Intra-block memory wear leveling

• US 8,495,281 B2
• Filed: 12/04/2009
• Issued: 07/23/2013
• Est. Priority Date: 12/04/2009
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Iliadis, Ilias, Antonakopoulos, Theodoros A., Pletka, Roman, Hu, Xiao-Yu, Cideciyan, Roy D.
• Primary Examiner(s): ELMORE, STEPHEN C
• Application Number:
  US12/630,991
• Publication Number:
  US 20110138103A1
• Time in Patent Office: 1,327 Days
• Field of Search: 711/103, 711/154, 365/185.33
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7211 Wear leveling
• CPC Class Codes: G06F 3/0616 in relation to life time, e.g. increasing Mean Time Between Failures [MTBF]
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]

Abstract

A method for intra-block wear leveling within solid-state memory subjected to wear, having a plurality of memory cells includes the step of writing to at least certain ones of the plurality of memory cells, in a non-uniform manner, such as to balance the wear of the at least certain ones of the plurality of memory cells within the solid-state memory, at intra-block level. For example, if a behavior of at least some of the plurality of memory cells is not characterized, then the method may comprise characterizing a behavior of at least some of the plurality of memory cells and writing to at least certain ones of the plurality of memory cells, based on the characterized behavior, and in a non-uniform manner.

Claims

1. A method for intra-block wear leveling within solid-state memory subjected to wear, and having a plurality of memory cells arranged in blocks, the method comprising the step of:

writing to at least certain ones of the plurality of memory cells within the solid-state memory, in a non-uniform manner, such as to balance the wear of the at least certain ones of the plurality of memory cells within the solid-state memory, at intra-block level;

providing a behavior of at least some of the plurality of memory cells within the solid-state memory;

wherein the step of writing comprises writing to at least certain ones of the plurality of memory cells within the solid-state memory based on the provided behavior of the at least some of the memory cells within the solid-state memory, thereby writing to the at least certain ones of the plurality of memory cells within the solid-state memory in a non-uniform manner.

2. The method of claim 1, wherein the step of providing further comprises:

if the behavior of at least some of the plurality of memory cells within the solid-state memory is not characterized, then characterizing the behavior of at least some of the plurality of memory cells within the solid-state memory.

3. The method of claim 2, wherein the behavior of the at least some of the plurality of memory cells within the solid-state memory comprises a susceptibility to an error occurrence of each of the at least some of the plurality of memory cells within the solid-state memory.

4. The method of claim 2, wherein characterizing a behavior of at least some of the plurality of memory cells within the solid-state memory further comprises uniformly writing to at least some of the plurality of memory cells within the solid-state memory arranged as pages within blocks of the plurality of memory cells, and monitoring for errors the at least some of the plurality of memory cells within the pages of the blocks that are uniformly written to.

5. The method of claim 1, wherein the solid-state memory comprises one of a flash memory, a phase-change memory and an EPROM.

6. A computer program product for intra-block wear leveling within solid-state memory, the computer program product comprising:

a non-transitory computer-readable storage medium having computer readable program code embodied therewith, the computer readable program code comprising;

computer readable program code configured to implement a method for intra-block wear leveling within solid-state memory subjected to wear, and having a plurality of memory cells arranged in blocks, the method comprising the step of;

writing to at least certain ones of the plurality of memory cells within the solid-state memory, in a non-uniform manner, such as to balance the wear of the at least certain ones of the plurality of memory cells within the solid-state memory, at intra-block level; and

providing a behavior of at least some of the plurality of memory cells within the solid-state memory;

wherein the step of writing comprises writing to at least certain ones of the plurality of memory cells within the solid-state memory based on the provided behavior of the at least some of the memory cells within the solid-state memory, thereby writing to the at least certain ones of the plurality of memory cells within the solid-state memory in a non-uniform manner.

7. The computer program product of claim 6, wherein the step of providing further comprises:

if the behavior of at least some of the plurality of memory cells within the solid-state memory is not characterized, then characterizing the behavior of at least some of the plurality of memory cells within the solid-state memory.

8. The computer program product of claim 7, wherein the behavior of the at least some of the plurality of memory cells within the solid-state memory comprises a susceptibility to an error occurrence of each of the at least some of the plurality of memory cells within the solid-state memory.

9. The computer program product of claim 7, wherein characterizing a behavior of at least some of the plurality of memory cells within the solid-state memory further comprises uniformly writing to at least some of the plurality of memory cells within the solid-state memory arranged as pages within blocks of the plurality of memory cells, and monitoring for errors the at least some of the plurality of memory cells within the pages of the blocks that are uniformly written to.

10. The computer program product of claim 7, wherein writing to at least certain ones of the plurality of memory cells within the solid-state memory based on the characterized behavior of the at least some of the memory cells within the solid-state memory further comprises writing to the at least certain ones of the plurality of memory cells according to a static non-uniform page write distribution in which an expected long-term wear of the plurality of memory cells arranged as pages within blocks is approximately similar, thereby resulting in bit error probabilities of the same order.

11. The computer program product of claim 7, wherein writing to at least certain ones of the plurality of memory cells within the solid-state memory based on the characterized behavior of the at least some of the memory cells within the solid-state memory further comprises writing to the at least certain ones of the plurality of memory cells according to a dynamic non-uniform page write distribution that is periodically defined based on updated error correction code statistics, such that an expected long-term wear of the at least certain ones of the plurality of memory cells is approximately similar, thereby resulting in bit error probabilities of the same order.

12. A system, comprising:

a computing network including a processing device in communication with one or more computer memory storage devices; and

the computing network further configured to implement a method for intra-block wear leveling within solid-state memory subjected to wear, and having a plurality of memory cells arranged in blocks, the method comprising the steps of;

writing to at least certain ones of the plurality of memory cells within the solid-state memory, in a non-uniform manner, such as to balance the wear of the at least certain ones of the plurality of memory cells within the solid-state memory, at intra-block level;

providing a behavior of at least some of the plurality of memory cells within the solid-state memory;

wherein the step of writing comprises writing to at least certain ones of the plurality of memory cells within the solid-state memory based on the provided behavior of the at least some of the memory cells within the solid-state memory, thereby writing to the at least certain ones of the plurality of memory cells within the solid-state memory in a non-uniform manner.

13. The system of claim 12, wherein in the method implemented by the computing network, the step of providing further comprises:

if the behavior of at least some of the plurality of memory cells within the solid-state memory is not characterized, then characterizing the behavior of at least some of the plurality of memory cells within the solid-state memory.

14. The system of claim 13, wherein the behavior of the at least some of the plurality of memory cells within the solid-state memory comprises a susceptibility to an error occurrence of each of the at least some of the plurality of memory cells within the solid-state memory.

15. The system of claim 13, wherein characterizing a behavior of at least some of the plurality of memory cells within the solid-state memory further comprises uniformly writing to at least some of the plurality of memory cells within the solid-state memory arranged as pages within blocks of the plurality of memory cells, and monitoring for errors the at least some of the plurality of memory cells within the pages of the blocks that are uniformly written to.

16. The system of claim 12, wherein the solid-state memory comprises one of a phase-change memory, an EPROM, and a flash memory having a plurality of NAND memory cells.

17. A solid-state memory, comprising:

a processor;

a plurality of memory cells, where the processor is further configured to implement a method for intra-block wear leveling of at least some of the plurality of memory cells, the method further including the steps of

writing to at least certain ones of the plurality of memory cells within the solid-state memory, in a non-uniform manner, such as to balance the wear of the at least certain ones of the plurality of memory cells within the solid-state memory, at intra-block level; and

providing a behavior of at least some of the plurality of memory cells within the solid-state memory;

wherein the step of writing comprises writing to at least certain ones of the plurality of memory cells within the solid-state memory based on the provided behavior of the at least some of the memory cells within the solid-state memory, thereby writing to the at least certain ones of the plurality of memory cells within the solid-state memory in a non-uniform manner.

18. The solid-state memory of claim 17, wherein in the method implemented by the processor, the step of providing further comprises:

if the behavior of at least some of the plurality of memory cells within the solid-state memory is not characterized, then characterizing the behavior of at least some of the plurality of memory cells within the solid-state memory.