Hybrid-HDD with improved data retention
Data are refreshed in a nonvolatile solid-state device to significantly reduce the likelihood of data retention errors. Test data are written in a region of the nonvolatile solid-state device when user data are stored in the nonvolatile solid-state device, and are subsequently read to detect the possibility of data retention errors occurring when the associated user data are read. The test data may be a portion of the user data or a predetermined test pattern. To increase sensitivity to incipient charge leakage that may compromise the user data, the test data may be written using a modified write process and/or read with a modified read operation. The nonvolatile solid-state device may be employed as part of a solid-state drive or as the flash-memory portion of a hybrid hard disk drive.
1. A method of refreshing data in a non-volatile solid-state device divided into a plurality of regions including a first region that has written therein first test data and first user data and a second region that has written therein second test data and second user data, the method comprising:
detecting a condition to perform testing;
in response to detecting the condition, measuring a quality of the first test data and a quality of the second test data;
determining that the quality of the first test data exceeds a threshold and the quality of the second test data is below the threshold;
in response to the quality of the first test data exceeding the threshold, maintaining the first user data in the first block;
in response to the quality of the second test data being below the threshold, rewriting the second user data in a third region of the non-volatile solid-state device; and
after rewriting the second user data in the third region, indicating that the second region is available for reuse.
2. The method of claim 1 , wherein the non-volatile solid-state device is a hybrid HDD device.
3. The method of claim 2 , wherein measuring the quality of the first test data comprises reading the first test data using a read threshold that is selected to increase a likelihood of read errors occurring.
4. The method of claim 2 , wherein measuring the quality of the first test data comprises:
reading the first test data; and
tracking a number of bit errors associated with reading the first test data.
5. The method of claim 1 , wherein
the first test data include a predetermined data test pattern that is written in the first region with a first write programming voltage, and
the first user data are written in the first region with a second write programming voltage that is greater than the first write threshold voltage.
6. The method of claim 1 , wherein
the first test data include a predetermined data test pattern that is written in the first region with a write operation that uses a first write period, and
the first user data are written in the first region with a write operation that uses a second write period that is longer than the first write period.
7. The method of claim 1 , wherein the test data includes a predetermined data test pattern or user data, or a combination of both.
8. A non-volatile solid-state device, comprising:
a plurality of data storage regions including a first region that has written therein first test data and first user data and a second region that has written therein second test data and second user data; and
a controller configured to:
detect a condition to perform testing;
in response to detecting the condition, measure a quality of the first test data and a quality of the second test data;
determine that the quality of the first test data exceeds a threshold and the quality of the second test data is below the threshold;
in response to the quality of the first test data exceeding the threshold, maintain the first user data in the first block;
in response to the quality of the second test data being below the threshold, rewrite the second user data in a third region of the non-volatile solid-state device; and
after rewriting the second user data in the third region, indicate that the second region is available for reuse.
9. The non-volatile solid-state device of claim 8 , wherein the first region comprises a first erasable block of the non-volatile solid-state device and the second region comprises a second erasable block of the non-volatile solid-state device.
10. The non-volatile solid-state device of claim 9 , wherein the first test data are written in a first page of the first erasable block.
11. The non-volatile solid-state device of claim 9 , wherein the first test data are written in the first region before the first user data are written in the first region.
12. The non-volatile solid-state device of claim 8 , wherein the first region comprises a single erasable block from each of a plurality of memory dies of the non-volatile solid-state device, and the second region comprises a single erasable block from each of the plurality of memory dies.
13. The non-volatile solid-state device of claim 8 , wherein the non-volatile solid-state device is a hybrid HDD device.
14. The non-volatile solid-state device of claim 13 , wherein the controller is configured to measure the quality of the first test data by reading the first test data using a read threshold that is selected to increase a likelihood of read errors occurring.
15. The non-volatile solid-state device of claim 13 , wherein the condition for initiating testing comprises one of powering on of the non-volatile solid-state device, expiration of a predetermined time interval, detection of a number of program/erase cycles that exceeds a predetermined value, and detection of a number of read errors associated with data stored in the first region or the second region that exceeds a predetermined maximum value.
16. The non-volatile solid-state device of claim 13 , wherein the controller is configured to measure the quality of the first test data by:
reading the first test data; and
tracking a number of bit errors associated with reading the first test data.
17. The non-volatile solid-state device of claim 8 , wherein
the first test data include a predetermined data test pattern that is written in the first region with a first write threshold voltage, and
the first user data are written in the first region with a second write threshold voltage that is greater than the first write threshold voltage.
18. The non-volatile solid-state device of claim 8 , wherein
the first test data include a predetermined data test pattern that is written in the first region with a write operation that uses a first write period, and
the first user data are written in the first region with a write operation that uses a second write period that is longer than the first write period.
19. The non-volatile solid-state device of claim 8 , wherein
a program verify operation associated with writing the first test data in the first region uses a first verification threshold voltage, and
a program verify operation associated with writing the user data in the first region uses a second verification threshold voltage that is lower than the first verification threshold.
20. The non-volatile solid-state device of claim 8 , wherein the test data includes a predetermined data test pattern or user data, or a combination of both.
21. The non-volatile solid-state device of claim 8 , the controller is further configured to store the second user data on a magnetic storage device associated with the non-volatile solid-state device.
22. The non-volatile solid-state device of claim 8 , wherein rewriting the second user data in the third region comprises writing the second user data in the third region as part of a garbage collection operation.