the first memory location when the second set of data is written to the first memory location.
26. The storage medium of claim 24 , wherein the first set of data is present in the first memory location after the second set of data is written to the first memory location.
27. The storage medium of claim 19 , wherein the memory location is disposed within a memory block at the intersection of a word line and a bit line.