Methods of sanitizing a flash-based data storage device

• US 20040188710A1
• Filed: 06/02/2003
• Published: 09/30/2004
• Est. Priority Date: 03/25/2003
• Status: Active Grant

• Current Assignee: Western Digital Israel Limited (Western Digital Corporation)
• Original Assignee: M-Systems Flash Disk Pioneers Ltd. (Western Digital Corporation)
• Inventors: Teicher, Mordechai, Koren, Rami, Leibinger, Eran, Tzur, Ofer, Aharonoff, Sagiv, Zilberman, Eugen, Wiesz, Nimrod
• Granted Patent: US 7,003,621 B2
• Time in Patent Office: Days
• US Class Current: 257/197
• CPC Class Codes: G06F 2221/2143 Clearing memory, e.g. to prevent the data from being stolen
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G11C 16/102 External programming circuits, e.g. EPROM programmers; In-circuit programming or reprogramming; EPROM emulators
• CPC Class Codes: G11C 16/105 Circuits or methods for updating contents of nonvolatile memory, especially with 'security' features to ensure reliable replacement, i.e. preventing that old data is lost before new data is reliably written
• CPC Class Codes: G11C 16/16 for erasing blocks, e.g. arrays, words, groups

Abstract

A data storage device includes one or more non-volatile, blockwise erasable data storage media and a mechanism for sanitizing the media in response to a single external stimulus or in response to a predetermined physical or logical condition. Optionally, only part of the media is sanitized, at a granularity finer than the blocks of the medium. Setting a flag in an auxiliary nonvolatile memory enables an interrupted sanitize to be detected and restarted. Optionally, a “death certificate” verifying the sanitizing is issued. Preferably, the media are configured in a manner that allows atomic operations of the sanitizing to be effected in parallel.

Claims

1. A method of cleaning a medium wherein data are stored, the medium including a plurality of blocks and that is only block-wise erasable, each block being bounded by a respective first block boundary and a respective second block boundary, the method comprising the steps of:

(a) selecting a portion of the medium to sanitize, said portion being bounded by a first portion boundary and a second portion boundary, at least one of said portion boundaries being within one of the blocks;

(b) for each of said portion boundaries that is within one of the blocks, copying the data, that is stored in said one block outside of said portion, to a second block; and

(c) sanitizing every block spanned by said portion.

2. The method of claim 1, wherein said second block is outside of said portion.

3. The method of claim 1, further comprising the step of:

(d) for each of said portion boundaries that is within said one block, sanitizing said second block prior to said copying to said second block.

4. The method of claim 1, further comprising the step of:

(d) sanitizing at least one free block that is outside of said portion.

15. The method of claim 11, further comprising the steps of:

(c) upon powering up the data storage medium, checking said flag; and

(d) if said flag is set, beginning a second sanitizing of the data storage medium.

16. The method of claim 15, further comprising the step of:

(e) upon completion of said second sanitizing, clearing said flag.

17. The method of claim 16, further comprising the steps of:

(f) before said beginning of said first sanitizing, saving at least one sanitize parameter.

18. The method of claim 17, further comprising the step of:

(g) upon completion of said second sanitizing, erasing said at least one sanitize parameter.

5. A data storage device comprising:

(a) a data storage medium; and

(b) a mechanism for sanitizing said data storage medium in response to a single external stimulus.

6. The data storage device of claim 5, wherein said mechanism includes an interface to a host system, and wherein said single external stimulus is a sanitize command.

7. The data storage device of claim 5, wherein said mechanism includes an interrupt handler and wherein said external stimulus is a hardware interrupt.

8. The data storage device of claim 7, further comprising:

(c) an interrupt initiator for providing said hardware interrupt.

9. The data storage device of claim 8, wherein said interrupt initiator includes a wireless transmitter and wherein said interrupt handler includes a wireless receiver.

10. The data storage device of claim 5, wherein said data storage medium is non-volatile.

11. A method of cleaning a data storage medium, comprising the steps of:

(a) setting a flag that indicates that the data storage medium is to be sanitized; and

(b) subsequent to said setting, beginning a first sanitizing of the data storage medium.

12. The method of claim 11, further comprising the step of:

(c) upon completion of said first sanitizing, clearing said flag.

13. The method of claim 12, further comprising the step of:

(d) before said beginning of said first sanitizing, saving at least one sanitize parameter.

14. The method of claim 13, further comprising the step of:

(e) upon completion of said first sanitizing, erasing said at least one sanitize parameter.

19. A data storage device comprising:

(a) a data storage medium; and

(b) a controller for sanitizing said data storage medium upon detection of a predetermined condition.

20. The data storage device of claim 19, wherein said condition is a physical condition.

21. The data storage device of claim 20, wherein said physical condition is an interruption of power.

22. The data storage device of claim 20, wherein said physical condition is an improper shutdown.

23. The data storage device of claim 19, wherein said condition is a logical condition.

24. The data storage device of claim 23, wherein said logical condition is indicative of an attempted unauthorized access of said data storage medium.

25. The data storage device of claim 23, wherein said logical condition is that a preselected datum stored in said data storage medium is accessed more than a predetermined number of times.

26. The data storage device of claim 23, wherein said logical condition is that a preselected portion of said data storage medium is accessed more than a predetermined number of times.

27. The data storage device of claim 19, wherein said data storage medium is a non-volatile data storage medium.

28. A method of cleaning a data storage medium, comprising the steps of:

(a) sanitizing the data storage medium; and

(b) subsequent to said sanitizing, setting a medium-is-sanitized flag.

29. The method of clam 28, further comprising the step of:

(c) verifying that said sanitizing has been effected.

30. The method of claim 29, wherein said verifying is effected by steps including:

(i) checking that said medium-is-sanitized flag is set.

31. The method of claim 30, wherein said verifying is effected by steps further including:

(ii) checking for a data pattern, stored in at least a portion of the data storage medium, that indicates that said sanitizing has been effected.

32. The method of claim 31, wherein said checking for said data is effected for all of the data storage medium.

33. The method of claim 29, further comprising the steps of:

(d) if said verifying determines that said sanitizing has been effected, issuing a death certificate for the data storage medium.

34. The method of claim 33, wherein said death certificate is based on a verification seed and on a serial number of a device that includes the data storage medium.

35. A data storage device comprising:

(a) at least one plurality of data storage media; and

(b) a controller for, for each said at least one plurality of said data storage media;

(i) writing data, substantially simultaneously, to at least a portion of each of said data storage media of said each plurality, and

(ii) erasing, substantially simultaneously, at least a portion of each of said data storage media of said each plurality.

36. The data storage device of claim 35, comprising at least two said pluralities of said data storage media.

37. The data storage device of claim 35, further comprising:

(c) for each said at least one plurality of said data storage media, at least one respective bus operationally connecting said data media of said each plurality to said controller.

38. The data storage device of claim 35, wherein said data storage media are non-volatile.

39. The data storage device of claim 38, wherein said data storage media are NAND flash chips.

40. The data storage device of claim 35, wherein each said data storage medium is page-wise writable, and wherein, when said data are written substantially simultaneously to said data storage media, each said portion of each said data storage medium, to which said data are written, is a single page of said each data storage medium.

41. The data storage device of claim 35, wherein each said data storage medium is page-wise writable, and wherein, when said data are written substantially simultaneously to said data storage media, each said portion of each said data storage medium, to which said data are written, is a plurality of pages of said each data storage medium.

42. The data storage device of claim 35, wherein, when said data are written substantially simultaneously to said data storage media, said data are written to all of each said data storage media.

43. The data storage device of claim 35, wherein each said data storage medium is block-wise erasable, and wherein, when said data storage media are erased substantially simultaneously, each said portion of each said data storage medium, that is erased, is a single block of said each data storage medium.

44. The data storage device of claim 35, wherein each said data storage medium is block-wise erasable, and wherein, when said data storage media are erased substantially simultaneously, each said portion of each said data storage medium, that is erased substantially simultaneously, is a plurality of blocks of said each data storage medium.

45. The data storage device of claim 35, wherein, when said data storage media are erased substantially simultaneously, all of each said data storage medium is erased.

46. A method of cleaning a data storage device that includes at least one plurality of data storage media, comprising the steps of:

(a) selecting a sanitize procedure, said sanitize procedure including at least one atomic operation; and

(b) for each at least one plurality of data storage media;

applying said selected sanitize procedure to the data storage media of said each plurality, with each said at least one atomic operation being applied substantially simultaneously to the data storage media of said each plurality.

47. The method of claim 46, wherein said at least one atomic operation is a write operation that writes data to a single page of each data storage medium.

48. The method of claim 46, wherein said at least one atomic operation is a write operation that writes data to a plurality of pages of each data storage medium.

49. The method of claim 46, wherein said at least one atomic operation is a write operation that writes data to all of each data storage medium.

50. The method of claim 46, wherein said at least one atomic operation is an erase operation that erases a single block of each data storage medium.

51. The method of claim 46, wherein said at least one atomic operation is an erase operation that erases a plurality of blocks of each data storage medium.

52. The method of claim 46, wherein said at least one atomic operation is an erase operation that erases all of each data storage medium.