Apparatus, system, and method for wear management

• US 9,063,874 B2
• Filed: 03/15/2013
• Issued: 06/23/2015
• Est. Priority Date: 11/10/2008
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: Zhong, Hao, Plasson, Ned D., Wood, Robert, Hyun, Jea Woong, Sun, Hairong
• Primary Examiner(s): KUDIRKA, JOSEPH R
• Application Number:
  US13/844,338
• Publication Number:
  US 20130232289A1
• Time in Patent Office: 830 Days
• Field of Search: 714/42, 714/47.1, 714/47.2, 711/103
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1008 in individual solid state devices G06F11/1004 takes precedence
• CPC Class Codes: G06F 11/108 Parity data distribution in semiconductor storages, e.g. in SSD
• CPC Class Codes: G06F 11/141 for bus or memory accesses
• CPC Class Codes: G06F 11/3034 where the computing system component is a storage system, e.g. DASD based or network based digital input from or digital output to record carriers G06F3/06; digital recording or reproducing G11B20/18; for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS], H04L67/1097
• CPC Class Codes: G06F 11/3055 Monitoring arrangements for monitoring the status of the computing system or of the computing system component, e.g. monitoring if the computing system is on, off, available, not available error or fault processing without redundancy G06F11/0703; error detection or correction by redundancy in data representation G06F11/08; error detection or correction by redundancy in operation G06F11/14; error detection or correction by redundancy in hardware G06F11/16
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• 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: G11C 16/04 using variable threshold transistors, e.g. FAMOS
• CPC Class Codes: G11C 16/3418 Disturbance prevention or evaluation; Refreshing of disturbed memory data
• CPC Class Codes: G11C 16/3422 Circuits or methods to evaluate read or write disturbance in nonvolatile memory, without steps to mitigate the problem
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles
• CPC Class Codes: G11C 16/3495 Circuits or methods to detect or delay wearout of nonvolatile EPROM or EEPROM memory devices, e.g. by counting numbers of erase or reprogram cycles, by using multiple memory areas serially or cyclically
• CPC Class Codes: G11C 2029/0411 Online error correction
• CPC Class Codes: G11C 2029/1208 Error catch memory
• CPC Class Codes: G11C 29/42 using error correcting codes [ECC] or parity check
• CPC Class Codes: G11C 29/82 for EEPROMs
• CPC Class Codes: G11C 29/832 with disconnection of faulty elements
• CPC Class Codes: G11C 29/88 with partially good memories

Abstract

A storage module is configured to determine a health metric of a storage division of a solid-state storage medium. The health metric may comprise a combination of factors, including, but not limited to: wear level, performance (e.g., program time, erase time, and the like), error rate, and the like. A wear level module may configure storage operations to reduce the wear rate of storage divisions having poor health metrics and/or heath metrics that are degrading more quickly than other storage divisions. Reducing wear rate may include deferring grooming operations, delaying use for storage operations, temporarily retiring the storage division, or the like. Storage divisions may be brought back into service at normal use rates in response determining that other portions of the storage media have been worn to the point that they exhibit similar health and/or reliability characteristics.

Claims

1. A method, comprising:

determining an average error rate of storage operations performed across a plurality of sections of a solid-state storage medium;

identifying a section of the solid-state storage medium having an error rate that differs from the determined average error rate by more than a threshold; and

managing storage operations performed on the solid-state storage medium such that a program count for the identified section diverges from a program count of other sections of the solid-state storage medium.

2. The method of claim 1, wherein managing the storage operations comprises relocating valid data from the identified section and deferring a reclamation operation on the identified section.

3. The method of claim 1, wherein managing the storage operations comprises identifying a storage request pertaining to cold data, and storing the cold data on the identified section.

4. The method of claim 1, further comprising indicating that the identified section is out-of-service.

5. The method of claim 4, further comprising indicating that the identified section is in service and available for storing data in response to determining that a differential between the error rate of the identified section and a new average error rate of the solid-state storage medium determined after performing a plurality of storage operations on the solid-state storage medium is within the threshold.

6. The method of claim 1, further comprising:

determining an updated average error rate of the solid-state storage medium subsequent to identifying the section; and

managing storage operations performed on the solid-state storage medium such that a usage rate of the identified section converges with a usage rate of the other sections of the solid-state storage medium in response to determining that the error rate of the identified section differs from the updated average error rate by less than the threshold.

7. The method of claim 1, further comprising:

recording data indicating that the identified section is a reduced wear section of the solid-state storage medium; and

accessing the recorded data to manage the storage operations performed on the solid-state storage medium.

8. The method of claim 7, further comprising recording the data on a non-volatile storage medium.

9. The method of claim 1, wherein the error rate of a section of the solid-state storage medium is based on one or more of a raw bit error rate of read operations performed on the section, a program time for writing data to the section, and an erase time of the section.

10. An apparatus, comprising:

a reliability analysis module configured to determine an aggregate bit error rate of a solid-state storage medium and to identify a storage division of the solid-state storage medium having a bit error rate that deviates from the aggregate bit error rate by more than a threshold; and

a wear management module configured to adapt storage operations performed on the solid-state storage medium to cause an erase count of the identified storage division to differ from erase counts of other storage divisions of the solid-state storage medium,

wherein each of the reliability analysis module and the wear management module comprise one or more of logic hardware and executable code, the executable code stored on a computer readable storage medium.

11. The apparatus of claim 10, further comprising a reliability monitoring module configured to determine bit error rates of storage divisions of the solid-state storage medium, wherein the storage division bit error rates are based on bit errors corresponding to operations performed on the storage divisions.

12. The apparatus of claim 10, further comprising a groomer module configured to prepare storage divisions for use by relocating valid data from the storage divisions and initializing the storage divisions, wherein the groomer module is configured to prepare the identified storage division for reuse by relocating valid data from the identified storage division and delaying initialization of the identified storage division.

13. The apparatus of claim 10, further comprising a log storage module configured to queue storage divisions for data storage operations, wherein the log storage module is configured to remove the identified storage division from the queue.

14. The apparatus of claim 13, wherein the log storage module is configured to queue the identified storage division in a reduced usage queue, and to schedule a storage operation on a storage division in the reduced usage queue in response to receiving a storage request pertaining to low-usage data.

15. The apparatus of claim 13, wherein the log storage module is configured to queue storage divisions in an ordered queue, the ordered queue comprising the identified storage division, wherein the log storage module is further configured to reorder the ordered queue such that the identified storage division is at an end of the ordered queue.

16. The apparatus of claim 10, wherein the reliability analysis module is configured to retire the identified storage division, and to remove the identified storage division from retirement in response to determining that a difference between the health metric of the identified storage division and an updated aggregate health metric corresponding to respective health metrics of the storage divisions of the solid-state storage medium is less than the threshold.

17. A system, comprising:

means for identifying a first set of a plurality of solid-state storage sections having storage error rates that differ from storage error rates of a second set of the plurality of solid-state storage sections by more than a threshold;

means for receiving requests to perform storage operations on the solid-state storage sections; and

means for varying usage of the plurality of solid-state storage sections in servicing the requests to modify usage of the first set of solid-state storage sections such that erase counts on the solid-state storage sections of the first set differ as compared to erase counts of solid-state storage sections in the second set.

18. The system of claim 17, further comprising means for determining storage error rates of the solid-state storage sections comprising means for monitoring one or more of bit error rates for read operations performed on the respective solid-state storage sections, bit error rates for program operations performed on the respective solid-state storage sections, program times of the respective solid-state storage sections, and erase times of the respective solid-state storage sections.

19. The system of claim 18, further comprising:

means for determining updated storage error rates of solid-state storage sections of the second set of storage sections; and

means for selecting a storage section for removal from the first set and inclusion in the second set in response to determining that a storage error rate of the selected storage section is within a deviation threshold of the updated storage error rates of the solid-state storage sections in the second set.

20. The system of claim 17, further comprising means for grooming solid-state storage sections for reuse comprising means for delaying reuse of solid-state storage sections in the first set.

21. The system of claim 17, further comprising means for queuing storage operations on the solid-state storage sections configured to prevent storage operations from being queued to the solid-state storage sections in the first set.