System and method for data recovery in a solid state storage device using optimal reference voltage values of a related storage element
View Patent ↗Embodiments of solid-state storage system are provided herein include data recovery mechanism to recover data upon detection of a read error (e.g., an uncorrectable ECC error) in a storage element such as a page. In various embodiments, the system is configured to determine optimal reference voltage value(s) by evaluating the reference voltage value(s) of page(s) that are related to the page where the failure occurred. The related page(a) may include a page that is paired with the initial page where the failure occurred (e.g., the paired pages reside in a common memory cell), or a neighboring page that is physically near the page where the initial page, and/or a paired page of the neighboring page. In another embodiment, the system is configured to perform a time-limited search function to attempt to determine optimal reference voltage values through an iterative process that adjusts voltage values in a progression to determine a set of values that can retrieve the data.
1. In a data storage device comprising a non-volatile memory array, a method for selecting reference voltage values for performing memory read operations, the method comprising:
in response to a failed attempt to read data from a first storage element of the non-volatile memory array:
determining a set of one or more reference voltage values for reading data from the first storage element based at least in part on one or more reference voltage values associated with at least one other storage element in the non-volatile memory array; and
attempting to read the data from the first storage element using the determined set of one or more reference voltage values.
2. The method of claim 1 , wherein the at least one other storage element is related to the first storage element.
3. The method of claim 2 , wherein the at least one related storage element comprises a storage element in a common memory cell as the first storage element, and wherein the determined set of one or more reference voltage values comprises one or more reference voltage values used to successfully retrieve data from the at least one related storage element.
4. The method of claim 2 , wherein the at least one related storage element comprises a storage element in a memory cell adjacent to a memory cell of the first storage element, and wherein the determined set of one or more reference voltage values comprises one or more reference voltage values used to successfully retrieve data from the at least one related storage element.
5. The method of claim 2 , wherein the at least one related storage element comprises:
(1) a second storage element in a memory cell adjacent to a memory cell of the first storage element; and
(2) a third storage element in a common memory cell as the second storage element,
wherein the determined set of one or more reference voltage values is based on a combination of:
one or more reference voltage values used to successfully retrieve data from the second storage element; and
one or more reference voltage values used to successfully retrieve data from the third storage element.
6. The method of claim 1 , further comprising:
in response to determining that the attempt to read the data from the first storage element using the determined set of one or more reference voltage values failed:
determining a revised set of one or more reference voltage values based on one or more reference voltage values of at least one another storage element; and
attempting to retrieve data from the first storage element using the revised set of one or more reference voltage values.
7. The method of claim 6 , wherein the at least one other storage element comprises a storage element in a common memory cell as the first storage element and the at least one another related storage element comprises a storage element in a memory cell adjacent to a memory cell of the first storage element.
8. The method of claim 1 , further comprising:
in response to determining that the attempt to read the data from the first storage element using the determined set of one or more reference voltage values failed:
adjusting one or more reference voltage values; and
attempting an additional read operation with the one or more adjusted reference voltage values;
in response to determining that the additional read operation successfully retrieves data from the first storage element, returning the retrieved data; and
in response to determining that the additional read operation does not successfully retrieve data from the first storage element:
determining whether a time limit has been reached;
in response to determining that the time limit has not been reached, repeating adjusting the one or more reference voltage values and attempting the additional read operation with the one or more adjusted reference voltage values; and
in response to determining that the time limit has been reached, returning a failure status.
9. The method of claim 8 , wherein each successive repetition of the adjusting adjusts the one or more reference voltage values in accordance with a succession of adjustment.
10. The method of claim 1 , further comprising:
in response to determining that the attempt to read the data from the first storage element using the determined set of one or more reference voltage values failed:
looking up in a table one or more adjusted reference voltage values; and
attempting an additional read operation with the one or more adjusted reference voltage values.
11. The method of claim 1 , wherein determining the set of one or more reference voltage values comprises:
reading the at least one other storage element with an initial set of one or more reference voltage values with an error correction mechanism that returns an indication reflecting an amount of error encountered in the read operation on a second storage element; and
adjusting at least one value within the initial set of one or more reference voltage values based at least in part on the returned indication.
12. The method of claim 11 , further comprising determining the set of one or more reference voltage values with a returned indication reflecting a minimal amount of error by repeating reading the at least one other storage element and adjusting the at least one value.
13. The method of claim 11 , wherein the error correction mechanism is error correction code (ECC) and adjusting the at least one value is based on a number of bits with error encountered in reading the at least one other storage element.
14. The method of claim 1 , wherein the failure is due to an uncorrectable ECC error.
15. The method of claim 1 , wherein each of the first and the at least one other storage elements is a page.
16. A data storage device comprising:
a non-volatile memory array comprising solid state memory devices capable of being read using reference voltage values; and
a controller configured to read data from the non-volatile memory array, the controller further configured to respond to a failure in an attempt to read data from a first storage element of the non-volatile memory array by at least:
determining a set of one or more reference voltage values for reading data from the first storage element based at least in part on one or more reference voltage values associated with at least one other storage element in the non-volatile memory array; and
attempting to read the data from the first storage element using the determined set of one or more reference voltage values.
17. The device of claim 16 , wherein the at least one other storage element is related to the first storage element.
18. The device of claim 17 , wherein the at least one related storage element comprises a storage element in a common memory cell as the first storage element, and wherein the determined set of one or more reference voltage values comprises one or more reference voltage values used to successfully retrieve data from the at least one related storage element.
19. The device of claim 17 , wherein the at least one related storage element comprises a storage element in a memory cell adjacent to a memory cell of the first storage element, and wherein the determined set of one or more reference voltage values comprises one or more reference voltage values used to successfully retrieve data from the at least one related storage element.
20. The device of claim 17 , wherein the at least one related storage element comprises:
(1) a second storage element in a memory cell adjacent to a memory cell of the first storage element; and
(2) a third storage element in a common memory cell as the second storage element,
wherein the determined set of one or more reference voltage values is based on a combination of:
one or more reference voltage values used to successfully retrieve data from the second storage element; and
one or more reference voltage values used to successfully retrieve data from the third storage element.
21. The device of claim 16 , wherein the controller is further configured to:
in response to determining that the attempt to read the data from the first storage element using the determined set of one or more reference voltage values failed:
determine a revised set of one or more reference voltage values based on one or more reference voltage values of at least one another storage element; and
attempt to retrieve data from the first storage element using the revised set of one or more reference voltage values.
22. The device of claim 21 , wherein the at least one related storage element comprises a storage element in a common memory cell as the first storage element and the at least one other related storage element comprises a storage element in a memory cell adjacent to a memory cell of the first storage element.
23. The device of claim 16 , wherein the controller is further configured to in response to determining that the attempt to read the data from the first storage element using the determined set of one or more reference voltage values failed:
adjust one or more reference voltage values;
attempt an additional read operation with the adjusted one or more reference voltage values;
in response to determining that the additional read operation successfully retrieves data from the first storage element, return the retrieved data; and
in response to determining that the additional read operation does not successfully retrieve data from the first storage element:
determine whether a time limit has been reached;
in response to determining that the time limit has not been reached, repeat adjusting the one or more reference voltage values and attempting the additional read operation with the adjusted one or more reference voltage values; and
in response to determining that the time limit has been reached, return a failure status.
24. The device of claim 23 , wherein the controller is further configured to perform each successive repetition of adjusting by adjusting the one or more reference voltage values in accordance with a succession of adjustment.
25. The device of claim 16 , wherein the controller is further configured to in response to determining that the attempt to read the data from the first storage element using the determined set of one or more reference voltage values failed:
look up in a table one or more adjusted reference voltage values; and
attempt an additional read operation with the one or more adjusted reference voltage values.
26. The device of claim 16 , wherein the controller is configured to determine the set of one or more reference voltage values by at least:
reading the at least one other storage element with an initial set of one or more reference voltage values with an error correction mechanism that returns an indication reflecting an amount of error encountered in the read operation on a second storage element; and
adjusting at least one value within the initial set of one or more reference voltage values based at least in part on the returned indication.
27. The device of claim 26 , wherein the controller is further configured to determine the set of one or more reference voltage values with a returned indication reflecting a minimal amount of error by repeating reading the at least one related storage element and adjusting the at least one value.
28. The device of claim 26 , wherein the error correction mechanism is error correction code (ECC) and adjusting the at least one value is based on a number of bits with error encountered in reading the at least one other storage element.
29. The device of claim 16 , wherein the failure is due to an uncorrectable ECC error.
30. The device of claim 16 , wherein each of the first and the at least one other storage elements is a page.
31. The device of claim 16 , wherein the solid state memory devices comprise multi-level cell (MLC) devices.
32. A data storage device comprising:
a non-volatile memory array comprising a plurality of storage elements; and
a controller configured to read data from the non-volatile memory array, the controller further configured to respond to a failure in an attempt to read data from a first storage element of the non-volatile memory array using a set of one or more reference voltage values by at least:
adjusting the one or more reference voltage values in the set;
performing an additional read operation with the adjusted one or more reference voltage values;
in response to determining that the additional read operation successfully retrieves data from the first storage element, returning the retrieved data; and
in response to determining that the additional read operation does not successfully retrieve data from the first storage element:
determining whether a time limit has been reached;
in response to determining that the time limit has not been reached, repeating adjusting the one or more reference voltage values and performing the additional read operation; and
in response to determining that the time limit has been reached, returning a failure status.
33. The device of claim 32 , wherein the controller is configured to adjust the one or more reference voltage values based at least in part on a number of ECC error bits encountered during performing a prior unsuccessful read operation.