Power Failure Detection And Correction In A Flash Memory Device

• US 20060179211A1
• Filed: 04/07/2006
• Published: 08/10/2006
• Est. Priority Date: 02/27/2002
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Kalkman, John, Aasheim, Jered Donald, Yang, Yongqi
• Granted Patent: US 7,350,105 B2
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: G06F 11/1435 using file system or storage system metadata
• CPC Class Codes: G06F 11/1441 Resetting or repowering
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/1474 in transactions G06F16/20 takes precedence
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: G06F 2212/7201 Logical to physical mapping or translation of blocks or pages
• CPC Class Codes: G06F 2212/7207 management of metadata or control data
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0643 Management of files
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99955 Archiving or backup

Abstract

A transactional file system developed to function with flash memory is described. The file system performs power-failure detection and ensures data integrity in the event of a power failure. In one described implementation, a power failure event can be detected by a file system, components of the file system, or individual modules in the form or computer-executable instructions and/or logic. Meta-information is stored at a location on a flash medium indicated by a write pointer if a computer device shuts-down according to a normal shutdown mode. During initialization of the computer, a check is performed whether the meta-information is present in the location on the flash medium indicated by the write pointer. If the meta-information is present, then a conclusion is made that the computer shutdown according to the normal shutdown mode.

Claims

1. In a computer that uses a flash medium to store data, a method for detecting a power failure, comprising:

storing meta-information at a location on a flash medium indicated by a write pointer if the computer shuts-down according to a normal shutdown mode;

during initialization of the computer, checking whether the meta-information is present in the location on the flash medium indicated by the write pointer;

concluding that the computer shutdown according to the normal shutdown mode if the meta-information is present; and

concluding that the computer did not shutdown according to the normal shutdown mode if the meta-information is not present.

2. The method as recited in claim 1, wherein the meta-information is a bit stored in a spare section of a physical sector of the flash medium.

3. The method as recited in claim 1, wherein the write pointer advances through physical sector addresses of the flash medium in a circular fashion.

4. The method as recited in claim 1, wherein the meta-information is a bit that is marked active each time the computer shuts-down according to the normal shutdown mode.

5. The method as recited in claim 1, wherein the meta-information is a bit that remains inactive if the computer does not shutdown according to the normal shutdown mode.

6. The method as recited in claim 1, wherein the location in the flash medium is a physical sector address.

7. The method as recited in claim 1, wherein the method is performed by a file system operating on a processor in the computer.

8. The method as recited in claim 1, wherein the method is performed by a software module operating on a processor in the computer.

9. One or more computer-readable media comprising computer executable instructions that, when executed, direct a computer to:

store meta-information at a location on a flash medium indicated by a write pointer if the computer shuts-down according to a normal shutdown mode;

during initialization of the computer, check whether the meta-information is present in the location on the flash medium indicated by the write pointer; and

conclude that the computer shutdown according to the normal shutdown mode if the meta-information is present.

10. One or more computer-readable media as recited in claim 9, further comprising computer executable instructions that, when executed, direct the computer to conclude that the computer did not shutdown according to the normal shutdown mode if the meta-information is not present.

11. One or more computer-readable media as recited in claim 9, wherein the write pointer advances through physical sector addresses of the flash medium in a circular fashion.

12. One or more computer-readable media as recited in claim 9, wherein the meta-information is a bit that is marked active each time the computer shuts-down according to the normal shutdown mode.

13. One or more computer-readable media as recited in claim 9, wherein the meta-information is a bit that remains inactive if the computer does not shutdown according to the normal shutdown mode.

14. One or more computer-readable media as recited in claim 9, wherein the location in the flash medium is a physical sector address.

15. One or more computer-readable media as recited in claim 9, wherein the computer executable instructions are components of a file system

16. A system for ensuring data integrity in a flash medium, comprising:

a write pointer configured to advance through a circular sequence of memory locations in the flash medium indicating a memory location that is free to receive data as the write pointer advances; and

a power failure manager configured to store metadata in the memory location indicated by the write pointer after completion of a write operation.

17. The system as recited in claim 16, wherein the power failure manager is further configured to search the memory location indicated by the write pointer for the metadata when the system is initialized.

18. The system as recited in claim 16, wherein the metadata is a bit in the memory location that is marked active at completion of the write operation.

19. The system as recited in claim 16, wherein the write pointer and power failure manager are components of a file system.

20. The system as recited in claim 16, further comprising a sector manager that maintains the write pointer and provides a next memory location address to store data upon receiving a write request, and further wherein the memory locations are physical sector addresses and the write pointer contains at least one counter that is incremented to advance the write pointer at least one memory location at a time at completion of a write operation.