Hybrid drive garbage collecting a non-volatile semiconductor memory by migrating valid data to a disk

• US 8,341,339 B1
• Filed: 06/14/2010
• Issued: 12/25/2012
• Est. Priority Date: 06/14/2010
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Boyle, William B., Meyer, Alan T., Syu, Mei-Man L.
• Primary Examiner(s): PEUGH, BRIAN R
• Application Number:
  US12/814,662
• Time in Patent Office: 925 Days
• Field of Search: None
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/217 Hybrid disk, e.g. using both magnetic and solid state storage devices
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G06F 3/0611 in relation to response time
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/0652 Erasing, e.g. deleting, data cleaning, moving of data to a wastebasket
• CPC Class Codes: G06F 3/0685 Hybrid storage combining heterogeneous device types, e.g. hierarchical storage, hybrid arrays

Abstract

A hybrid drive is disclosed comprising a non-volatile semiconductor memory (NVSM) comprising a plurality of blocks, and a head actuated over a disk comprising a plurality of tracks, each track comprising a plurality of data sectors. A garbage collection operation is executed on the NVSM by reading valid data from a first block of the NVSM, writing the valid data to the disk, and erasing the first block.

Claims

1. A hybrid drive comprising:

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

a disk comprising a plurality of tracks, each track comprising a plurality of data sectors;

a head actuated over the disk;

control circuitry operable to execute a garbage collection operation on the NVSM by;

reading valid data from a first block of the NVSM;

writing the valid data to the disk; and

erasing the first block.

2. The hybrid drive as recited in claim 1, wherein the control circuitry is further operable to write the valid data to the disk using dynamic addressing.

3. The hybrid drive as recited in claim 2, wherein the control circuitry is further operable to execute the garbage collection operation on the NVSM by:

defining a first circular buffer on the disk comprising a plurality of the tracks; and

writing the valid data to a head of the first circular buffer.

4. The hybrid drive as recited in claim 3, wherein the control circuitry is further operable to execute the garbage collection operation by:

defining a second circular buffer on the disk comprising a plurality of the tracks;

assigning a first range of logical block addresses (LBAs) to the first circular buffer;

assigning a second range of LBAs to the second circular buffer; and

writing the valid data to one of the first and second circular buffers based on an LBA assigned to the valid data.

5. The hybrid drive as recited in claim 4, wherein the control circuitry is further operable to execute the garbage collection operation on a plurality of blocks in the NVSM in an order based on the LBAs of valid data stored in the blocks.

6. The hybrid drive as recited in claim 4, wherein the control circuitry is further operable to write host data to the first block of the NVSM based on an LBA assigned to the host data.

7. The hybrid drive as recited in claim 1, wherein the control circuitry is further operable to execute the garbage collection operation by:

determining whether to migrate the valid data to the disk; and

when the valid data should remain in the NVSM, writing the valid data to a second block of the NVSM.

8. The hybrid drive as recited in claim 7, wherein the control circuitry is further operable to determine to migrate the valid data to the disk when an age of the valid data exceeds a threshold.

9. The hybrid drive as recited in claim 7, wherein the control circuitry is further operable to determine to migrate the valid data to the disk when a write/read ratio of the valid data exceeds a threshold.

10. A method of operating a hybrid drive, the hybrid drive comprising a non-volatile semiconductor memory (NVSM) comprising a plurality of blocks, a disk comprising a plurality of tracks, each track comprising a plurality of data sectors, and a head actuated over the disk, the method comprising executing a garbage collection operation on the NVSM by:

reading valid data from a first block of the NVSM;

writing the valid data to the disk; and

erasing the first block.

11. The method as recited in claim 10, further comprising writing the valid data to the disk using dynamic addressing.

12. The method as recited in claim 11, further comprising:

defining a first circular buffer on the disk comprising a plurality of the tracks; and

writing the valid data to a head of the first circular buffer.

13. The method as recited in claim 12, further comprising:

defining a second circular buffer on the disk comprising a plurality of the tracks;

assigning a first range of logical block addresses (LBAs) to the first circular buffer;

assigning a second range of LBAs to the second circular buffer; and

writing the valid data to one of the first and second circular buffers based on an LBA assigned to the valid data.

14. The method as recited in claim 13, further comprising executing the garbage collection operation on a plurality of blocks in the NVSM in an order based on the LBAs of valid data stored in the blocks.

15. The method as recited in claim 13, further comprising writing host data to the first block of the NVSM based on an LBA assigned to the host data.

16. The method as recited in claim 10, further comprising:

determining whether to migrate the valid data to the disk; and

when the valid data should remain in the NVSM, writing the valid data to a second block of the NVSM.

17. The method as recited in claim 16, further comprising determining to migrate the valid data to the disk when an age of the valid data exceeds a threshold.

18. The method as recited in claim 16, further comprising determining to migrate the valid data to the disk when a write/read ratio of the valid data exceeds a threshold.