Memory wear control

• US 8,732,389 B2
• Filed: 06/23/2009
• Issued: 05/20/2014
• Est. Priority Date: 06/23/2009
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Feldman, Timothy Richard, Haines, Jonathan Williams, Cook, Brett Alan
• Primary Examiner(s): Savla, Arpan P.
• Assistant Examiner(s): LI, ZHUO H
• Application Number:
  US12/489,604
• Publication Number:
  US 20100325340A1
• Time in Patent Office: 1,792 Days
• Field of Search: 711/103, 711/100, 711/114, 711/154, 711/170, 711/E12.001, 711/E12.008, 711/113, 711/156, 711/206, 711/208, 710/8
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7211 Wear leveling
• CPC Class Codes: G06F 3/0616 in relation to life time, e.g. increasing Mean Time Between Failures [MTBF]
• 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]

Abstract

The disclosure is related to systems and methods of controlling wear of a memory. In a particular embodiment, a system is disclosed that comprises a memory and a performance governor circuit coupled to the memory. The performance governor circuit is adapted to control a wear of the memory as a function of time.

Claims

1. A system comprising:

a performance governor circuit adapted to connect to a memory and adapted to control a degree of wear of the memory as a function of at least one selected point in time by;

preventing the wear from exceeding a wear level specified by a wear versus time profile;

determining a wear effect of executing a new command to access the memory on a current memory wear by examining a computed wear value for the new command; and

controlling execution of the new command based on the determined wear effect and based on a smallest possible command completion time of the new command; and

wherein the performance governor circuit is further configured to determine whether the computed wear value will cause the current memory wear to exceed the wear versus time profile, and if the wear value will not cause the current memory wear to exceed the wear versus time profile within the smallest possible command completion time, then execute the command.

2. The system of claim 1, wherein the performance governor circuit is adapted to control a degree of wear of the memory as a function of at least one selected point in time by preventing the memory from exceeding at least one predetermined wear level prior to at least one predetermined time.

3. The system of claim 2, wherein the at least one predetermined wear level comprises predetermined wear levels and the at least one predetermined time comprises predetermined times, with each predetermined time of the predetermined times corresponding to a different individual one of the predetermined wear levels, and wherein the performance governor circuit is adapted to control a degree of wear of the memory as a function of at least one selected point in time by preventing the memory from exceeding the predetermined wear levels prior to the respective predetermined times.

4. The system of claim 3, wherein the predetermined wear levels are wear limits of the memory at the respective predetermined times.

5. The system of claim 2, wherein the at least one predetermined time is a specified lifetime of the memory.

6. The system of claim 2, wherein the at least one predetermined wear level is a wear limit of the memory, and wherein the at least one predetermined time is a specified lifetime of the memory.

7. The system of claim 1, wherein the wear versus time profile is a predetermined constant cumulative wear rate.

8. The system of claim 7, wherein the predetermined constant cumulative wear rate is a maximum cumulative wear rate to minimally ensure that the memory meets its specified lifetime.

9. The system of claim 1, wherein the performance governor circuit is configured to maintain the wear of the memory at or below the wear versus time profile at all times during the specified lifetime of the memory.

10. The system of claim 1, wherein the performance governor circuit is configured to maintain the wear of the memory at or below the wear versus time profile for at least a portion of the specified lifetime of the memory.

11. The system of claim 1, wherein the wear versus time profile is calculated after one of a predetermined time from first use of the memory, a predetermined amount of wear of the memory or a predetermined amount of access of the memory.

12. The system of claim 1, wherein the performance governor circuit is configured to utilize alternative storage methods to prevent the wear rate of the memory from exceeding the wear versus time profile.

13. The system of claim 1 and wherein, if the performance governor circuit determines that the wear value will cause the current memory wear to exceed the wear versus time profile within the smallest possible command completion time, then the performance governor circuit effects the execution of the command to have a longer command completion time that allows a resultant current memory wear level not to exceed the wear versus time profile.

14. The system of claim 1 and wherein, if the performance governor circuit determines that the wear value will cause the current memory wear to exceed the wear versus time profile within the smallest possible command completion time, then the performance governor circuit causes the command not to be executed completely and to end with a non-completed status indication.

15. The system of claim 14 and wherein the performance governor circuit is further configured to complete an incomplete portion of the command that was not executed completely, the completion of the incomplete portion of the command is carried out upon receipt of a resubmitted command.

16. A method comprising:

receiving commands to access a memory;

controlling a degree of wear of the memory as a function of at least one selected point in time by;

preventing the wear from exceeding a wear level specified by a wear versus time profile;

determining a wear effect of executing a new command of the received commends to access the memory on a current memory wear by examining a computed wear value for the new command;

controlling execution of the new command based on the determined wear effect and based on a smallest possible command completion time of the new command; and

determining whether the computed wear value will cause the current memory wear to exceed the wear versus time profile, and if the wear value will not cause the current memory wear to exceed the wear versus time profile within the smallest possible command completion time, then executing the command.

17. The method of claim 16, wherein the wear versus time profile is a predetermined constant cumulative wear rate.

18. The method of claim 16, wherein the predetermined constant cumulative wear rate is a maximum cumulative wear rate to minimally ensure that the memory meets its specified lifetime.

19. The method of claim 16 and wherein, if the wear value will cause the current memory wear to exceed the wear versus time profile within the smallest possible command completion time, then effect the execution of the command to have a longer command completion time that allows a resultant current memory wear level not to exceed the wear versus time profile.

20. The method of claim 16 and wherein, if the wear value will cause the current memory wear to exceed the wear versus time profile within the smallest possible command completion time, then cause the command not to be executed completely and to end with a non-completed status indication.

21. The method of claim 20 and further comprising completing an incomplete portion of the command that was not executed completely, wherein the completion of the incomplete portion of the command is carried out upon receipt of a resubmitted command.