Sub-block garbage collection

• US 9,652,381 B2
• Filed: 06/20/2014
• Issued: 05/16/2017
• Est. Priority Date: 06/19/2014
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Inventors: Higgins, James M., Fitzpatrick, James, Dancho, Mark
• Primary Examiner(s): Rigol, Yaima
• Assistant Examiner(s): Sain, Gautam
• Application Number:
  US14/311,152
• Publication Number:
  US 20150370701A1
• Time in Patent Office: 1,061 Days
• Field of Search: 711103
• 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 2212/7205 Cleaning, compaction, garbage collection, erase control

Abstract

Systems, methods and/or devices are used to enable garbage collection of a sub-block of an individually erasable block of a storage medium in a storage device. In one aspect, the method includes determining a first trigger parameter in accordance with one or more operating conditions of a first sub-block of an erase block in the storage medium, and determining a second trigger parameter in accordance with one or more operating conditions of a second sub-block of the erase block in the storage medium. In accordance with a determination that the first trigger parameter meets a first vulnerability criterion, garbage collection of the first sub-block is enabled. Furthermore, in accordance with a determination that the second trigger parameter meets a second vulnerability criterion, garbage collection of the second sub-block is enabled.

Claims

1. A method of garbage collection for a storage medium in a storage device, the method comprising:

determining a first trigger parameter in accordance with one or more operating conditions of a first sub-block of a first erase block in the storage medium, the storage medium having a plurality of erase blocks that include the first erase block, where erase blocks are minimum size erasable units in the storage device and sub-blocks are sub-portions of corresponding erase blocks;

determining a second trigger parameter in accordance with one or more operating conditions of a second sub-block of the first erase block in the storage medium;

in accordance with a determination that the first trigger parameter meets a first vulnerability criterion, enabling sub-block garbage collection of the first sub-block; and

in accordance with a determination that the second trigger parameter meets a second vulnerability criterion, enabling sub-block garbage collection of the second sub-block, wherein the first vulnerability criterion is distinct from the second vulnerability criterion, wherein the first vulnerability criterion is a first read-disturb threshold and the second vulnerability criterion is a second read-disturb threshold, distinct from the first read-disturb threshold, and wherein sub-block garbage collection of a particular sub-block of the first erase block is distinct from garbage collection of the first erase block, and sub-block garbage collection of the particular sub-block of the first erase block includes;

writing a copy of valid data from the particular sub-block to a second erase block in the storage medium, wherein the second erase block is distinct from the first erase block; and

invalidating the particular sub-block in the first erase block.

2. The method of claim 1, wherein the first sub-block is a portion of the first erase block and the second sub-block is another portion of the first erase block.

3. The method of claim 1, wherein the first vulnerability criterion is determined in accordance with one or more characteristics of the first sub-block and the second vulnerability criterion is determined in accordance with one or more characteristics of the second sub-block.

4. The method of claim 1, wherein sub-block garbage collection of the first sub-block is performed prior to sub-block garbage collection of the second sub-block.

5. The method of claim 1, further comprising:

in accordance with the determination that the first trigger parameter meets the first vulnerability criterion, enabling sub-block garbage collection for a parity stripe that includes the first sub-block, wherein the parity stripe includes a plurality of sub-blocks across a plurality of erase blocks in the storage medium.

6. The method of claim 1, wherein enabling sub-block garbage collection of the first sub-block includes enabling sub-block garbage collection of the first sub-block in accordance with the determination that the first trigger parameter meets the first vulnerability criterion and a determination that the first erase block or a memory portion that includes the first erase block meets predefined age criteria.

7. A method of garbage collection for a storage medium in a storage device, the method comprising:

determining a first trigger parameter in accordance with one or more operating conditions of a first sub-block of a first erase block in the storage medium, the storage medium having a plurality of erase blocks that include the first erase block, where erase blocks are minimum size erasable units in the storage device and sub-blocks are sub-portions of corresponding erase blocks;

in accordance with a determination that the first trigger parameter meets a first vulnerability criterion, enabling sub-block garbage collection of the first sub-block, wherein the first vulnerability criterion includes a first read-disturb threshold for the first sub-block;

subsequent to enabling sub-block garbage collection of the first sub-block, determining whether the first erase block meets predefined garbage collection scheduling criteria, wherein the garbage collection scheduling criteria is distinct from the first vulnerability criterion and includes a criterion with respect to amount of valid data remaining in the first erase block; and

in accordance with a determination that the first erase block meets said garbage collection scheduling criteria, enabling garbage collection of the first erase block, wherein garbage collection of the first erase block is distinct from sub-block garbage collection of the first sub-block.

8. The method of claim 7, wherein sub-block garbage collection of the first sub-block comprises:

writing a copy of valid data from the first sub-block to a second erase block in the storage medium, wherein the second erase block is distinct from the first erase block; and

invalidating the first sub-block in the first erase block.

9. The method of claim 7, wherein the storage device comprises one or more flash memory devices.

10. The method of claim 7, wherein the storage device comprises one or more three-dimensional (3D) memory devices and circuitry associated with operation of memory elements in the one or more 3D memory devices.

11. The method of claim 10, wherein the circuitry and one or more memory elements in a respective 3D memory device, of the one or more 3D memory devices, are on the same substrate.

12. The method of claim 7, wherein garbage collection of the first erase block comprises:

writing a copy of valid data from the first erase block to an erase block, other than the first erase block, in the storage medium; and

invalidating the first erase block.

13. A storage device, comprising:

a non-transitory storage medium;

one or more processors; and

memory storing one or more programs to be executed by the one or more processors, the one or more programs comprising instructions for;

determining a first trigger parameter in accordance with one or more operating conditions of a first sub-block of a first erase block in the storage medium, the storage medium having a plurality of erase blocks that include the first erase block, where erase blocks are minimum size erasable units in the storage device and sub-blocks are sub-portions of corresponding erase blocks;

determining a second trigger parameter in accordance with one or more operating conditions of a second sub-block of the first erase block in the storage medium;

in accordance with a determination that the first trigger parameter meets a first vulnerability criterion, enabling sub-block garbage collection of the first sub-block; and

in accordance with a determination that the second trigger parameter meets a second vulnerability criterion, enabling sub-block garbage collection of the second sub-block, wherein the first vulnerability criterion is distinct from the second vulnerability criterion, wherein the first vulnerability criterion is a first read-disturb threshold and the second vulnerability criterion is a second read-disturb threshold, distinct from the first read-disturb threshold, and wherein sub-block garbage collection of a particular sub-block of the first erase block is distinct from garbage collection of the first erase block, and sub-block garbage collection of the particular sub-block of the first erase block includes;

writing a copy of valid data from the particular sub-block to a second erase block in the storage medium, wherein the second erase block is distinct from the first erase block; and

invalidating the particular sub-block in the first erase block.

14. The storage device of claim 13, wherein the first sub-block is a portion of the first erase block and the second sub-block is another portion of the first erase block.

15. The storage device of claim 13, wherein the first vulnerability criterion is determined in accordance with one or more characteristics of the first sub-block and the second vulnerability criterion is determined in accordance with one or more characteristics of the second sub-block.

16. The storage device of claim 13, wherein sub-block garbage collection of the first sub-block is performed prior to sub-block garbage collection of the second sub-block.

17. The storage device of claim 13, wherein the one or more programs further comprise instructions for enabling sub-block garbage collection for a parity stripe that includes the first sub-block, in accordance with the determination that the first trigger parameter meets the first vulnerability criterion, wherein the parity stripe includes a plurality of sub-blocks across a plurality of erase blocks in the storage medium.

18. The storage device of claim 13, wherein enabling sub-block garbage collection of the first sub-block include enabling sub-block garbage collection of the first sub-block in accordance with a determination that the first trigger parameter meets the first vulnerability criterion and a determination that the first erase block or a memory portion that includes the first erase block meets predefined age criteria.

19. A storage system, comprising:

a non-transitory storage medium;

one or more processors; and

memory storing one or more programs to be executed by the one or more processors, the one or more programs comprising instructions for;

determining a first trigger parameter in accordance with one or more operating conditions of a first sub-block of a first erase block in the storage medium, the storage medium having a plurality of erase blocks that include the first erase block, where erase blocks are minimum size erasable units in the storage device and sub-blocks are sub-portions of corresponding erase blocks;

in accordance with a determination that the first trigger parameter meets a first vulnerability criterion, enabling sub-block garbage collection of the first sub-block, wherein the first vulnerability criterion includes a first read-disturb threshold for the first sub-block;

subsequent to enabling sub-block garbage collection of the first sub-block, determining whether the first erase block meets predefined garbage collection scheduling criteria, wherein the garbage collection scheduling criteria is distinct from the first vulnerability criterion and includes a criterion with respect to amount of valid data remaining in the first erase block; and

in accordance with a determination that the first erase block meets said garbage collection scheduling criteria, enabling garbage collection of the first erase block, wherein garbage collection of the first erase block is distinct from sub-block garbage collection of the first sub-block.

20. The storage system of claim 19, wherein sub-block garbage collection of the first sub-block comprises:

writing a copy of valid data from the first sub-block to a second erase block in the storage medium, wherein the second erase block is distinct from the first erase block; and

invalidating the first sub-block in the first erase block.

21. The storage system of claim 19, wherein the storage medium comprises one or more flash memory devices.

22. The storage system of claim 19, wherein the storage medium comprises one or more three-dimensional (3D) memory devices and circuitry associated with operation of memory elements in the one or more 3D memory devices.

23. The storage system of claim 22, wherein the circuitry and one or more memory elements in a respective 3D memory device, of the one or more 3D memory devices, are on the same substrate.

24. The storage system of claim 19, wherein garbage collection of the first erase block comprises:

writing a copy of valid data from the first erase block to an erase block, other than the first erase block, in the storage medium; and

invalidating the first erase block.