STORAGE DEVICE THAT COMPRESSES DATA RECEIVED FROM A HOST BEFORE WRITING THEREIN

• US 20180088811A1
• Filed: 03/01/2017
• Published: 03/29/2018
• Est. Priority Date: 09/23/2016
• Status: Active Grant

• Current Assignee: Kioxia Corporation
• Original Assignee: Toshiba Memory Corporation (Kioxia Corporation)
• Inventors: KANNO, Shinichi
• Granted Patent: US 10,635,310 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/1044 Space efficiency improvement
• CPC Class Codes: G06F 2212/214 Solid state disk
• CPC Class Codes: G06F 2212/401 Compressed data
• CPC Class Codes: G06F 2212/7201 Logical to physical mapping or translation of blocks or pages
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G06F 3/0604 Improving or facilitating administration, e.g. storage management
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/0638 Organizing or formatting or addressing of data
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]

Abstract

A storage device includes a nonvolatile storage and a controller. The controller is configured to compress data received from a host in association with a write command designating a first data length as a length of the data and a starting logical address of the data, into compressed data of a second data length shorter than the first data length, write the compressed data in the nonvolatile storage. Further, the controller is configured to generate an address mapping for the data, such that a first logical address range that starts at the starting logical address is mapped to a physical region of the nonvolatile storage having a size equal to the second data length, and a second logical address range that directly follows the first logical address range is not mapped to any physical region of the nonvolatile storage.

Claims

1. A storage device comprising:

a nonvolatile storage; and

a controller configured to

compress data received from a host in association with a write command designating a first data length as a length of the data and a starting logical address of the data, into compressed data of a second data length shorter than the first data length,

write the compressed data in the nonvolatile storage, and

generate an address mapping for the data, such that a first logical address range that starts at the starting logical address and is mapped to a physical region of the nonvolatile storage having a size equal to the second data length, and a second logical address range that directly follows the first logical address range is not mapped to any physical region of the nonvolatile storage.

2. The storage device according to claim 1, wherein the second logical address range includes a number of data blocks having a total size that is equal to a size difference between the first and second data lengths.

3. The storage device according to claim 2, wherein

the controller is further configured to return a response indicating an error, responsive to a read or write command that designates a logical address that is within the first address range that is different from the starting logical address or is within the second address range.

4. The storage device according to claim 1, wherein

the controller is further configured to read the compressed data from the physical region of the nonvolatile storage, the physical region being determined by referring to the address mapping, responsive to a read command that designates the starting logical address and the first data length.

5. The storage device according to claim 1, wherein

the controller compresses the data received from the host according to a compression method designated by the write command.

6. The storage device according to claim 1, wherein

the controller is further configured to write the data received from the host without compressing the data, when the write command does not designate any data compression.

7. The storage device according to claim 1, wherein

the controller is further configured to independently maintain an address mapping for each of a plurality of namespaces that is established in the storage device, and compress the data received from the host according to a compression method associated with a namespace designated by the write command.

8. The storage device according to claim 1, wherein

the controller is further configured to select a plurality of blocks of the nonvolatile storage as target blocks for garbage collection, determine whether or not valid data stored in the selected blocks are compressed, expand and re-compress the valid data when the valid data are determined to be compressed, and copy the re-compressed valid data and other valid data from the selected blocks to another block.

9. The storage device according to claim 1, wherein

the controller is further configured to select a plurality of blocks of the nonvolatile storage as target blocks for garbage collection, determine whether or not valid data stored in the selected blocks are compressed, expand and re-compress the valid data when the valid data are determined to be compressed and an update frequency of the valid data is lower than a threshold, and copy the re-compressed valid data and other valid data from the selected blocks to another block.

10. The storage device according to claim 1, wherein

the controller is further configured to count a number of times data stored in each block of the nonvolatile storage have been copied through garbage collection, select a plurality of blocks for which counted numbers are equal as target blocks for garbage collection, determine whether or not valid data stored in the selected blocks are compressed, expand and re-compress the compressed valid data upon determining that the counted number for the target blocks is greater than a threshold, and copy the re-compressed valid data and other valid data from the selected blocks to another block.

11. A method for operating a storage device including a nonvolatile storage, comprising:

compressing data received from a host in association with a write command designating a first data length as a length of the data and a starting logical address of the data, into compressed data of a second data length shorter than the first data length;

writing the compressed data in the nonvolatile storage; and

generating an address mapping for the data, such that a first logical address range that starts at the starting logical address and is mapped to a physical region of the nonvolatile storage having a size equal to the second data length, and a second logical address range that directly follows the first logical address range is not mapped to any physical region of the nonvolatile storage.

12. The storage device according to claim 11, wherein the second logical address range includes a number of data blocks having a total size that is equal to a size difference between the first and second data lengths.

13. The method according to claim 11, further comprising:

returning a response indicating an error, responsive to a read or write command that designates a logical address that is within the first address range that is different from the starting logical addressor is within the second address range.

14. The method according to claim 11, further comprising:

reading the compressed data from the physical region of the nonvolatile storage, the physical region being determined by referring to the address mapping, responsive to a read command that designates the starting logical address and the first data length.

15. The method according to claim 11, wherein

the data received from the host are compressed according to a compression method designated by the write command.

16. The method according to claim 11, further comprising:

writing the data received from the host without compressing the data, when the write command does not designate any data compression.

17. The method according to claim 11, further comprising:

independently maintaining an address mapping for each of a plurality of namespaces that is established in the storage device, wherein

the data received from the host are compressed according to a compression method associated with a namespace designated by the write command.

18. The method according to claim 11, further comprising:

selecting a plurality of blocks of the nonvolatile storage as target blocks for garbage collection;

determining whether or not valid data stored in the selected blocks are compressed;

expanding and re-compressing the valid data when the valid data are determined to be compressed; and

copying the re-compressed valid data and other valid data from the selected blocks to another block.

19. The method according to claim 11, further comprising:

selecting a plurality of blocks of the nonvolatile storage as target blocks for garbage collection;

determining whether or not valid data stored in the selected blocks are compressed;

expanding and re-compressing the valid data when the valid data are determined to be compressed and an update frequency of the valid data is lower than a threshold; and

copying the re-compressed valid data and other valid data from the selected blocks to another block.

20. The method according to claim 11, further comprising:

counting a number of times data stored in each block of the nonvolatile storage have been copied through garbage collection; and

selecting a plurality of blocks for which counted numbers are equal as target blocks for garbage collection;

determining whether or not valid data stored in the selected blocks are compressed;

expanding and re-compressing the compressed valid data upon determining that the counted number for the target blocks is greater than a threshold; and

copying the re-compressed valid data and other valid data from the selected blocks to another block.