Method and system for improving flash storage utilization by predicting bad M-pages

• US 10,339,001 B2
• Filed: 05/25/2017
• Issued: 07/02/2019
• Est. Priority Date: 09/30/2014
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Inventors: Tabrizi, Haleh, Agarwal, Rajiv, Ferreira, Jeffrey Paul, Bonwick, Jeffrey S., Shapiro, Michael W.
• Primary Examiner(s): Riad, Amine
• Application Number:
  US15/604,693
• Publication Number:
  US 20170262336A1
• Time in Patent Office: 768 Days
• CPC Class Codes: G06F 11/0727 in a storage system, e.g. in a DASD or network based storage system drivers for digital recording or reproducing units G06F3/06; circuits for error detection or correction within digital recording or reproducing units G11B20/18; for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS], H04L67/1097
• CPC Class Codes: G06F 11/076 by exceeding a count or rate limit, e.g. word- or bit count limit
• CPC Class Codes: G06F 11/1072 in multilevel memories
• CPC Class Codes: G06F 11/108 Parity data distribution in semiconductor storages, e.g. in SSD
• CPC Class Codes: G06F 11/2221 to test input/output devices or peripheral units
• CPC Class Codes: G06F 2212/403 Error protection encoding, e.g. using parity or ECC codes
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0653 Monitoring storage devices or systems
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G06F 3/0688 Non-volatile semiconductor memory arrays

Abstract

A method for managing persistent storage. The method includes selecting a page for a proactive read request, where the page is located in the persistent storage. The method further includes issuing the proactive read request to the page, receiving, in response to the proactive read request, a bit error value (BEV) for data stored on the page, obtaining a BEV threshold (T) for the page, wherein T is determined using a program/erase cycle value associated with the page and a retention time of the data stored on the page, making a first determination that the BEV is greater than T, based on the first determination: identifying an m-page, where the m-page is a set of pages and the page is in the set of pages, and setting the m-page as non-allocatable for future operations.

Claims

1. A method for managing persistent storage, the method comprising:

issuing, by a control module, a proactive read request to a page in the persistent storage;

receiving, in response to the proactive read request, a bit error value (BEV) for data stored on the page, wherein the BEV is based on a number of incorrect bits in the data;

obtaining, by the control module and based on at least one parameter associated with the page, a BEV threshold (T); and

based a determination that the BEV is greater than T, setting an m-page as non-allocatable for future operations, wherein the m-page is a set of pages in the persistent storage and the page is in the set of pages.

2. The method of claim 1, wherein future operations comprise at least one selected from a group consisting of a write operation and a garbage collection operation.

3. The method of claim 1, wherein the BEV specifies a percentage of bits in the page that are incorrect.

4. The method of claim 1, wherein the BEV specifies a number of bits in the page that are incorrect.

5. The method of claim 1, wherein the BEV is determined using error-correcting codes.

6. The method of claim 1, wherein the page is located on a solid-state memory module in the persistent storage, wherein the solid-state memory module comprises a multilevel cell (MLC).

7. The method of claim 1, wherein the at least one parameter associated with the page is retention time and wherein the retention time is determined using a first time that the data was written to the page and a second time associated with the proactive read request.

8. The method of claim 7, wherein the first time is obtained from an in-memory data structure in a memory, wherein the memory is located in the control module.

9. The method of claim 1, wherein the at least one parameter associated with the page is a P/E cycle value.

10. The method of claim 1, wherein future operations comprise at least one selected from a group consisting of a write operation and a garbage collection operation.

11. A system, comprising:

a storage module comprising a storage module controller and persistent storage; and

a control module operatively connected to the storage module and a client,

wherein the control module is programmed to;

issue, by the control module, a proactive read request to a page in the persistent storage;

receive, in response to the proactive read request, a bit error value (BEV) for data stored on the page, wherein the BEV is based on a number of incorrect bits in the data;

obtain, by the control module and based on at least one parameter associated with the page, a BEV threshold (T); and

based a determination that the BEV is greater than T, set an m-page as non-allocatable for future operations, wherein the m-page is a set of pages in the persistent storage and the page is in the set of pages.

12. The system of claim 11, wherein the persistent storage comprises flash memory and wherein the page is located in the flash memory.

13. The system of claim 11, wherein the BEV specifies a percentage of bits in the page that are incorrect.

14. The system of claim 11, wherein the BEV specifies a number of bits in the page that are incorrect.

15. The system of claim 11, wherein the BEV is determined using error-correcting codes.

16. The system of claim 11, wherein the page is located on a solid-state memory module in the persistent storage, wherein the solid-state memory module comprises a multilevel cell (MLC).

17. The system of claim 11, wherein the at least one parameter associated with the page is retention time and wherein the retention time is determined using a first time that the data was written to the page and a second time associated with the proactive read request.

18. The system of claim 17, wherein the first time is obtained from an in-memory data structure in a memory, wherein the memory is located in the control module.

19. The system of claim 11, wherein the at least one parameter associated with the page is a P/E cycle value and wherein the P/E cycle value is a P/E cycle value range.

20. A non-transitory computer readable medium comprising computer readable program code, which when executed by a computer processor enables the computer processor to:

issue, by a control module, a proactive read request to a page in persistent storage;

receive, in response to the proactive read request, a bit error value (BEV) for data stored on the page, wherein the BEV is based on a number of incorrect bits in the data;

obtain, by the control module and based on at least one parameter associated with the page, a BEV threshold (T); and

based a determination that the BEV is greater than T, set an m-page as non-allocatable for future operations, wherein the m-page is a set of pages in the persistent storage and the page is in the set of pages.