Process and Apparatus to Reduce Declared Capacity of a Storage Device by Altering an Encoding Format

• US 20160062663A1
• Filed: 02/12/2015
• Published: 03/03/2016
• Est. Priority Date: 09/02/2014
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: Samuels, Allen, Kruger, Warren Fritz, Truong, Linh Tien
• Granted Patent: US 9,524,105 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0238 Memory management in non-volatile memory, e.g. resistive RAM or ferroelectric memory
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/0253 Garbage collection, i.e. reclamation of unreferenced memory
• CPC Class Codes: G06F 2212/7204 Capacity control, e.g. partitioning, end-of-life degradation
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G06F 2212/7211 Wear leveling
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/0661 Format or protocol conversion arrangements
• CPC Class Codes: G06F 3/0688 Non-volatile semiconductor memory arrays
• CPC Class Codes: G11C 11/5621 using charge storage in a floating gate
• CPC Class Codes: G11C 16/00 Erasable programmable read-only memories G11C14/00 takes precedence
• CPC Class Codes: G11C 16/08 Address circuits; Decoders; Word-line control circuits
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles
• CPC Class Codes: G11C 2211/5641 Multilevel memory having cells with different number of storage levels

Abstract

Systems, methods and/or devices are used to reduce declared capacity of non-volatile memory of a storage device in a storage system. In one aspect, the method includes, detecting an amelioration trigger for reducing declared capacity of non-volatile memory of a storage device of the storage system, and in accordance with the detected amelioration trigger, performing an amelioration process to reduce declared capacity of the non-volatile memory of the storage device, the performing including: altering an encoding format of at least a portion of the non-volatile memory of the storage device, and reducing declared capacity of the non-volatile memory of the storage device. In some embodiments, the storage device includes one or more flash memory devices. In some embodiments, the detecting, the performing, or both are performed by the storage device, or by one or more subsystems of the storage system distinct from the storage device, or by the host.

Claims

1. A method of managing a storage system, the method comprising:

detecting an amelioration trigger for reducing declared capacity of non-volatile memory of a storage device of the storage system; and

in accordance with the detected amelioration trigger, performing an amelioration process to reduce declared capacity of the non-volatile memory of the storage device, the performing including;

altering an encoding format of at least a portion of the non-volatile memory of the storage device; and

reducing declared capacity of the non-volatile memory of the storage device.

2. The method of claim 1, further comprising:

prior to detecting the amelioration trigger, detecting a first wear condition of the non-volatile memory of the storage device, wherein a total storage capacity of the non-volatile memory of the storage device includes declared capacity and over-provisioning; and

in response to detecting the first wear condition, performing a remedial action that reduces over-provisioning of the non-volatile memory of the storage device without reducing declared capacity of the non-volatile memory of the storage device.

3. The method of claim 2, wherein detecting the amelioration trigger comprises detecting a second wear condition distinct from the first wear condition.

4. The method of claim 1, wherein the detecting, the performing, or both the detecting and the performing are performed by the storage device.

5. The method of claim 1, wherein the detecting, the performing, or both the detecting and the performing are performed by one or more subsystems of the storage system distinct from the storage device.

6. The method of claim 1, wherein the detecting, the performing, or both the detecting and the performing are performed by a host.

7. The method of claim 6, wherein the host includes a client on behalf of which data is stored in the storage system.

8. The method of claim 6, wherein the host includes a storage system controller of the storage system.

9. The method of claim 6, wherein the host includes a cluster controller of the storage system.

10. The method of claim 1, wherein altering the encoding format of at least a portion of the non-volatile memory of the storage device includes altering the encoding format of at least a portion of the non-volatile memory of the storage device in accordance with one or more parameters for the amelioration process.

11. The method of claim 1, wherein altering the encoding format of at least a portion of the non-volatile memory of the storage device includes altering the encoding format from a higher-density physical encoding format to a lower-density physical encoding format.

12. The method of claim 1, wherein altering the encoding format of at least a portion of the non-volatile memory of the storage device includes altering a number of states per memory cell from a higher number of states to a lower number of states.

13. The method of claim 1, wherein altering the encoding format of at least a portion of the non-volatile memory of the storage device includes altering the encoding format from a Triple-Level Cell (TLC) format to a Multi-Level Cell (MLC) format.

14. The method of claim 1, wherein altering the encoding format of at least a portion of the non-volatile memory of the storage device includes altering the encoding format from a Triple-Level Cell (TLC) format to a Single-Level Cell (SLC) format.

15. The method of claim 1, wherein altering the encoding format of at least a portion of the non-volatile memory of the storage device includes altering the encoding format from a Multi-Level Cell (MLC) format to a Single-Level Cell (SLC) format.

16. The method of claim 1, wherein performing the amelioration process to reduce declared capacity of the non-volatile memory of the storage device includes reducing utilization of the non-volatile memory of the storage device.

17. The method of claim 1, wherein altering the encoding format of at least a portion of the non-volatile memory of the storage device includes altering the encoding format of a memory portion of a plurality of memory portions of the non-volatile memory of the storage device.

18. The method of claim 1, wherein altering the encoding format of at least a portion of the non-volatile memory of the storage device includes altering the encoding format of all client data of the non-volatile memory of the storage device.

19. The method of claim 1, wherein performing the amelioration process to reduce declared capacity of the non-volatile memory of the storage device further includes advertising a reduced declared capacity of the non-volatile memory of the storage device.

20. The method of claim 1, further comprising:

after beginning performance of the amelioration process to reduce declared capacity of the non-volatile memory of the storage device, detecting an indication to abort the reduction in declared capacity of the non-volatile memory of the storage device;

in response to detecting the indication to abort the reduction in declared capacity of the non-volatile memory of the storage device, aborting performance of the amelioration process to reduce declared capacity of the non-volatile memory of the storage device.

21. The method of claim 1, wherein the storage device comprises one or more flash memory devices.

22. A storage device, comprising:

non-volatile memory;

one or more processors; and

controller memory storing one or more programs, which when executed by the one or more processors cause the storage device to perform operations comprising;

detecting an amelioration trigger for reducing declared capacity of the non-volatile memory of the storage device; and

in accordance with the detected amelioration trigger, performing an amelioration process to reduce declared capacity of the non-volatile memory of the storage device, the performing including;

altering an encoding format of at least a portion of the non-volatile memory of the storage device; and

reducing declared capacity of the non-volatile memory of the storage device.

23. The storage device of claim 22, wherein the one or more programs further include instructions that, when executed by the one or more processors, cause the storage device to perform operations comprising:

prior to detecting the amelioration trigger, detecting a first wear condition of the non-volatile memory of the storage device, wherein a total storage capacity of the non-volatile memory of the storage device includes declared capacity and over-provisioning; and

in response to detecting the first wear condition, performing a remedial action that reduces over-provisioning of the non-volatile memory of the storage device without reducing declared capacity of the non-volatile memory of the storage device.

24. A non-transitory computer readable storage medium, storing one or more programs configured for execution by one or more processors of a storage device, the one or more programs including instructions for:

detecting an amelioration trigger for reducing declared capacity of the non-volatile memory of the storage device; and

in accordance with the detected amelioration trigger, performing an amelioration process to reduce declared capacity of the non-volatile memory of the storage device, the performing including;

altering an encoding format of at least a portion of the non-volatile memory of the storage device; and

reducing declared capacity of the non-volatile memory of the storage device.

25. The non-transitory computer readable storage medium of claim 24, wherein the one or more programs further include instructions for:

prior to detecting the amelioration trigger, detecting a first wear condition of the non-volatile memory of the storage device, wherein a total storage capacity of the non-volatile memory of the storage device includes declared capacity and over-provisioning; and

in response to detecting the first wear condition, performing a remedial action that reduces over-provisioning of the non-volatile memory of the storage device without reducing declared capacity of the non-volatile memory of the storage device.