Storage device that stores setting values for operation thereof

1. A storage device, comprising:

a volatile memory;

a nonvolatile memory;

an auxiliary power source; and

a controller configured to start a setting process to store a setting value into the volatile memory in response to a setting command received from a host, and to operate in accordance with one or more setting values stored in the volatile memory, said one or more setting values including a setting value corresponding to frequency of processing to be performed with respect to the nonvolatile memory, wherein

when the controller determines that a main power supply will stop, power supply from the auxiliary power source starts to be primarily used, and the controller saves at least part of said one or more setting values stored in the volatile memory into the nonvolatile memory, before the power supply from the auxiliary power source ends.

2. The storage device according to claim 1 , further comprising:

a voltage detection circuit configured to detect a voltage value of the main power supply and output the detected voltage value to the controller, wherein

when the detected voltage value is smaller than a threshold, the controller determines that the main power supply will stop.

3. The storage device according to claim 1 , wherein

in response to a power off notification from the host, the controller saves said one or more setting values in the volatile memory into the nonvolatile memory using power supply of the main power supply, and then shuts off the main power supply.

4. The storage device according to claim 1 , wherein

when the controller determines that the main power supply will stop, the controller also saves data stored in the volatile memory, which is different from said one or more setting values therein, before saving said one or more setting values.

5. The storage device according to claim 4 , wherein

the data different from said one or more setting values include user data instructed to be stored in the nonvolatile memory by the host.

6. The storage device according to claim 5 , wherein

the data different from said one or more setting values include also a transaction log, and the transaction log is saved into the nonvolatile memory before the user data.

7. The storage device according to claim 4 , wherein

in response to determining that the setting process is being carried out when the controller determines that the main power supply will stop, the controller carries out saving of the data different from said one or more setting values, after interrupting the setting process.

8. The storage device according to claim 7 , wherein

after the saving of the data different from said one or more setting values, the controller resumes the setting process, and then carries out saving of the setting values stored in the volatile memory through the setting process to the nonvolatile memory.

9. The storage device according to claim 7 , wherein

after the saving of the data different from said one or more setting values, the controller determines whether or not saving of the setting value to be stored in the volatile memory through the setting process to the nonvolatile memory can be completed before the power supply from the auxiliary power source ends,

when it is determined that the saving can be completed, the controller resumes the setting process, and then carries out the saving of the setting value into the nonvolatile memory, and

when it is determined that the saving cannot be completed, the controller carries out saving of a corresponding current setting value into the nonvolatile memory without resuming the setting process.

10. The storage device according to claim 1 , wherein

the volatile memory includes a first memory region and a second memory region,

during the setting process, the controller stores the setting value into the first memory region and then copies the setting value in the first memory region to the second memory region, and

when the controller determines that the main power supply will stop, the controller saves at least part of one or more setting values in the second memory region of the volatile memory into a third memory region of the nonvolatile memory.

11. The storage device according to claim 10 , wherein

when a setting value in the second memory region is the same as a corresponding setting value in the third memory region, the controller does not save the setting value in the second memory region into the third memory region.

12. The storage device according to claim 10 , wherein

the first memory region is included in the second memory region.

13. The storage device according to claim 10 , wherein

during the setting process, the controller stores, into the second memory region, management information indicating whether or not the setting value has been copied to the second memory region, and

when the controller determines that the main power supply will stop, the controller saves the management information corresponding at least part of one or more setting values in the second memory region into the third memory region of the nonvolatile memory.

14. The storage device according to claim 13 , wherein

when the storage device starts operating, the controller reads management information corresponding to a setting value from the third memory region,

when the read management information indicates that the setting value has been copied to the second memory region, the controller copies the setting value in the third memory region to the first and second memory regions, and

when the read management information indicates that the setting value has not been copied to the second memory region, the controller writes a default setting value in the first and second memory regions.

15. The storage device according to claim 10 , wherein

the controller is configured to adjust a size of the second memory region based on remaining capacity of the auxiliary power source.

16. A storage device, comprising:

a volatile memory;

a nonvolatile memory; and

a controller configured to start a setting process to store a setting value into the volatile memory in response to a setting command received from a host, and to operate in accordance with the setting value stored in the volatile memory, the setting value including a setting value corresponding to frequency of processing to be performed with respect to the nonvolatile memory, wherein

when the storage device is turned off without the setting value being stored in the volatile memory through the setting process, upon restart of the storage device, the controller reads a default value from the nonvolatile memory and writes the read default value into the volatile memory.

17. A storage device, comprising:

a volatile memory;

a nonvolatile memory; and

a controller configured to start one or more setting processes to store one or more setting values into the volatile memory in response to one or more setting commands received from a host, and to operate in accordance with said one or more setting values stored in the volatile memory, wherein

when power supply to the storage device from a power source will stop, the controller saves a part of said one or more setting values in the volatile memory into the nonvolatile memory, and does not save another part of said one or more setting values in the volatile memory into the nonvolatile memory, before the power supply to the controller ends.

18. The storage device according to claim 17 , wherein

said one or more setting values stored in the volatile memory includes a setting value corresponding to frequency of a processing to be performed with respect to the nonvolatile memory.