Storage device and operating method thereof

1. A storage device comprising:

a nonvolatile memory;

a controller configured to control a write operation of the nonvolatile memory according to a write request received from a host and transmit a response to the write request to the host; and

write buffers configured to store write data received with the write request,

wherein the controller is further configured to:

set a response transmission delay time based on an available size of the write buffers, a minimum response transmission delay time, and a maximum response transmission delay time,

transmit the response to the write request to the host after the response transmission delay time passes, and

dynamically adjust, as the available size of the write buffers changes, the response transmission delay time within a range from the minimum response transmission delay time to the maximum response transmission delay time,

wherein the controller determines the minimum response transmission delay time based on the maximum response transmission delay time and an average response transmission delay time.

2. The storage device according to claim 1 ,

wherein the controller includes a command queue that stores the write request, and

wherein the controller determines the maximum response transmission delay time by using a depth of the command queue and a target response transmission delay time corresponding to the depth of the command queue.

3. The storage device according to claim 1 , wherein the controller determines the average response transmission delay time based on a total size of the write buffers, a threshold usage size of the write buffers at which response transmission delay to the host is triggered, and a maximum pending time for the write operation.

4. The storage device according to claim 3 , wherein the controller sets, as the minimum response transmission delay time, a time at which actual usage size of the write buffers reaches the threshold usage size of the write buffers.

5. The storage device according to claim 1 , wherein the controller sets the response transmission delay time based further on the total size of the write buffers and the threshold usage size of the write buffers, at which response transmission delay to the host is triggered.

6. The storage device according to claim 1 , wherein the controller sets the response transmission delay time in a direction approaching the maximum response transmission delay time as the available size of the write buffers decreases.

7. The storage device according to claim 1 , wherein the controller sets the response transmission delay time in a direction approaching the minimum response transmission delay time as the available size of the write buffers increases.

8. The storage device according to claim 1 , wherein the controller comprises:

a host interface configured to interface with the host;

a processor configured to control overall operations of the controller;

a memory interface configured to interface with the nonvolatile memory; and

a response delay configured to monitor the write buffers in real-time and dynamically set the response transmission delay time according to a change in the available size of the write buffers.

9. The storage device according to claim 8 , wherein the response delay comprises:

a write buffer monitor configured to acquire the available size from the write buffer;

a response transmission delay time calculator configured to set the response transmission delay time by using the available size of the write buffers acquired by the write buffer monitor; and

a response generator configured to generate a response and transmit the response to the host interface after the set response transmission delay time passes.

10. An operating method of a storage device including a nonvolatile memory, a controller, and write buffers, the operating method comprising:

receiving, by the controller, a write request and write data from a host;

acquiring, by the controller from the write buffers, buffer usage information including an available size of the write buffers;

setting, by the controller, a response transmission delay time based on the available size of the write buffers, a minimum response transmission delay time, and a maximum response transmission delay time;

transmitting, by the controller, a response to the write request to the host after the set response transmission delay time passes; and

dynamically adjusting, by the controller, as the available size of the write buffers changes, the response transmission delay time within a range from the minimum response transmission delay time to the maximum response transmission delay time,

wherein the minimum response transmission delay time is determined based on the maximum response transmission delay time and an average response transmission delay time.

11. The operating method according to claim 10 , further comprising:

determining, by the controller, whether an actual usage size of the write buffers is greater than or equal to a threshold usage size of the write buffers, at which response transmission delay to the host is triggered.

12. The operating method according to claim 11 , wherein, when the actual usage size of the write buffers is greater than or equal to the threshold usage size of the write buffers, the controller sets the response transmission delay time.

13. The operating method according to claim 11 , wherein, when the actual usage size of the write buffers is less than the threshold usage size of the write buffers, the controller transmits to the host the response to the write request without delay after the write data is stored in the write buffer.

14. The operating method according to claim 10 , further comprising:

determining, by the controller, the maximum response transmission delay time based on a depth of a command queue in the storage device and storing the write request and a target response transmission delay time corresponding to the depth of the command queue.

15. The operating method according to claim 14 , further comprising:

determining, by the controller, the average response transmission delay time based on a total size of the write buffers, the threshold usage size of the write buffers at which response transmission delay to the host is triggered, and a maximum pending time for a write operation of storing the write data in the nonvolatile memory.

16. The operating method according to claim 10 , wherein the setting of the response transmission delay time is also based on the total size of the write buffers and the threshold usage size of the write buffers, in which response transmission delay to the host is triggered.

17. A controller for controlling a memory device, the controller comprising:

a write buffer configured to buffer write data to be stored in the memory device;

a command queue configured to queue a write request corresponding to the write data;

a response delay configured to respond to the write request according to an actual response transmission delay time based on a total size of the write buffer, a threshold usage size of the write buffer, a currently available size of the write buffer, and minimum and maximum response transmission delay times; and

a processor configured to control the memory device to store therein the write data in response to the write request,

wherein the minimum response transmission delay time is determined based on the maximum response transmission delay time and an average response transmission delay time.

18. The controller of claim 17 , wherein the maximum response transmission delay time is based on depth of the command queue.