Hybrid drive copying disk cache to non-volatile semiconductor memory

• US 8,782,334 B1
• Filed: 08/10/2011
• Issued: 07/15/2014
• Est. Priority Date: 09/10/2010
• Status: Active Grant

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Boyle, William B., Stevens, Curtis E., Coker, Kenny T.
• Primary Examiner(s): Bradley, Matthew
• Assistant Examiner(s): GOLDSCHMIDT, CRAIG S
• Application Number:
  US13/207,184
• Time in Patent Office: 1,070 Days
• Field of Search: 711/111, 369/43, 369 4411- 4441, 360 69- 7815
• US Class Current: 711/111
• CPC Class Codes: G06F 12/0868 Data transfer between cache memory and other subsystems, e.g. storage devices or host systems
• CPC Class Codes: G06F 2212/214 Solid state disk
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/0605 by facilitating the interaction with a user or administrator
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0625 Power saving in storage systems
• CPC Class Codes: G06F 3/0656 Data buffering arrangements
• CPC Class Codes: G06F 3/068 Hybrid storage device
• CPC Class Codes: G06F 3/0686 Libraries, e.g. tape libraries, jukebox
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A hybrid drive is disclosed comprising a head actuated over a disk comprising a plurality of data sectors. The hybrid drive further comprises a non-volatile semiconductor memory (NVSM) comprising a plurality of memory segments. A disk cache is defined comprising a first plurality of the data sectors, and a non-cache area of the disk is defined comprising a second plurality of the data sectors. When a write command is received from a host, data is written to the disk cache, and under certain conditions, the data is copied from the disk cache to the NVSM.

Claims

1. A hybrid drive comprising:

a disk comprising a plurality of data sectors;

a head actuated over the disk;

a non-volatile semiconductor memory (NVSM) comprising a plurality of memory segments;

control circuitry operable to;

define a disk cache comprising a first plurality of the data sectors;

define a non-cache area of the disk comprising a second plurality of the data sectors;

receive a write command from a host, the write command comprising data;

write the data to the disk cache; and

copy the data from the disk cache to the NVSM.

2. The hybrid drive as recited in claim 1, wherein the control circuitry is further operable to flush the data in the disk cache to the non-cache area of the disk.

3. The hybrid drive as recited in claim 1, wherein the control circuitry is further operable to copy the data from the disk cache to the NVSM when entering a power save mode.

4. The hybrid drive as recited in claim 1, wherein the control circuitry is further operable to:

load the head from a ramp to position the head over the disk;

unload the head from the disk onto the ramp; and

when a number of load/unload operations exceeds a threshold, copy the data from the disk cache to the NVSM and disable servoing of the head without unloading the head onto the ramp.

5. The hybrid drive as recited in claim 1, wherein the control circuitry is further operable to:

load the head from a ramp to position the head over the disk;

unload the head from the disk onto the ramp; and

when vibrations are detected and a number of load/unload operations exceeds a threshold, copy the data from the disk cache to the NVSM, unload the head onto the ramp, and spin down the disk.

6. The hybrid drive as recited in claim 1, wherein the control circuitry is further operable to:

maintain a number of consecutive read commands received from the host, wherein each of the consecutive read commands is serviced by reading from one of the NVSM and the disk cache; and

copy the data from the disk cache to the NVSM and spin down the disk when the number of consecutive read commands exceeds a threshold.

7. The hybrid drive as recited in claim 6, wherein while the disk is spun down the control circuitry is further operable to:

receive a read command from the host to read from the non-cache area of the disk;

spin up the disk and read from the non-cache area of the disk; and

determine whether to spin down the disk after reading from the non-cache area of the disk.

8. The hybrid drive as recited in claim 1, wherein the control circuitry is further operable to:

write the disk cache as a circular buffer comprising a buffer head;

spin up the disk and save the buffer head location;

service write commands from the host by writing to the disk cache; and

prior to spinning down the disk, copy part of the disk cache to the NVSM corresponding to a current buffer head location and the saved buffer head location.

9. The hybrid drive as recited in claim 1, wherein the control circuitry is further operable to:

spin up the disk; and

copy valid data from memory segments of the NVSM to the disk cache.

10. The hybrid drive as recited in claim 9, wherein after copying the valid data to the disk cache, the control circuitry is further operable to erase the memory segments of the NVSM comprising the valid data.

11. The hybrid drive as recited in claim 1, wherein the control circuitry is further operable to:

define a NVSM cache comprising a plurality of the memory segments; and

determine, based on a usage ratio between the NVSM cache and the disk cache, whether to write the data to one of the NVSM cache and the disk cache.

12. A hybrid drive comprising:

a disk comprising a plurality of data sectors;

a head actuated over the disk;

a non-volatile semiconductor memory (NVSM) comprising a plurality of memory segments;

control circuitry operable to;

define a disk cache comprising a first plurality of the data sectors;

define a non-cache area of the disk comprising a second plurality of the data sectors;

define a NVSM cache comprising a plurality of the memory segments;

receive a write command from a host, the write command comprising data;

determine whether to write the data to one of the NVSM cache and the disk cache;

write the data to the disk cache; and

copy the data from the disk cache to the NVSM.

13. The hybrid drive as recited in claim 12, wherein the control circuitry is further operable to determine to write the data to the disk cache when the data is assigned to logical block addresses written to more frequently than logical block addresses written to an average number of times.

14. A method of operating a hybrid drive comprising a head actuated over a disk comprising a plurality of data sectors, and a non-volatile semiconductor memory (NVSM) comprising a plurality of memory segments, the method comprising:

defining a disk cache comprising a first plurality of the data sectors;

defining a non-cache area of the disk comprising a second plurality of the data sectors;

receiving a write command from a host, the write command comprising data;

writing the data to the disk cache; and

copying the data from the disk cache to the NVSM.

15. The method as recited in claim 14, further comprising flushing the data in the disk cache to the non-cache area of the disk.

16. The method as recited in claim 14, further comprising copying the data from the disk cache to the NVSM when entering a power save mode.

17. The method as recited in claim 14, further comprising:

loading the head from a ramp to position the head over the disk;

unloading the head from the disk onto the ramp; and

when a number of load/unload operations exceeds a threshold, copying the data from the disk cache to the NVSM and disabling servoing of the head without unloading the head onto the ramp.

18. The method as recited in claim 14, further comprising:

loading the head from a ramp to position the head over the disk;

unloading the head from the disk onto the ramp; and

when vibrations are detected and a number of load/unload operations exceeds a threshold, copying the data from the disk cache to the NVSM, unloading the head onto the ramp, and spinning down the disk.

19. The method as recited in claim 14, further comprising:

maintaining a number of consecutive read commands received from the host, wherein each of the consecutive read commands is serviced by reading from one of the NVSM and the disk cache; and

copying the data from the disk cache to the NVSM and spinning down the disk when the number of consecutive read commands exceeds a threshold.

20. The method as recited in claim 19, wherein while the disk is spun down further comprising:

receiving a read command from the host to read from the non-cache area of the disk;

spinning up the disk and reading from the non-cache area of the disk; and

determining whether to spin down the disk after reading from the non-cache area of the disk.

21. The method as recited in claim 14, further comprising:

writing the disk cache as a circular buffer comprising a buffer head;

spinning up the disk and saving the buffer head location;

servicing write commands from the host by writing to the disk cache; and

prior to spinning down the disk, copying part of the disk cache to the NVSM corresponding to a current buffer head location and the saved buffer head location.

22. The method as recited in claim 14, further comprising:

spinning up the disk; and

copying valid data from memory segments of the NVSM to the disk cache.

23. The method as recited in claim 22, wherein after copying the valid data to the disk cache, further comprising erasing the memory segments of the NVSM comprising the valid data.

24. The method as recited in claim 14, further comprising:

defining a NVSM cache comprising a plurality of the memory segments; and

determining, based on a usage ratio between the NVSM cache and the disk cache, whether to write the data to one of the NVSM cache and the disk cache.

25. A method of operating a hybrid drive comprising a head actuated over a disk comprising a plurality of data sectors, and a non-volatile semiconductor memory (NVSM) comprising a plurality of memory segments, the method comprising:

defining a disk cache comprising a first plurality of the data sectors;

defining a non-cache area of the disk comprising a second plurality of the data sectors;

defining a NVSM cache comprising a plurality of the memory segments;

receiving a write command from a host, the write command comprising data;

determining whether to write the data to one of the NVSM cache and the disk cache;

writing the data to the disk cache; and

copying the data from the disk cache to the NVSM.

26. The method as recited in claim 25, further comprising determining to write the data to the disk cache when the data is assigned to logical block addresses written to more frequently than logical block addresses written to an average number of times.