PAGE-LEVEL HEALTH EQUALIZATION

• US 20160179664A1
• Filed: 12/23/2014
• Published: 06/23/2016
• Est. Priority Date: 12/23/2014
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Camp, Charles J., Mittelholzer, Thomas, Papandreou, Nikolaos, Parnell, Thomas, Pozidis, Charalampos
• Granted Patent: US 9,990,279 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 11/108 Parity data distribution in semiconductor storages, e.g. in SSD
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7201 Logical to physical mapping or translation of blocks or pages
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control

Abstract

According to one embodiment, a method includes assigning a subset of physical pages within a block of non-volatile memory to a pseudo-physical block, wherein a number of pages in the pseudo-physical block is less than a number of physical pages within the non-volatile memory block, and reassigning physical pages within the block of non-volatile memory to the pseudo-physical block upon occurrence of an event. The assigning includes: determining a health metric for each of the physical pages within the block of non-volatile memory, and selecting a subset of the physical pages for assignment to the pseudo-physical block based on the health metric. Moreover, the subset of pages has a fixed size for at least a number of reassignments.

Claims

1. A method, comprising:

assigning a subset of physical pages within a block of non-volatile memory to a pseudo-physical block, wherein a number of pages in the pseudo-physical block is less than a number of physical pages within the non-volatile memory block;

wherein the assigning includes;

determining a health metric for each of the physical pages within the block of non-volatile memory; and

selecting a subset of the physical pages for assignment to the pseudo-physical block based on the health metric;

reassigning physical pages within the block of non-volatile memory to the pseudo-physical block upon occurrence of an event;

wherein the subset of pages has a fixed size for at least a number of reassignments.

2. A method as recited in claim 1, wherein the non-volatile memory includes NAND Flash memory.

3. A method as recited in claim 1, wherein unused physical pages of the block which are not in the subset of pages are reassigned to pseudo-physical blocks in one or more of the at least a number of reassignments.

4. A method as recited in claim 1, comprising:

storing metadata associated with unused physical pages of the block which are not in the subset of pages.

5. A method as recited in claim 4, wherein the metadata includes a location of each of the unused physical pages within the block of non-volatile memory.

6. A method as recited in claim 4, wherein the metadata includes the health metrics of the associated unused physical pages.

7. A method as recited in claim 1, wherein reassigning the physical pages equalizes a health metric distribution of the block of non-volatile memory.

8. A method as recited in claim 1, wherein the health metric is a bit error rate.

9. A method as recited in claim 1, wherein the number of physical pages in the pseudo-physical block is 95% or more of the number of physical pages within the non-volatile memory block.

10. An apparatus, comprising:

non-volatile memory configured to store data; and

a controller and logic integrated with and/or executable by the controller, the logic being configured to;

assign a subset of physical pages within a block of the non-volatile memory to a pseudo-physical block, wherein a number of pages in the pseudo-physical block is less than a number of physical pages within the block of non-volatile memory;

wherein the assigning includes;

determine a health metric for each of the physical pages within the block of non-volatile memory; and

select a subset of the physical pages for assignment to the pseudo-physical block based on the health metric;

reassign physical pages within the block of non-volatile memory to the pseudo-physical block upon occurrence of an event;

wherein the subset of pages has a fixed size for at least a number of reassignments.

11. An apparatus as recited in claim 10, wherein the non-volatile memory includes NAND Flash memory.

12. An apparatus as recited in claim 10, wherein unused physical pages of the block which are not in the subset of pages are reassigned to pseudo-physical blocks in one or more of the at least a number of reassignments.

13. An apparatus as recited in claim 10, comprising:

storing metadata associated with unused physical pages of the block which are not in the subset of pages.

14. An apparatus as recited in claim 13, wherein the metadata includes a location of each of the unused physical pages within the block of non-volatile memory.

15. An apparatus as recited in claim 13, wherein the metadata includes the health metrics of the associated unused physical pages.

16. An apparatus as recited in claim 10, wherein reassigning the physical pages equalizes a health metric distribution of the block of non-volatile memory.

17. An apparatus as recited in claim 10, wherein the health metric is a bit error rate.

18. An apparatus as recited in claim 10, wherein the number of physical pages in the pseudo-physical block is 95% or more of the number of physical pages within the block of non-volatile memory.

19. A computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions readable and/or executable by a controller to cause the controller to:

assign, by the controller, a subset of physical pages within a block of non-volatile memory to a pseudo-physical block, wherein a number of pages in the pseudo-physical block is less than a number of physical pages within the non-volatile memory block;

wherein the assigning includes;

determine a health metric for each of the physical pages within the block of non-volatile memory; and

select a subset of the physical pages for assignment to the pseudo-physical block based on the health metric;

reassign, by the controller, physical pages within the block of non-volatile memory to the pseudo-physical block upon occurrence of an event;

wherein the subset of pages has a fixed size for at least a number of reassignments.

20. A computer program product as recited in claim 19, wherein unused physical pages of the block which are not in the subset of pages are reassigned to pseudo-physical blocks in one or more of the at least a number of reassignments.