Storage device with increased endurance
A black box device for a vehicle includes a data storage system for recording event data fed to the black box from various vehicle sensors. The data storage system includes a memory having memory cells and a controller in communication with the memory. The controller is configured to receive data and determine one or more memory cells as a destination for the data to be written. The controller is configured to determine a wear level of the memory cells and select a subset of program states of the memory cells based on the wear level; and program the memory cells using respective subsets of program states for each respective memory cell.
1. A data storage system, comprising:
a non-volatile memory (NVM) including a plurality of memory cells, wherein the NVM has a ratio of defined export capacity to physical capacity that is greater than 0.02 and less than 0.50; and
a controller coupled with the NVM, wherein the controller receives data from a host and writes the data in the NVM, wherein the controller is configured to:
calculate an error correcting code (ECC) for the received data and save the ECC with the received data, wherein an ECC code rate is less than 0.60;
determine a first memory cell of the plurality of memory cells as a destination for the data to be written, wherein the first memory cell is configured to be programmed using at least three program states;
determine a wear level of the first memory cell;
select a subset of the at least three program states, including a first program state and a second program state, for the first memory cell based on the wear level of the first memory cell to render at least one program state not included in the subset as unavailable for programming; and
program the memory cell using one of the first and second program states.
2. The data storage system of claim 1 , wherein the NVM comprises a plurality of blocks and an allowed number of grown physical bad blocks is greater than 5% and less than 95% of the plurality of blocks.
3. The data storage system of claim 1 , wherein the system is a black box recording device in a vehicle and the data from the host comprises event data generated by a plurality of vehicle sensors.
4. The data storage system of claim 1 , wherein selecting the first program state and the second program state comprises:
determining which of the at least three program states are available for programming; and
selecting, as the first program state and the second program state, two available states associated with the lowest program voltage.
5. The data storage system of claim 4 , wherein determining which of the at least three program states are available for programming comprises:
determining a distribution width or an error rate of the at least three program states; and
classifying a particular program state of the at least three program states as available for programming based on the distribution width or the error rate of the particular program state.
6. The data storage system of claim 1 , wherein selecting the first program state and the second program state comprises:
determining the wear level of the first memory cell with respect to one or more program states based on program state distribution width of the one or more program states;
shifting one of a previously selected first program state or a previously selected second program state to a new program state based on the determined wear level of the first memory cell with respect to the one or more program states.
7. The data storage system of claim 6 , wherein shifting one of the previously selected first program state or the previously selected second program state to the new program state comprises selecting, as the new program state, a program state corresponding to a higher program voltage than a program voltage of the one of the previously selected first or second program state.
8. The data storage system of claim 1 , wherein determining a wear level of the first memory cell comprises:
counting program-erase cycles (PEC) of the first memory cell; and
determining the wear level based on whether a number of PEC of the first memory cell is above a threshold.
9. The data storage system of claim 1 , wherein determining a wear level of the first memory cell comprises:
performing a diagnostic read operation on the first memory cell; and
determining a quantity of errors or a program state distribution width based on the diagnostic read operation; and
determining the wear level based on the whether the quantity of errors or the program state distribution width is above a respective threshold.
10. A method of storing data in a black box recorder system for a vehicle, the block box recorder system comprising the data storage system of claim 1 comprising a memory including a plurality of memory cells, and a controller in communication with the memory, the method comprising:
determining a first memory cell of the plurality of memory cells as a destination for the data to be written, wherein the first memory cell is configured to be programmed using at least three program states;
determining a wear level of the first memory cell;
selecting a subset of the at least three program states, including a first program state and a second program state, for first memory cell based on the wear level of the first memory cell to render at least one program state not included in the subset as unavailable for programming; and
programming the first memory cell using one of the first and second program states.
11. The method of claim 10 , wherein selecting the first program state and the second program state comprises:
determining which of the at least three program states are available for programming; and
selecting, as the first program state and the second program state, two available states associated with the lowest program voltage.
12. The method of claim 11 , wherein determining which of the at least three program states are available for programming comprises:
determining a distribution width or an error rate of the at least three program states; and
classifying a particular program state of the at least three program states as available for programming based on the distribution width or the error rate of the particular program state.
13. The method of claim 10 , wherein selecting the first program state and the second program state comprises:
determining the wear level of the first memory cell with respect to one or more program states based on program state distribution width of the one or more program states;
shifting one of a previously selected first program state or a previously selected second program state to a new program state based on the determined wear level of the first memory cell with respect to the one or more program states.
14. A data storage system, comprising a memory comprising a plurality of memory cells; and a controller in communication with the memory, the controller configured to:
receive data to be written;
determine a first memory cell of the plurality of memory cells as a destination for the data to be written, wherein the first memory cell is configured to be programmed using at least three program states;
determine a wear level of the first memory cell;
select a subset of the at least three program states, including a first program state and a second program state, for the first memory cell based on the wear level of the first memory cell to render at least one program state not included in the subset as unavailable for programming; and
program the first memory cell using one of the first and second program states.
15. The data storage system of claim 14 , wherein selecting the first program state and the second program state comprises:
determining which of the at least three program states are available for programming; and
selecting, as the first program state and the second program state, two available states associated with the lowest program voltage.
16. The data storage system of claim 15 , wherein determining which of the at least three program states are available for programming comprises:
determining a distribution width or an error rate of the at least three program states; and
classifying a particular program state of the at least three program states as available for programming based on the distribution width or the error rate of the particular program state.
17. The data storage system of claim 14 , wherein selecting the first program state and the second program state comprises:
determining the wear level of the first memory cell with respect to one or more program states based on program state distribution width of the one or more program states;
shifting one of a previously selected first program state or a previously selected second program state to a new program state based on the determined wear level of the first memory cell with respect to the one or more program states.
18. The data storage system of claim 17 , wherein shifting one of the previously selected first program state or the previously selected second program state to the new program state comprises selecting, as the new program state, a program state corresponding to a higher program voltage than a program voltage of the one of the previously selected first or second program state.
19. A black box recorder system for a vehicle, the black box recorder system comprising:
a data storage system comprising a plurality of memory cells; and
a controller in communication with the plurality of memory cells, the controller comprising:
means for determining a first memory cell of the plurality of memory cells as a destination for the data to be written, wherein the first memory cell is configured to be programmed using at least three program states;
means for determining a wear level of the first memory cell;
means for selecting a subset of the at least three program states, including a first program state and a second program state, for the first memory cell based on the wear level of the first memory cell to render at least one program state not included in the subset as unavailable for programming; and
means for programming the first memory cell using one of the first and second program states.