Apparatus, system and method for managing solid-state retirement

• US 9,251,019 B2
• Filed: 12/21/2012
• Issued: 02/02/2016
• Est. Priority Date: 05/29/2012
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: Losh, Warner, Peterson, James
• Primary Examiner(s): Bonzo, Bryce
• Assistant Examiner(s): Mehrmanesh, Elmira
• Application Number:
  US13/724,761
• Publication Number:
  US 20130326269A1
• Time in Patent Office: 1,138 Days
• Field of Search: 714/47.1, 714/47.2, 714/47.3, 714/6.1, 714/6.11, 714/6.13, 714/25, 714/42, 714/54
• US Class Current: 1/1
• CPC Class Codes: G06F 11/004 Error avoidance G06F11/07 and subgroups take precedence
• CPC Class Codes: G06F 11/1068 in sector programmable memories, e.g. flash disk G06F11/1072 takes precedence
• CPC Class Codes: G06F 11/108 Parity data distribution in semiconductor storages, e.g. in SSD
• CPC Class Codes: G06F 11/2053 where persistent mass storage functionality or persistent mass storage control functionality is redundant error detection or correction in information storage based on relative movement between record carrier and transducer G11B20/18
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/0607 Interleaved addressing
• CPC Class Codes: G06F 2211/109 Sector level checksum or ECC, i.e. sector or stripe level checksum or ECC in addition to the RAID parity calculation
• CPC Class Codes: G06F 2212/1036 Life time enhancement
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G06F 2212/7208 Multiple device management, e.g. distributing data over multiple flash devices
• CPC Class Codes: G06F 2212/7211 Wear leveling
• CPC Class Codes: G11C 16/3418 Disturbance prevention or evaluation; Refreshing of disturbed memory data
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles
• CPC Class Codes: G11C 2029/0409 Online test
• CPC Class Codes: G11C 29/82 for EEPROMs

Abstract

A storage controller is configured to determine a reliability metric of a storage division of a solid-state storage medium based on one or more test read operations. The storage division may be retired based on the reliability metric and/or the age of the data on the storage division. A storage division comprising aged data may be marked for post-write reliability testing, which may comprise determining a post-write reliability metric in response to grooming and/or reprogramming the storage division. The storage controller may project the reliability metric of the storage division to the end of a predetermined data retention period. Portions of a storage divisions that exhibit poor reliability may be removed to improve the reliability of the storage division without taking the entire storage division out of service.

Claims

1. An apparatus, comprising:

an age module configured to determine an age of data stored on a portion of a solid-state storage medium, wherein the age of the data corresponds to a time period that the data has been retained on the portion; and

a reliability module configured to determine whether to retire the portion based on a comparison between the determined age of the data and a time threshold,

wherein the reliability module is configured to determine whether to retire the portion by use of a first error threshold in response to the determined age of the data being less than the time threshold, and

wherein the reliability module is configured to determine whether to retire the portion by use of a second error threshold in response to the determined age of the data exceeding the time threshold, wherein the second error threshold differs from the first error threshold, and

wherein the age module and the reliability module compromise one of more of instructions stored on a non-transitory storage medium, a circuit, and a programmable circuit.

2. The apparatus of claim 1, further comprising a marking module configured to mark the portion for post-write reliability testing in response to the determined age of the data exceeding the time threshold and an error metric of the portion failing to satisfy the second error threshold.

3. The apparatus of claim 2, further comprising a groomer module configured to groom the marked portion of the solid-state storage medium.

4. The apparatus of claim 3, wherein the groomer module is configured to prioritize grooming the marked portion over grooming one or more other portions of the solid-state storage medium.

5. The apparatus of claim 2, further comprising a scan module configured to perform one or more test read operations on the marked portion of the solid-state storage medium in response to storing data on the marked portion, wherein the reliability module is configured to determine whether to retire the marked portion based on a post-write reliability metric of the marked storage division, the post-write reliability metric based on the one or more test read operations.

6. The apparatus of claim 5, further comprising a projection module configured to determine a projected reliability metric of the portion based on a data retention period, wherein the reliability module is configured to retire the marked portion of the solid-state storage medium in response to the projected reliability metric failing to satisfy a reliability threshold.

7. The apparatus of claim 6, wherein the time threshold is 24 hours and the data retention period is 90 days.

8. The apparatus of claim 6, wherein the reliability threshold is based on an error-correcting strength for data stored on the solid-state storage medium.

9. The apparatus of claim 1, wherein the portion comprises a storage division of the solid-state storage medium, the apparatus further comprising:

a scan module configured to perform one or more test read operations on the storage division according to a scan pattern, wherein the reliability module is configured to determine an error metric of the storage division based on the one or more test read operations,

wherein the reliability module is configured to determine whether to retire the portion by comparing the error metric to one or more of the first error threshold and the second error threshold.

10. The apparatus of claim 9, wherein the error metric comprises a raw bit error rate of the one or more test read operations on the storage division.

11. The apparatus of claim 1, wherein the portion comprises a plurality of erase blocks, the apparatus further comprising an accumulation module configured to determine an accumulated error metric of the portion based on respective error metrics of the erase blocks comprising the portion.

12. The apparatus of claim 11, wherein the reliability module is configured to retire one or more of the erase blocks of the portion in response to the accumulated error metric failing to satisfy one or more of the first error threshold and the second error threshold.

13. The apparatus of claim 12, wherein the reliability module is configured to select erase blocks of the portion to retire such that the accumulated error metric, derived from the error metrics of the remaining erase blocks of the portion, satisfies one or more of the first error threshold and the second error threshold.

14. A non-transitory machine-readable storage medium comprising instructions configured to cause a computing device to perform a method, the method comprising:

calculating a reliability metric of a storage division of a solid-state storage medium based on a read operation performed on the storage division;

marking the storage division for post-write reliability testing in response to a time differential between a time data was programmed to the storage division and a time the read operation was performed on the storage division exceeding a time threshold and the reliability metric failing to satisfy a reliability threshold; and

retiring the storage division in response to the time differential being less than the time threshold and the reliability metric failing to satisfy the reliability threshold.

15. The non-transitory machine-readable storage medium of claim 14, wherein calculating the reliability metric comprises projecting the reliability metric to an end of a data retention period, the method further comprising:

retiring the storage division in response to determining that the reliability metric projection fails to satisfy the reliability threshold and that the differential does not exceed the time threshold.

16. The non-transitory machine-readable storage medium of claim 14, the method further comprising performing post-write reliability testing on the storage division by:

reprogramming the storage division;

calculating a post-write reliability metric of the storage division based on one or more test read operations performed subsequent to reprogramming the storage division; and

retiring the storage division in response to the post-write reliability metric failing to satisfy a post-write reliability threshold.

17. The non-transitory machine-readable storage medium of claim 14, wherein marking the storage division for post-write reliability testing comprises storing a persistent note on the solid-state storage medium.

18. The non-transitory machine-readable storage medium of claim 14, wherein the storage division comprises a plurality of erase blocks, the method further comprising:

calculating an accumulated reliability metric of the storage division based on reliability metrics of the plurality of erase blocks comprising the storage division; and

retiring one or more of the erase blocks in response to the accumulated reliability metric failing to satisfy the reliability threshold.

19. A system, comprising:

means for calculating an estimated reliability metric of a storage division after a predetermined data retention period based on a current reliability metric of the storage division and a reliability model;

means for determining an age of data stored on the storage division, wherein the age of the data corresponds to a time that has elapsed since the data was programmed onto the storage division;

means for retiring the storage division in response to determining that the estimated reliability metric fails to satisfy a reliability threshold and the age of the data is within a time threshold; and

means for marking the storage division for post-write reliability testing in response to determining that the estimated reliability metric fails to satisfy the reliability threshold and the age of the data exceeds the time threshold,

wherein the means for calculating the estimated reliability metric, the means for determining an age of data stored on the storage division, the means for retiring the storage division, and the means for marking the storage division comprise one or more of instructions stored on a non-transitory storage medium, a circuit, and a programmable circuit.

20. The system of claim 19, wherein the means for determining the age of the data stored on the storage division comprises means for determining a time differential between a last programming time of the storage division and a time the current reliability metric was determined.