System and method for early detection of failure of a solid-state data storage system

• US 20050044454A1
• Filed: 09/17/2004
• Published: 02/24/2005
• Est. Priority Date: 12/22/2000
• Status: Active Grant

• Current Assignee: Innovative Memory Systems, Inc. (Wi-LAN Inc.)
• Original Assignee: Simpletech, Inc. (Western Digital Corporation)
• Inventors: Moshayedi, Mark
• Granted Patent: US 8,065,492 B2
• Time in Patent Office: Days
• US Class Current: 714/54
• CPC Class Codes: G06F 11/004 Error avoidance G06F11/07 and subgroups take precedence
• 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 11/073 in a memory management context, e.g. virtual memory or cache management memory management G06F12/00; testing of static memory units G11C29/00
• CPC Class Codes: G06F 11/076 by exceeding a count or rate limit, e.g. word- or bit count limit
• CPC Class Codes: G06F 11/2094 Redundant storage or storage space G06F11/2056 takes precedence

Abstract

Various embodiments are disclosed of a failure detection system for a solid-state data storage system that can experience difficulties, such as system failure or loss of data integrity, when it runs out of spare storage locations. Spare storage locations can be used by a solid-state data storage system to replace storage locations that have become defective. In one embodiment, a count is kept of the available spare storage locations in a system, or sub-system, and when the amount of available spare locations drops to a threshold value, an action can be taken to avoid the consequences of an impending failure. In other embodiments, the available spare storage locations are monitored by keeping track of the percentage of initially available spare locations still remaining, by keeping track of the rate of new spare locations being used, or by other techniques. In various embodiments, the early failure detection system responds to detection of a possible impending failure by taking one or more of a variety of actions, including, for example, sending an alert notification, enabling additional storage capacity, copying portions of the data stored in the system to other secure storage locations, shutting the system down, and taking no action.

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40. An early failure detection method for a flash memory system that designates a quantity of storage locations as spare locations, the spare locations being assigned for use as alternate storage locations in the event that defects occur, the early failure detection method comprising:

tracking the total quantity of spare locations that are available on multiple memory cards;

evaluating the total quantity of spare locations available to determine if a threshold value has been reached; and

in the event that the total quantity of spare locations reaches the threshold value, taking a preemptive action to avert impending failure of the flash memory system.

41. A method of determining the usability of a solid-state storage device, wherein the solid-state storage device comprises storage locations and spare storage locations for use in the event a defect occurs in at least one of the storage locations, the method comprising predicting the usability of the solid-state storage device based on a total quantity of unused spare storage locations in the solid-state storage device.

42. The method of claim 41, wherein the act of predicting the usability of the solid-state storage device comprises determining whether the quantity of unused spare storage locations is less than a predetermined threshold amount.

43. The method of claim 41, wherein the act of predicting the usability of the solid-state storage device comprises comparing the amount of unused spare storage locations to an original amount of spare storage locations.

44. The method of claim 41, wherein the act of predicting the usability of the solid-state storage device comprises monitoring the frequency of the occurrence of defects.

45. The method of claim 41, wherein the act of predicting the usability of the solid-state storage device comprises monitoring the rate of change in the frequency of the occurrence of defects.

46. A method of monitoring the life expectancy of a solid-state memory device, wherein the solid-state storage device comprises spare storage locations for use in the event a defect occurs in other storage locations, the method comprising:

comparing the total number of available spare locations available in an array of flash memory cards with a predetermined threshold; and

performing an action when the total quantity of unused spare storage locations in the array of flash memory cards falls below the predetermined threshold, so as to avoid the consequences of the failure of the flash memory cards.

47. The method of claim 46, wherein the predetermined threshold is maintained by a controller in the solid-state memory device.

48. The method of claim 46, wherein the predetermined threshold is calculated based on the quantity of an initial number of spare storage locations available within the solid-state memory device.

49. The method of claim 46, wherein the predetermined threshold is based on the number of spare storage locations typically available within other solid-state memory devices similar to the solid-state memory device.

50. A flash memory device comprising:

a plurality of storage locations;

a plurality of spare storage locations;

a predetermined threshold value; and

processor circuitry configured to compare the number of available spare storage locations in the flash memory device with the predetermined threshold, and wherein the processor circuitry is further configured to perform an action when the total quantity of unused spare storage locations falls below the predetermined threshold.

51. The flash memory device of claim 50, wherein the flash memory device is a flash memory card.

52. The flash memory device of claim 50, wherein the flash memory device is a flash memory chip.

53. The flash memory device of claim 50, wherein the flash memory device is an array of flash memory cards.

54. The flash memory device of claim 50, wherein storage locations can be dynamically allocated as spare storage locations.

55. The flash memory device of claim 50, wherein the action performed by the processor circuitry allows for the use of other unused spare storage locations accessible by the flash memory device to serve as supplemental spare storage locations.

56. The flash memory device of claim 50, wherein the processor circuitry is further configures to evaluate the quantity of available spare storage locations by referring to a counter that is based on the number of times new spare storage locations are used.

57. The flash memory device of claim 50, wherein the processor circuitry is further configures to evaluate the quantity of available spare storage locations by evaluating available spare storage locations at predetermined time intervals.

58. The flash memory device of claim 50, wherein the processor circuitry is further configures to evaluate the quantity of available spare storage locations upon request by a host system.

59. A system for determining the usability of a solid-state storage device, wherein the solid-state storage device comprises spare storage locations for use in the event a defect occurs in other storage locations, the system comprising:

means for monitoring the number of available spare storage locations in multiple memory cards; and

means for performing an action when the quantity of unused spare storage locations in the multiple memory cards falls below a threshold amount, so as to avert the consequences of the potential failure of the solid-state storage device.