Nonvolatile storage device with NCQ supported and writing method for a nonvolatile storage device

• US 20090164698A1
• Filed: 06/04/2008
• Published: 06/25/2009
• Est. Priority Date: 12/24/2007
• Status: Active Grant

• Current Assignee: Skymedi Corporation
• Original Assignee: Skymedi Corporation
• Inventors: Ji, Yung-Li, Shone, Fu-Ja, Yen, Chin-Nan
• Granted Patent: US 8,583,854 B2
• Time in Patent Office: Days
• US Class Current: 711/100
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/0656 Data buffering arrangements
• CPC Class Codes: G06F 3/0676 Magnetic disk device
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G11C 16/10 Programming or data input circuits

Abstract

A nonvolatile storage device buffers multiple write commands and selects one or more therefrom according to a choosing policy to execute in priority, so as to increase the probability of continuously executing write commands corresponding to an identical smallest erasable unit, thereby reducing the frequency of backup, erasing and copyback operations and improving the efficiency of the nonvolatile storage device.

Claims

1. A writing method for a nonvolatile storage device having a plurality of smallest erasable units, comprising the steps of:

receiving a plurality of write commands;

recording the plurality of write commands and an information corresponding thereto;

choosing ones from the plurality of write commands according to the recorded information and a default choosing policy, wherein the chosen write commands are to write to a same one among the plurality of smallest erasable units; and

executing the chosen write commands in priority.

2. The writing method of claim 1, wherein the step of receiving a plurality of write commands comprises receiving the plurality of write commands by NCQ.

3. The writing method of claim 1, wherein the information includes an indication of which one or ones of the plurality of smallest erasable units are to be written by the plurality of write commands.

4. The writing method of claim 1, wherein the information includes a sequence that the plurality of write commands are received.

5. The writing method of claim 1, wherein the information includes one or more LBAs to be written thereto by the plurality of write commands.

6. The writing method of claim 1, further comprising the steps of:

receiving more write commands, which are to write to the same smallest erasable unit, during executing the chosen write commands; and

executing the more write commands in priority once the chosen write commands are executed.

7. The writing method of claim 1, further comprising selecting one from a plurality of choosing policies as the default choosing policy.

8. The writing method of claim 1, further comprising replacing the default choosing policy with a new one selected from a plurality of choosing policies.

9. The writing method of claim 8, wherein the step of replacing the default choosing policy with a new one comprises the steps of:

statistically monitoring an amount of a plurality of executed write commands; and

evaluating whether to update the default choosing policy when the amount reaches a threshold.

10. The writing method of claim 9, wherein the step of evaluating whether to update the default choosing policy when the amount reaches a threshold comprises the steps of:

statistically obtaining a counting value of operation times from the information with which the plurality of write commands will operate the plurality of smallest erasable units according to each of the choosing policies;

comparing the counting values belonging to the plurality of choosing policies for determining a best one among the plurality of choosing policies; and

setting the best choosing policy as the default choosing policy if it is still not the default choosing policy.

11. The writing method of claim 10, wherein the counting value includes erasing counts to the plurality of smallest erasable units.

12. The writing method of claim 10, wherein the counting value includes backup counts for the plurality of smallest erasable units.

13. The writing method of claim 10, wherein the counting value includes copyback counts for the plurality of smallest erasable units.

14. The writing method of claim 7, wherein the plurality of choosing policies comprise a largest fit policy, a smallest fit policy, a latest fit policy, an earliest fit policy, or a weight sort policy.

15. A nonvolatile storage device, comprising:

a plurality of smallest erasable units;

an interface for receiving a plurality of write commands to write to one or more of the plurality of smallest erasable units;

a record unit connected to the interface, for recording the plurality of write commands and an information corresponding thereto;

a choosing unit connected to the interface and the record unit, for requeuing the plurality of write commands according to the information and a default choosing policy so as to determine an executive sequence, such that the write commands corresponding to a same smallest erasable unit are continuously executed; and

a controller unit connected to the choosing unit and the plurality of smallest erasable units, for executing the write commands transferred from the choosing unit to write the plurality of smallest erasable units.

16. The nonvolatile storage device of claim 15, wherein the interface is a SATA interface with NCQ supported.

17. The nonvolatile storage device of claim 15, wherein the information includes an indication of which one or ones of the plurality of smallest erasable units are to be written by the plurality of write commands.

18. The nonvolatile storage device of claim 15, wherein the information includes a sequence that the plurality of write commands are received by the interface.

19. The nonvolatile storage device of claim 15, wherein the information includes one or more LBAs to be written thereto by the plurality of write commands.

20. The nonvolatile storage device of claim 15, wherein the controller further executes more write commands in priority after a plurality of chosen write commands are executed, which are received by the interface during the chosen write commands are executed and are to write the same smallest erasable unit written by the chosen write commands.

21. The nonvolatile storage device of claim 15, wherein the choosing unit comprises a plurality of choosing policies and selects one therefrom as the default choosing policy.

22. The nonvolatile storage device of claim 21, wherein the choosing unit comprises a learning mechanism for evaluating whether to update the default choosing policy after an amount of the write commands that have been executed reaches a threshold.

23. The nonvolatile storage device of claim 21, wherein the plurality of choosing policies comprise a largest fit policy, a smallest fit policy, a latest fit policy, an earliest fit policy, or a weight sort policy.

24. The nonvolatile storage device of claim 15, wherein the record unit comprises a memory for storing the information.

25. A writing method for a nonvolatile storage device having a plurality of data buses each connected to at least one nonvolatile memory chip, the writing method comprising the steps of:

receiving a plurality of write commands;

recording the plurality of write commands and an information corresponding thereto;

choosing and executing a first write command from the plurality of write commands; and

during a first one of the nonvolatile memory chips is busy for the first write command, choosing and executing a second write command from the plurality of write commands to write to a second one of the nonvolatile memory chips.

26. The writing method of claim 25, wherein the first and second nonvolatile memory chips are connected to a same data bus.

27. The writing method of claim 25, wherein the first and second nonvolatile memory chips are connected to two different data buses.

28. The writing method of claim 25, wherein the step of receiving a plurality of write commands comprises receiving the plurality of write commands by NCQ.