Solid state storage systems and methods for flexibly controlling wear leveling

• US 8,335,887 B2
• Filed: 12/29/2009
• Issued: 12/18/2012
• Est. Priority Date: 10/29/2009
• Status: Active Grant

• Current Assignee: Hynix Semiconductor Incorporated (SK Hynix Inc.)
• Original Assignee: Hynix Semiconductor Incorporated (SK Hynix Inc.)
• Inventors: Kim, Eui Jin, Kim, Kyeong Rho, Kim, Young Ho, Kwak, Jeong Soon
• Primary Examiner(s): Dudek, Jr., Edward
• Assistant Examiner(s): CHRZANOWSKI, MATTHEW R
• Application Number:
  US12/648,369
• Publication Number:
  US 20110107016A1
• Time in Patent Office: 1,085 Days
• Field of Search: None
• 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

Abstract

Solid-state storage systems and methods are provided for controlling a wear leveling process for uniform use of the memory cells that replaces worn memory blocks with less frequently used memory blocks. The wear leveling process is performed by changing the physical locations of the storage cells within each memory zone or plane. Reference values of target memory block erase counts and worn memory block erase counts are used for searching target memory blocks to be used as replacements.

Claims

1. A solid-state storage system comprising:

a buffer unit configured to load a partial of mapping pages, each of the mapping pages including a mapping information and an erase count corresponding to a memory block; and

a memory controller configured to search a target block based on an accumulated fail count which is a number of failure in searching a target block during a previous wear leveling process and an access count of the mapping pages, and configured to execute a wear leveling process replacing a worn block to the target block.

2. The solid state storage system according to claim 1, wherein the memory controller determines whether to execute the wear leveling process whenever data is erased.

3. The solid-state storage system according to claim 2, wherein the memory controller varies a number of the target block whenever a wear leveling process is executed.

4. The solid-state storage system according to claim 3, wherein the memory controller increases the accumulated fail count when searching of the target block fails and increases the number of the target block according to the increased accumulated fail count when a next wear leveling process is executed.

5. The solid-state storage system according to claim 2, wherein the memory controller increases the access count of the mapping pages and increases the number of the target block according to the increased access count of the mapping pages.

6. The solid-state storage system according to claim 5, wherein when an erase count of the worn block is larger than a previously set value, the memory controller increases the access count of the mapping pages.

7. The solid-state storage system according to claim 6, wherein as the access count of the mapping pages increases, the memory controller increases the number of mapping pages loaded into the buffer unit.

8. The solid-state storage system according to claim 7, wherein the mapping pages are loaded into the buffer unit sequentially.

9. The solid-state storage system according to claim 1, further comprising a flash memory area including a plurality of memory blocks, wherein the plurality of memory blocks includes the mapping pages.

10. A solid-state storage system comprising:

a flash memory area comprising memory blocks configured to store a mapping page in which mapping information and erase count of the memory blocks are stored; and

a memory controller configured to vary a number of a target block which is to replace a worn block among the memory blocks by using an accumulated fail count which is a number of failure in searching a target block and an access count of the mapping pages during a wear leveling process.

11. The solid-state storage system according to claim 10, wherein the memory controller increases the number of the target block in order to improve a searching success rate of the target block.

12. The solid-state storage system according to claim 11, wherein the memory controller increases the accumulated fail count when a searching of the target block fails during a previous wear leveling process.

13. The solid-state storage system according to claim 12, wherein the memory controller increases the access count of the mapping pages for increasing the number of the target block.

14. The solid-state storage system according to claim 10, wherein the memory controller decreases the accumulated fail count when a searching of the target block succeeds during a previous wear leveling process so as to decrease the number of the target block.

15. A method for controlling a solid-state storage system, comprising the steps of:

setting a first reference value according to an accumulated fail count which is a number of failure in searching a target block during a previous wear leveling process;

setting a second reference value according to an access count of mapping pages;

setting a target block searching condition according to the first reference value and the second reference value; and

searching a target block which is to replace a worn block based on the target block searching condition during a wear leveling process.

16. The method according to claim 15, wherein the target block searching condition is varied whenever the accumulated fail count increases.

17. The method according to claim 16, wherein a number of blocks to be searched as the target block is increased according to the varied target block searching condition.

18. The method according to claim 15, wherein the target block searching condition is varied whenever the access count of mapping pages increases.

19. The method according to claim 18, wherein the access count of mapping pages is increased when an erase count of the worn block exceeds a sum of an average erase count and an error range.

20. The method according to claim 19, wherein a number of blocks to be searched as the target block is increased according to the varied target block searching condition.