Granted Patent B1

US 9,442,668 · App. 14/090,117 · Granted Sep 13, 2016

Abstract

Claims (38)

1. A data storage device (DSD) comprising:

a storage medium configured to operate in a first power state and a second power state;

a memory configured to store a service queue of service requests to access the storage medium; and

a controller configured to:

perform one or more of the service requests in the service queue;

determine a command rate of service requests received by the DSD;

determine an average latency in performing the one or more service requests;

calculate an estimated command rate based at least on the determined command rate and using the average latency as feedback to control a rate of decay of the estimated command rate;

determine a timer interpolation value based at least on the estimated command rate and a probability of the DSD receiving no service requests within a time interval; and

determine when to transition between the first power state and the second power state based on the timer interpolation value.

2. The DSD of claim 1 , wherein the first power state comprises a high power state and the second power state comprises a low power state.

3. The DSD of claim 1 , wherein the controller is further configured to use a counter to determine the command rate.

4. The DSD of claim 1 , wherein the controller is further configured to set, based on the timer interpolation value, timer values for an amount of time to wait without receiving a service request before transitioning between power states of the storage medium.

5. The DSD of claim 1 , wherein the storage medium comprises a hard disk.

6. The DSD of claim 1 , wherein the storage medium comprises a solid state memory.

7. The DSD of claim 1 , wherein the controller is further configured to determine the probability that no service requests will arrive within the time interval based on a Poisson distribution.

8. The DSD of claim 1 , wherein the time interval corresponds to a break even time needed to transition between the first power state and the second power state.

9. The DSD of claim 1 , wherein the controller is further configured to determine a threshold based on a desired probability of receiving no service requests within the time interval and to transition from the first power state to the second power state when the threshold is met.

10. A method for managing energy consumption in a data storage device (DSD), the method comprising:

determining a command rate of service requests received by the DSD;

determining an average latency in performing the one or more service requests;

calculating an estimated command rate based at least on the determined command rate and using the average latency as feedback to control a rate of decay of the estimated command rate;

determining a timer interpolation value based at least on the estimated command rate and a probability of receiving no service requests within a time interval; and

determining when to transition between power states of the DSD based on the timer interpolation value to.

11. The method of claim 10 , further comprising:

setting, based on the timer interpolation value, timer values for an amount of time to wait without receiving a service request before transitioning between power states of the storage medium; and

switching between the power states based on the timer values.

12. The method of claim 10 , wherein determining the probability of receiving no service requests further comprises using a Poisson distribution.

13. The method of claim 10 , wherein the time interval corresponds to a break even time needed to transition between a first power state and a second power state.

14. The method of claim 10 , further comprising:

determining a threshold based on a desired probability of receiving no service requests within the time interval; and

transitioning the DSD from a first power state to a second power state when the threshold is met.

15. A non-transitory computer-readable medium storing computer executable instructions for managing energy consumption in a data storage device (DSD), wherein when the computer executable instructions are executed by a controller, the computer executable instructions cause the controller to:

determine a command rate of service requests received by the DSD;

determine an average latency in performing the one or more service requests;

calculate an estimated command rate based at least on the determined command rate and using the average latency as feedback to control a rate of decay of the estimated command rate;

determine a timer interpolation value based at least on the estimated command rate and a probability of the DSD receiving no service requests within a time interval; and

determine when to transition between the first power state and the second power state based on the timer interpolation value.

Assignments (8)