Non-volatile memory management system with time measure mechanism and method of operation thereof

• US 9,063,844 B2
• Filed: 08/30/2012
• Issued: 06/23/2015
• Est. Priority Date: 09/02/2011
• Status: Expired due to Fees

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Smart Storage Systems Incorporated (Western Digital Corporation)
• Inventors: Higgins, James, Fitzpatrick, James, Dancho, Mark
• Primary Examiner(s): Savla, Arpan P.
• Assistant Examiner(s): WOOLWINE, SHANE D
• Application Number:
  US13/599,241
• Publication Number:
  US 20130060994A1
• Time in Patent Office: 1,027 Days
• Field of Search: 711/103, 711/105, 711/106, 711/136, 711/158, 711/160, 711/170, 711/115, 711/165, 711/E12.002, 714/16, 714/E11.117, 707/737, 707/E17.089, 710/36, 713/1, 365/45, 365/189.001, 365/185.33
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G06F 3/0644 Management of space entities, e.g. partitions, extents, pools

Abstract

A method of operation of a non-volatile memory management system includes: selecting a specific time period by a unit controller; establishing a first time pool having super blocks written during the specific time period; and promoting to a second time pool, the super blocks from the first time pool, at the lapse of the specific time period.

Claims

1. A method of operation of a non-volatile memory system having a set of memory blocks, the method comprising:

establishing an ordered set of time pools, including at least three distinct time pools, ordered with respect to data age of data in memory blocks assigned to the respective time pools, the time pools including a first, youngest time pool, a second, next youngest time pool, and an Nth, oldest time pool;

assigning memory blocks with newly written data to the first time pool;

at first predefined times, reassigning blocks in each time pool other than the Nth time pool to a next, older time pool; and

at second predefined times, determined with respect to data age of data in the memory blocks assigned to the Nth time pool, recycling data in the memory blocks assigned to the Nth time pool, including copying the recycled data to respective memory blocks, and assigning the respective memory blocks to the first time pool.

2. The method as claimed in claim 1, including:

establishing a data retention recycling threshold, and

in accordance with a determination that the data age of data in the memory blocks assigned to the Nth time pool is greater than the data retention recycling threshold, recycling data in the memory blocks assigned to the Nth time pool.

3. The method as claimed in claim 1 further comprising:

determining the data age of data in memory blocks assigned to each respective time pool of the ordered set of time pools in accordance with both passage of time and at least one operational characteristic of the non-volatile memory system selected from the set consisting of temperature, operating voltage and read/write disturbs.

4. The method as claimed in claim 1 wherein:

reassigning blocks in each time pool other than the Nth time pool to a next, older time pool includes updating contents of a system control random access memory, wherein the updated contents associate with the second time pool a set of memory blocks previously associated by the contents with the first time pool.

5. The method as claimed in claim 1, wherein the memory blocks assigned to the respective time pools are super blocks, each super block comprising a plurality of erase blocks.

6. The method of claim 1, wherein operation of a non-volatile memory management system comprising:

establishing the ordered set of time pools includes generating an index address having an age measurement segment for a respective time pool.

8. The method as claimed in claim 1, wherein the first predefined times comprise a sequence of times separated by respective time periods, and

wherein each of the respective time periods corresponds to an instance of a specific time period determined in accordance with at least one operational characteristic of the non-volatile memory system selected from the set consisting of capacity and write/read frequency.

9. The method as claimed in claim 1 further comprising:

storing information corresponding to assignments of the memory blocks to respective time pools, and

upon restoring power to the non-volatile memory system after a loss of power,

restoring the stored information corresponding to the assignments of the memory blocks to respective time pools; and

adjusting the data age of data in the memory blocks assigned to the respective time pools in accordance with the loss of power.

10. The method as claimed in claim 2, further comprising adjusting the data retention recycling threshold in accordance with at least one operational characteristic of the non-volatile memory system selected from the set consisting of voltage and temperature.

11. The method as claimed in claim 2, including:

establishing a data corruption threshold which is greater than the data retention recycling threshold, and

in accordance with a determination that the data age of data in the memory blocks assigned to the Nth time pool is greater than the data retention recycling threshold and less than the data retention recycling threshold, recycling data in the memory blocks assigned to the Nth time pool.

7. A non-volatile memory system comprising:

a unit controller and a memory controller coupled to the unit controller;

a threshold sensor coupled to the unit controller;

a non-volatile memory array coupled to the memory controller; and

a system control random access memory, coupled to the memory controller;

wherein the unit controller and memory controller are configured to;

establish an ordered set of time pools, including at least three distinct time pools, ordered with respect to data age of data in memory blocks assigned to the respective time pools, the time pools including a first, youngest time pool, a second, next youngest time pool, and an Nth, oldest time pool;

assign memory blocks with newly written data to the first time pool;

at first predefined times, reassign blocks in each time pool other than the Nth time pool to a next, older time pool; and

at second predefined times, determined with respect to data age of data in the memory blocks assigned to the Nth time pool, recycle data in the memory blocks assigned to the Nth time pool, including copying the recycled data to respective memory blocks, and assigning the respective memory blocks to the first time pool.

12. The system as claimed in claim 7, wherein the system is configured to:

establish a data retention recycling threshold, and

recycle data in the memory blocks assigned to the Nth time pool in accordance with a determination that the data age of data in the memory blocks assigned to the Nth time pool is greater than the data retention recycling threshold.

13. The system as claimed in claim 12, wherein the system is configured to:

adjust the data retention recycling threshold in accordance with at least one operational characteristic of the non-volatile memory system selected from the set consisting of voltage and temperature.

14. The system as claimed in claim 12, wherein the system is configured to:

establish a data corruption threshold which is greater than the data retention recycling threshold, and

recycle data in the memory blocks assigned to the Nth time pool in accordance with a determination that the data age of data in the memory blocks assigned to the Nth time pool is greater than the data retention recycling threshold and less than the data retention recycling threshold.

15. The system as claimed in claim 7, wherein the system is configured to:

determine the data age of data in memory blocks assigned to each respective time pool of the ordered set of time pools in accordance with both passage of time and at least one operational characteristic of the non-volatile memory system selected from the set consisting of temperature and operating voltage,

wherein the at least one operational characteristic is measured by the threshold sensor.

16. The system as claimed in claim 7, wherein the system is configured to:

update contents of the system control random access memory, wherein the updated contents associate with the second time pool a set of memory blocks previously associated by the contents with the first time pool.

17. The system as claimed in claim 7, wherein the memory blocks assigned to the respective time pools are super blocks, each super block comprising a plurality of erase blocks.

18. The system as claimed in claim 7, wherein the system is configured to:

generate an index address having an age measurement segment for a respective time pool.

19. The system as claimed in claim 7, wherein the first predefined times comprise a sequence of times separated by respective time periods, and

wherein each of the respective time periods corresponds to an instance of a specific time period determined in accordance with at least one operational characteristic of the non-volatile memory system selected from the set consisting of capacity and write/read frequency.

20. The system as claimed in claim 7, wherein the system is configured to:

store information corresponding to assignments of the memory blocks to respective time pools, and

upon restoring power to the non-volatile memory system after a loss of power,

restore the stored information corresponding to the assignments of the memory blocks to respective time pools; and

adjust the data age of data in the memory blocks assigned to the respective time pools in accordance with the loss of power.