WRITE-ERASE ENDURANCE LIFETIME OF MEMORY STORAGE DEVICES

• US 20110029715A1
• Filed: 07/29/2009
• Published: 02/03/2011
• Est. Priority Date: 07/29/2009
• Status: Active Grant

• Current Assignee: SK Hynix Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Hu, Xiao-yu, Haas, Robert, Eleftheriou, Evangelos S.
• Granted Patent: US 8,402,242 B2
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: B62D 35/001 For commercial vehicles or tractor-trailer combinations, e.g. caravans
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/1044 Space efficiency improvement
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G06F 2212/7211 Wear leveling
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles
• CPC Class Codes: G11C 16/3495 Circuits or methods to detect or delay wearout of nonvolatile EPROM or EEPROM memory devices, e.g. by counting numbers of erase or reprogram cycles, by using multiple memory areas serially or cyclically

Abstract

A memory management system and method for managing memory blocks of a memory device of a computer. The system includes a free block data structure including free memory blocks for writing, and sorting the free memory blocks in a predetermined order based on block write-erase endurance cycle count and receiving new user-write requests to update existing data and relocation write requests to relocate existing data separately, a user-write block pool for receiving youngest blocks holding user-write data (i.e., any page being updated frequently) from the free block data structure, a relocation block pool for receiving oldest blocks holding relocation data (i.e., any page being updated infrequently) from the free block data structure, and a garbage collection pool structure for selecting at least one of user-write blocks and relocation blocks for garbage collection, wherein the selected block is moved back to the free block data structure upon being relocated and erased.

Claims

1. A memory management system for a memory device of a computer, the system comprising:

a free block data structure including a plurality of free memory blocks for writing, the free block data structure configured to sort the free memory blocks in a predetermined order based on block write-erase endurance cycle count and receive new user-write requests to update existing data and relocation write requests to relocate existing data separately such that user-write data from new user-write requests are placed on youngest free memory blocks having lower block write-erase endurance cycle count while relocation data from relocation requests are placed on oldest free memory blocks having higher block write-erase endurance cycle count than that of the youngest free memory blocks,

a user-write data structure configured to receive user-write memory blocks holding the user-write data from the free block data structure;

a relocation data structure configured to receive relocation memory blocks holding the relocation data from the free block data structure; and

a garbage collection pool structure configured to select at least one of the user-write blocks and relocation blocks for erasure, wherein the selected block is moved to the free block data structure upon being erased.

2. The system of claim 1, wherein the user-write memory blocks in the user-write data structure have a highest remaining unconsumed remaining endurance cycle count and the relocation memory blocks in the relocation data structure have a lowest remaining unconsumed endurance cycle count.

3. The system of claim 1, wherein the selected block is selected for garbage collection based on a predetermined rule.

4. The system of claim 3, wherein the selected block is selected from a window of user-write memory blocks and a window of relocation memory blocks.

5. The system of claim 4, wherein a size of the window of the user-write memory blocks is equal to a size of the window of relocation memory blocks.

6. The system of claim 4, wherein a size of the window of the user-write memory blocks is unequal to a size of the window of relocation memory blocks.

7. A memory management system for a memory device of a computer, the system comprising:

a free block data structure including a plurality of free memory blocks for writing, the free block data structure is configured to sort the free memory blocks in a predetermined order based on block write-erase endurance cycle count and to receive new user-write requests to update existing data and relocation write requests to relocate existing data such that user-write data from new user-write requests are placed on youngest free memory blocks having lower block write-erase endurance cycle count while relocation data from relocation requests are placed on oldest free memory blocks having higher block write-erase endurance cycle count than that of the youngest free memory blocks;

a delay block data structure configured to receive memory blocks holding the user-write data and memory blocks holding the relocation data from the free block data structure and delay the memory blocks from being immediately selected as a candidate for garbage collection; and

a garbage collection pool structure configured to receive memory blocks from the delay block data structure, and select at least one of the memory blocks for erasure, wherein the selected memory block is moved to the free block data structure upon being erased.

8. The system of claim 7, wherein the delay block data structure is a first in first out (FIFO) queue.

9. The system of claim 8, wherein either a memory block holding user-write pages or a memory block holding relocation data pages is received at one side of the delay block data structure, and either a memory block holding user-write pages or a memory block holding relocation data pages is pushed out of the delay block data structure at an opposite side of the delay block data structure and into the garbage collection pool structure.

10. A computer-implemented method of managing memory blocks within a memory device, the method comprising:

maintaining free memory blocks for writing in a predetermined order based on block write-erase endurance cycle count and receiving new user-write requests to update existing data and relocation write requests to relocate existing data;

placing user-write data from the new user-write requests on youngest free memory blocks having lower block write-erase endurance cycle count;

placing relocation data from the relocation write requests on oldest free memory blocks having higher block write-erase endurance cycle counter than that of the youngest free memory blocks;

maintaining user-write memory blocks holding the user-write data and relocation memory blocks holding the relocation data; and

selecting at least one of the user-write memory blocks or the relocation memory blocks for erasure.

11. The computer-implemented method of claim 10, wherein selecting at least one of the user-write memory blocks or the relocation memory blocks comprises:

selecting at least one memory block from a window of user-write memory blocks and a window of relocation memory blocks, which are managed separately.

12. The computer-implemented method of claim 10, wherein selecting at least one of the user-write memory blocks or the relocation memory blocks comprises:

selecting at least one memory block from a window formed by a combination of user-write memory blocks and relocation memory blocks.

13. The computer-implemented method of claim 11, wherein a size of the window of the user-write memory blocks is equal to a size of the window of relocation memory blocks.

14. The computer-implemented method of claim 11, wherein a size of the window of the user-write memory blocks is unequal to a size of the window of relocation memory blocks.

15. A computer program product comprising a computer useable medium including a computer readable program, wherein the computer readable program when executed on a computer causes the computer to implement a method for managing memory blocks within a memory device, the method comprising:

maintaining free memory blocks for writing in a predetermined order based on block write-erase endurance cycle count and receiving new user-write requests to update existing data and relocation write requests to relocate existing data;

placing user-write data from the new user-write requests on youngest free memory blocks having lower block write-erase endurance cycle count;

placing relocation data from the relocation write requests on oldest free memory blocks having higher block write-erase endurance cycle count than that of the youngest free memory blocks;

maintaining user-write memory blocks holding the user-write data and relocation memory blocks holding the relocation data; and

selecting at least one of the user-write memory blocks or the relocation memory blocks for erasure.

16. The computer program product of claim 15, wherein selecting at least one of the user-write memory blocks or the relocation memory blocks comprises:

selecting at least one memory block from a window of user-write memory blocks and a window of relocation memory blocks, which are managed separately.

17. The computer program product of claim 15, wherein selecting at least one of the user-write memory blocks or the relocation memory blocks comprises:

selecting at least one memory block from a window formed by a combination of user-write memory blocks and relocation memory blocks.

18. The computer program product of claim 16, wherein a size of the window of the user-write memory blocks is equal to a size of the window of relocation memory blocks.

19. The computer program product of claim 16, wherein a size of the window of the user-write memory blocks is unequal to a size of the window of relocation memory blocks.