Techniques for obtaining a specified lifetime for a data storage device

• US 8,010,738 B1
• Filed: 06/27/2008
• Issued: 08/30/2011
• Est. Priority Date: 06/27/2008
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: More, Sachin, Chilton, Kendell A.
• Primary Examiner(s): Patel; Kaushikkumar
• Application Number:
  US12/215,432
• Time in Patent Office: 1,159 Days
• Field of Search: None
• US Class Current: 711/103
• CPC Class Codes: G11C 16/3436 Arrangements for verifying correct programming or erasure
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles

Abstract

Described are techniques for processing requests for a device. One embodiment is directed to a method including receiving a first value indicating an expected usage of said device prior to failure of said device, receiving a second value indicated a specified lifetime of said device, said second value being in units of time, determining a target rate of usage for the device in accordance with said first value and said second value, determining a current rate of usage for the device, determining whether the current rate of usage is greater than the target rate of usage; and, if said current rate of usage is greater than the target rate of usage, performing an action to reduce the current rate of usage for the device.

Claims

1. A method for processing requests for a device comprising:

receiving a first value indicating an expected usage of said device prior to failure of said device;

receiving a second value indicated a specified lifetime of said device, said second value being in units of time;

determining a target rate of usage for the device in accordance with said first value and said second value;

determining a current rate of usage for the device, wherein said determining, the current rate of usage includes adjusting a first current rate of usage using a predicted number of cumulative writes performed, said first current rate of usage being based on a number of observed write or erasures, said predicted number of cumulative writes performed being based on a number of bit failures observed in connection with writing to the device;

determining whether the current rate of usage is greater than the target rate of usage; and

if said current rate of usage is greater than the target rate of usage, performing an action to reduce the current rate of usage for the device.

2. The method of claim 1, wherein the device is a flash memory device, the first value indicates a number of writes or erasures expected with respect to the flash memory device, or a portion thereof, prior to failure of the flash memory device, and the current usage rate is determined by measuring a number of writes or erasures performed to said device, or a portion thereof, in a given time period.

3. The method of claim 2, wherein said action includes injecting one or more time delays in connection with one or more subsequent write requests.

4. The method of claim 3, wherein, upon determining that said current rate of usage is greater than the target rate of usage, the method further comprising:

holding a write request at a host for a time prior to sending the write request to a data storage system including the device for processing.

5. The method of claim 3, wherein, the device is included in a data storage system, and, upon determining that said current rate of usage is greater than the target rate of usage, the method further comprising:

modifying an amount of a resource of a data storage system allocated for use in connection with write requests for said device.

6. The method of claim 3, wherein, upon determining that said current rate of usage is greater than the target rate of usage, the method further comprising:

delaying destaging data for a write request included in a cache to said device.

7. The method of claim 3, wherein, upon determining that said current rate of usage is greater than the target rate of usage, the method further comprising:

delaying sending a response for a write request to a host that issued said write request.

8. The method of claim 1, further comprising:

revising said first value to a revised first value that is less than said first value;

determining a revised target rate of usage for the device in accordance with said revised first value and said second value; and

using said revised target rate of usage in place of said target rate of usage when performing said determining whether the current rate of usage is greater than the target rate of usage.

9. The method of claim 1, wherein said determining said current rate of usage at a first point in time for said device includes:

gathering a first set of data indicating a first characteristic of said device, said first characteristic being an indicator as to an amount of usage of said device at said first point in time;

determining, in accordance with said first set of data, a first characteristic value associated with the first characteristic; and

determining, in accordance with said first, characteristic value and a set of predicted data, a usage value providing a predicted usage of said device indicating an amount of cumulative usage of said device to said first point in time.

10. The method of claim 9, wherein said usage value is used in determining said current rate of usage for the device.

11. The method of claim 10, wherein the device is a flash memory device, the first characteristic value indicates a number of errors in connection with performing erasures or writes to said device, or portion thereof, and the set of predicted data indicates a plurality of predicted number of erasures or writes performed with respect to the device, or portion thereof, in accordance with a plurality of corresponding first characteristic values.

12. The method of claim 1, wherein the method is performed for a second device that is a disk drive, the first value indicates a number of times the device is expected to be spun up and/or spun down prior to failure, and the current usage rate indicates a number of times the device has been spun up and/or down in a given time period.

13. The method of claim 1, wherein said second value is used in determining a numeric value representing an availability of a data storage system including said device.

14. The method of claim 13, wherein said second value represents a mean time to fail for said device.

15. The method of claim 13, wherein said second value represents a mean time between failures for said device.

16. The method of claim 2, wherein said action includes at least one of:

decreasing a rate at which erasures are performed with respect to said device, or portion thereof, and decreasing a rate at which writes are performed with respect to said device, or portion thereof.

17. A data storage system comprising:

a first flash memory device wherein a number of writes or erasures W1 is expected to be performed to the first flash memory device prior to failure of said first flash memory device;

a second flash memory device wherein a number of writes or erasures W2 is expected to be performed to the second flash memory device prior to failure of said second flash memory device, W2>

W1;

a first computer readable storage medium comprising executable code stored thereon for determining target performance rates for said first flash memory device and said second flash memory device so that said first flash memory device and said second flash memory device have a same specified lifetime, said first computer readable storage medium comprising executable code stored thereon for;

determining a first target performance rate for said first flash memory device n accordance with W1 and a value indicating a specified lifetime in units of time; and

determining a second target performance rate for said second flash memory device in accordance with W2 and said value indicating a specified lifetime in units of time; and

a second computer readable storage medium comprising executable code stored thereon for;

determining a current performance rate for one of said first flash memory device and said second flash memory device, wherein said, determining the current performance rate includes adjusting a first current rate of usage for said one flash memory device using a predicted number of cumulative writes performed, the first current rate of usage being based on a number of observed write or erasures, the predicted number of cumulative writes performed being based on a number of bit failures observed in connection with writing to said one flash memory device;

determining whether said current performance rate for said one flash memory device is greater than a corresponding one of the first and the second target performance rates for said one flash memory device; and

if said current performance rate is greater than the corresponding target performance rate, performing an action to reduce the current performance rate.

18. The data storage system of claim 17, wherein said action includes at least one of decreasing a rate at which erasures are performed with respect to said one flash memory device, or portion thereof, and decreasing a rate at which writes are performed with respect to said one flash memory device, or portion thereof.

19. A method for obtaining a desired lifetime of an entity comprising:

receiving a first value indicating an expected usage of said entity prior to failure of said entity;

receiving a second value indicated a specified lifetime of said entity, said second value being in units of time;

determining a target rate of usage for the entity in accordance with said first value and said second value;

determining a current rate of usage for the entity, wherein said determining the current rate of usage includes adjusting a first current rate of usage using a predicted number of cumulative writes performed, said first current rate of usage being based on a number of observed write or erasures, said predicted number of cumulative writes performed being based on a number of bit failures observed in connection with writing to the entity;

determining whether the current rate of usage is greater than the target rate of usage; and

if said current rate of usage is greater than the target rate of usage, performing an action to reduce the current rate of usage for the entity.

20. The method of claim 19, wherein the entity is a first entity and the steps of said method are performed for said first entity and the method steps are performed for a second entity so that said first entity and said second entity have said specified lifetime.