Write-erase endurance lifetime of memory storage devices

• US 8,402,242 B2
• Filed: 07/29/2009
• Issued: 03/19/2013
• Est. Priority Date: 07/29/2009
• Status: Active Grant

• Current Assignee: SK Hynix Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Hu, Xiao-yu, Eleftheriou, Evangelos S., Haas, Robert
• Primary Examiner(s): Rones, Charles
• Assistant Examiner(s): Faal, Baboucarr
• Application Number:
  US12/511,577
• Publication Number:
  US 20110029715A1
• Time in Patent Office: 1,329 Days
• Field of Search: 711/170, 711/E12.009, 711/133
• US Class Current: 711/165
• 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:

the memory device;

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, wherein the selected block is selected from a window comprising user-write memory blocks selected form the user-write data structure and relocation memory blocks selected from the relocation data structure, the window being of a size s+t, where s is a number of user-write memory blocks in the window and t is a number of relocation memory blocks in the window, s is a number of user-write memory blocks less than of the all user write memory blocks in the user-write data structure and t is a number of relocation memory blocks less than all of the relocation memory blocks in the relocation data structure.

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 1, wherein a size, s, of the window of the user-write memory blocks is equal to a size, t of the window of relocation memory blocks.

5. The system of claim 1, wherein a size, s of the window of the user-write memory blocks is unequal to a size, t of the window of relocation memory blocks.

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

the memory device;

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;

a user-write data structure configured to receive user-write memory blocks holding the user-write data from a first portion of the free block data structure corresponding to free memory blocks having a low write-erase endurance cycle count;

a relocation data structure configured to receive relocation memory blocks holding the relocation data from a second portion of the free block data structure corresponding to free memory blocks having a high write-erase endurance cycle count; and

a garbage collection pool structure configured to select at least one of the user-write blocks and relocation blocks for erasure and to transmit the selected block to the free block data structure upon being erased, wherein the selected block is selected from a window comprising user-write memory blocks selected form the user-write data structure and relocation memory blocks selected from the relocation data structure, the window being of a size s+t, where s is a number of user-write memory blocks in the window and t is a number of relocation memory blocks in the window, s is a number of user-write memory blocks less than of the all user write memory blocks in the user-write data structure and t is a number of relocation memory blocks less than all of the relocation memory blocks in the relocation data structure.

7. The system of claim 6, wherein the user-write data structure is configured to receive user-write memory blocks from free memory blocks having lowest block write-erase endurance cycle counts, and

the relocation data structure is configured to receive relocation memory blocks from free memory blocks having highest block write-erase endurance cycle counts.

8. The system of claim 6, wherein the free block data structure is configured to write data from new user-write requests to free memory blocks having lowest block write-erase endurance cycle counts, and

the free block data structure is configured to write data from relocation requests to free memory blocks having highest block write-erase endurance cycle counts.

9. The system of claim 6, wherein the user-write data structure and the relocation data structure are configured to store user-write memory blocks and relocation memory blocks, respectively, in order based on block write-erase endurance cycle count.

10. The system of claim 9, wherein the garbage collection pool structure is configured to select for erasure the at least one user-write blocks and relocation blocks having a lowest write-erase endurance cycle count among the user-write memory blocks and relocation memory blocks in the window.

11. The system of claim 9, wherein the garbage collection pool structure is configured to select for erasure from among the user-write memory blocks and relocation memory blocks in the window the at least one user-write blocks and relocation blocks based on an order in which the at least one user-write blocks and relocation blocks are received into the user-write data structure and the relocation data structure, respectively.

12. The system of claim 6, wherein the garbage collection pool structure is configured to adjust a ratio of user-write memory blocks, s relative to the relocation memory blocks, t, in the window based on a weight of a user-write workload.

13. The system of claim 6, wherein the selected block is selected based on a number of invalid data pages in the selected block, the endurance cycle count of the selected block, and a predetermined weight factor.

14. A computer-program product, comprising:

a processor; and

memory having stored thereon a computer program which, upon execution by the processor, performs a method comprising;

arranging with the processor a plurality of free memory blocks in a block data structure based on a block write-erase endurance cycle count of the plurality of flee memory blocks;

writing data from user-write data requests to free memory blocks having lowest block write-erase endurance cycle counts and storing resulting user-write data blocks in a user-write data structure;

writing data from relocation data requests to free memory blocks having highest block write-erase endurance cycle counts and storing resulting relocation data blocks in a relocation data structure; and

selecting for a garbage collection operation at least one of the user-write blocks and relocation blocks for erasure, wherein the selected block is selected from a window comprising user-write memory blocks selected form the user-write data structure and relocation memory blocks selected from the relocation data structure, the window being of a size s+t, where s is a number of user-write memory blocks in the window and t is a number of relocation memory blocks in the window, s is a number of user-write memory blocks less than of the all user write memory blocks in the user-write data structure and t is a number of relocation memory blocks less than all of the relocation memory blocks in the relocation data structure.

15. The computer program product of claim 14, further comprising storing the user-write memory blocks and relocation memory blocks in the user-write data structure and the relocation data structure, respectively, in order based on block write-erase endurance cycle count.

16. The computer program product of claim 14, wherein selecting for the garbage collection operation at least one of the user-write blocks and relocation blocks for erasure includes selecting for erasure from among the user-write memory blocks and relocation memory blocks in the window the at least one user-write blocks and relocation blocks based on an order in which the at least one user-write blocks and relocation blocks entered the user-write data structure and the relocation data structure, respectively.

17. The computer program product of claim 14, further comprising adjusting a ratio of user-write memory blocks relative to relocation memory blocks in the window based on a weight of a user-write workload.

18. The computer program product of claim 14, wherein the selected block is selected based on a number of invalid data pages in the selected block, the endurance cycle count of the selected block, and a predetermined weight factor.