Write amplification reduction by delaying read access to data written during garbage collection

• US 9,235,509 B1
• Filed: 09/17/2013
• Issued: 01/12/2016
• Est. Priority Date: 08/26/2013
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Enterprise IP LLC (Western Digital Corporation)
• Inventors: Kankani, Navneeth, Kwong, Charles See Yeung
• Primary Examiner(s): Bradley, Matthew
• Assistant Examiner(s): Talukdar, Arvind
• Application Number:
  US14/029,655
• Time in Patent Office: 847 Days
• US Class Current: 1/1
• 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 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 2212/1016 Performance improvement
• CPC Class Codes: G06F 2212/1036 Life time enhancement
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control

Abstract

The various implementations described herein include systems, methods and/or devices used to enable write amplification reduction by delaying read access to data written during garbage collection. In one aspect, read access to a write unit to which data was written during garbage collection is delayed until a predefined subsequent operation has been completed.

Claims

1. A method of garbage collection in a storage system, the method comprising:

performing a garbage collection operation, including;

writing data, for the garbage collection operation, to a sequence of write units of a non-volatile storage medium block that was erased prior to writing data to the sequence of write units, including;

writing data to a first write unit of the storage medium block; and

after writing data to the first write unit, writing data to at least N write units of the storage medium block, the at least N write units of the storage medium block including a second write unit of the storage medium block, wherein N is a positive integer;

after writing data to the at least N write units,

enabling read access to the first write unit;

writing data to a subsequent write unit of the storage medium block; and

after writing data to the subsequent write unit, enabling read access to the second write unit.

2. The method of claim 1, further comprising deferring updating a translation table to point to the first write unit until after writing data to the at least N write units has been completed.

3. The method of claim 1, wherein the sequence of write units is on a sequence of word lines.

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

13. The method of claim 1, wherein N is at least two.

5. A device operable to perform garbage collection for a storage medium, the device comprising:

a storage medium interface for coupling the device to the storage medium; and

one or more modules, including a memory management module that includes one or more processors and memory storing one or more programs configured for execution by the one or more processors, the one or more modules coupled to the storage medium interface and configured to;

perform a garbage collection operation, including;

writing data, for the garbage collection operation, to a sequence of write units of a non-volatile storage medium block that was erased prior to writing data to the sequence of write units, including;

writing data to a first write unit of the storage medium block; and

after writing data to the first write unit, writing data to at least N write units of the storage medium block, the at least N write units of the storage medium block including a second write unit of the storage medium block, wherein N is a positive integer;

after writing data to the at least N write units,

enabling read access to the first write unit;

writing data to a subsequent write unit of the storage medium block; and

after writing data to the subsequent write unit, enabling read access to the second write unit.

6. The device of claim 5, wherein the one or more modules are further configured to defer updating a translation table to point to the first write unit until after writing data to the at least N write units has been completed.

7. The device of claim 5, wherein the sequence of write units is on a sequence of word lines.

8. The device of claim 5, wherein the storage medium comprises one or more flash memory devices.

14. The device of claim 5, wherein N is at least two.

9. A non-transitory computer readable storage medium storing one or more programs configured for execution by a device coupled to a storage medium, the one or more programs comprising instructions for causing the device to:

perform a garbage collection operation, including;

writing data, for the garbage collection operation, to a sequence of write units of a non-volatile storage medium block that was erased prior to writing data to the sequence of write units, including;

writing data to a first write unit of the storage medium block; and

after writing data to the first write unit, writing data to at least N write units of the storage medium block, the at least N write units of the storage medium block including a second write unit of the storage medium block, wherein N is a positive integer;

after writing data to the at least N write units,

enabling read access to the first write unit;

writing data to a subsequent write unit of the storage medium block; and

after writing data to the subsequent write unit, enabling read access to the second write unit.

10. The non-transitory computer readable storage medium of claim 9, wherein the one or more programs further include instructions that, when executed by the one or more processors, cause the device to defer updating a translation table to point to the first write unit until after the writing data to the at least N write units has been completed.

11. The non-transitory computer readable storage medium of claim 9, wherein the sequence of write units is on a sequence of word lines.

12. The non-transitory computer readable storage medium of claim 9, wherein the storage medium comprises one or more flash memory devices.

15. The non-transitory computer readable storage medium of claim 9, wherein N is at least two.