Systems and methods for measuring the useful life of solid-state storage devices

• US 8,122,185 B2
• Filed: 01/15/2010
• Issued: 02/21/2012
• Est. Priority Date: 05/08/2006
• Status: Active Grant

• Current Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Original Assignee: SiliconSystems, Inc. (Western Digital Corporation)
• Inventors: Merry, David E. Jr., Diggs, Mark S., Drossel, Gary A.
• Primary Examiner(s): Bataille, Pierre-Michel
• Assistant Examiner(s): Fishburn, John P
• Application Number:
  US12/688,815
• Publication Number:
  US 20100122200A1
• Time in Patent Office: 767 Days
• Field of Search: None
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/1036 Life time enhancement
• CPC Class Codes: G06F 2212/7211 Wear leveling
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles
• CPC Class Codes: G11C 16/3495 Circuits or methods to detect or delay wearout of nonvolatile EPROM or EEPROM memory devices, e.g. by counting numbers of erase or reprogram cycles, by using multiple memory areas serially or cyclically

Abstract

A non-volatile solid-state storage subsystem, such as a non-volatile memory device, maintains usage statistics reflective of the wear state, and thus the remaining useful life, of the subsystem'"'"'s memory array. A host system reads the usage statistics information, or data derived therefrom, from the subsystem to evaluate the subsystem'"'"'s remaining life expectancy. The host system may use this information for various purposes, such as to (a) display or report information regarding the remaining life of the subsystem; (b) adjust the frequency with which data is written to the subsystem; and/or (c) select the type(s) of data written to the subsystem.

Claims

1. A data storage system in combination with a host system, comprising:

a storage subsystem that connects to and stores data for the host system, the storage subsystem comprising;

a memory array comprising a plurality of solid-state memory devices, each device having one or more data blocks; and

a controller configured to maintain usage data in the memory array with timestamp data, the usage data reflecting the number of times the one or more data blocks have been erased;

wherein the host system is configured with;

a first program module configured to;

retrieve said usage data with timestamp data, said usage data being from two or more different time periods; and

calculate an estimate of remaining useful life of the storage subsystem with the retrieved usage data from two or more different time periods; and

a second program module configured to generate a graphical display indicating said estimated remaining useful life of the storage subsystem.

2. The system of claim 1, wherein the display is configured as a meter that indicates a utilization of the storage subsystem relative to a percentage scale.

3. The system of claim 2, wherein the percentage scale corresponds to a specified endurance of the storage subsystem.

4. The system of claim 2, wherein the meter is configured to provide indicia of a threshold relative to the percentage scale.

5. The system of claim 4, wherein the threshold is less than the specified endurance of the storage subsystem.

6. The system of claim 2, wherein the meter is configured to provide indicia of a time displayed relative to the percentage scale so as to indicate how much of the storage subsystem has been utilized relative to the percentage scale during a predetermined time period.

7. The system of claim 1, wherein the display is configured as a bar chart that indicates a utilization of the storage subsystem relative to a percentage scale.

8. The method of claim 1 wherein said usage data comprise a first set of usage data that is specific to a first period of usage and a second set of usage data that is specific to a second period of usage that is separate from the first period.

9. A non-transitory computer-readable medium having stored thereon a computer program which, when executed by a host computer, causes the host computer to:

retrieve usage information from a solid state storage subsystem that is configured to maintain such usage information in a non-user-data memory area of the solid state storage subsystem, the usage information being reflective of a number of erase cycles that have been executed by the solid state storage subsystem; and

determine an estimated value of the remaining useful life based on said usage information; and

select a type of data to be written to the solid state storage subsystem based on the criticality of the data and the estimated value of the remaining useful life, wherein critical data is written to the solid state storage subsystem when the estimated value of the remaining useful life is above a threshold value.

10. The computer-readable medium of claim 9, wherein the computer program further causes the host computer to use said usage information to generate a graphical display depicting a remaining useful life of the solid state storage subsystem, the display including an indicia of an estimated value of the remaining useful life calculated from said usage information.

11. The computer-readable medium of claim 9, wherein the computer program further causes the host computer to use said usage information to vary a frequency with which data is written to the solid state storage subsystem.

12. The computer-readable medium of claim 11, wherein the computer program further causes the host computer to reduce the frequency with which data is written to the solid state storage subsystem when the estimated value of the remaining useful life falls below a threshold value.

13. The computer-readable medium of claim 9, wherein the usage information comprises a plurality of counter values indicating the number of times the plurality of blocks within the solid state storage subsystem have been erased, and the computer program is configured to use the counter values in combination to generate the estimated value of the remaining useful life of the solid state storage system.

14. A method of estimating a remaining useful life of a solid state storage subsystem, comprising:

maintaining a plurality of counter values in a plurality of memory blocks in the storage subsystem, wherein at least one counter value is associated with a single, particular memory block of the plurality of memory blocks and is incremented when the associated memory block is erased;

calculating, by storage subsystem, usage information reflective of a current wear level of the solid state storage subsystem based on the plurality of counter values;

storing the usage information with one or more timestamps; and

upon receiving a request from a host system, providing to the host system the usage information including the timestamps and data values derived from usage information obtained from two or more different time periods, the derived data values indicating the remaining useful life of the storage subsystem.

15. The method of claim 14 wherein the calculating further comprises:

adding the plurality of counter values to derive a sum of the counter values; and

dividing the sum of the counter values by a pre-determined threshold value, the threshold value being reflective of an estimated total number of erase cycles that can be performed in the life of the storage subsystem.

16. The method of claim 14 further comprising:

generating a graphical display depicting the remaining useful life of the storage subsystem, the display including an indicia of an estimated value of the remaining useful life calculated from the usage information.

17. The method of claim 14 further comprising:

selecting a type of data to be written to the storage subsystem based on the usage information.