Method and circuitry for increasing reserve memory in a solid state memory disk

• US 5,586,285 A
• Filed: 02/19/1993
• Issued: 12/17/1996
• Est. Priority Date: 02/19/1993
• Status: Expired due to Fees

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Wells, Steven, Hasbun, Robert N.
• Primary Examiner(s): Robertson, David L.
• Application Number:
  US08/020,063
• Time in Patent Office: 1,397 Days
• Field of Search: 395/425, 395/497.01, 395/481, 395/427, 395/430
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/401 Compressed data
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/0664 at device level, e.g. emulation of a storage device or system
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A solid state memory disk with increased reserve memory is described. The solid state memory disk includes an array of solid state memory devices for storing user data and reserve memory, which includes both free memory and dirty memory. The solid state memory disk also includes a controller, a clean-up state machine, and a data compressor. The data compressor increases reserve memory by compressing data received from a host and coupling compressed data to the array of memory devices under the control of the controller. In response to write commands from the host, the controller writes a first sector data, which has been compressed, to a first location in a first block within a memory device. Reserve memory within the array is thus increased, so long as the maximum number of sectors the host is allowed to write is less the average compression ratio of the data compressor multiplied by the capacity of the solid state disk. A method of increasing reserve memory in a solid state disk is also described.

Claims

1. A solid state memory disk for storing a maximum number of sectors of data for a host, the solid state memory disk comprising:

a) an array of solid state memory devices which includes free memory and dirty memory, and stores sectors of valid data, the array being capable of storing the maximum number of sectors as uncompressed sectors, each memory device including a first multiplicity of blocks of memory;

b) a controller for controlling the array, the controller indicating to the host the maximum number of sectors, the controller writing a first compressed sector of valid data to a first location in a first block in the array in response to a first write command from the host, the controller writing a second compressed sector of data to a second location in a second block and marking dirty the first location in the first block in response to a second write command from the host;

c) a clean-up machine for generating free memory by erasing the first block after copying all compressed sectors of valid data within the first block out of the first block and into another block; and

d) a compressor responsive to the controller for compressing sectors of data received from the host and coupling compressed sectors of data to the array, the compressor having an average compression ratio, the compressor increasing reserve memory when the average compression ratio is greater than one, wherein the reserve memory includes free memory and dirty memory.

2. The solid state memory disk of claim 1 further comprising:

e) a decompressor responsive to the controller receiving compressed sectors of data from the array, decompressing the sector data and transferring the decompressed data to the host.

3. A solid state memory disk having reduced energy consumption, the solid state memory disk storing a maximum number of sectors of valid data for a host, the solid state memory disk comprising:

a) an array of nonvolatile memory devices for storing sectors of valid data, the array including reserve memory which includes free memory and dirty memory, the array being capable of storing a number of uncompressed sectors of valid data, each nonvolatile memory device including a first multiplicity of blocks of memory;

b) a microprocessor for controlling the array, the microprocessor indicating the maximum number of sectors to the host, the maximum number being less than an average compression ratio multiplied by the number of uncompressed sectors of valid data the array is capable of storing, the microprocessor in response to a first write command from the host writing a first compressed sector data having a first sector number to a first location in a first block in the array, the microprocessor in response to a second write command from the host writing a second compressed sector data having the first sector number to a second location in a second block and marking dirty the first compressed sector having the first sector number;

c) a clean-up machine generating free memory by erasing the first block after copying all compressed sectors of valid data within the first block out of the first block and into another block, the clean-up machine waiting a longer time to generate free memory than if the first block contained uncompressed sectors of valid data, thereby reducing energy consumption; and

d) a compressor which has the average compression ratio, the compressor being responsive to the microprocessor, the compressor compressing uncompressed sectors of valid data received from the host and passing the first compressed sector of data and the second sector of data to the array.

4. The solid state memory disk of claim 3 wherein the compressor in response to a read command from the host decompresses a compressed sector of data stored within the array and passes the decompressed data to the host.

5. The solid state memory disk of claim 3 wherein the microprocessor includes:

a) allocation means for allocating a first multiplicity of memory locations within a selected block within the array in response to a write command.

6. A method of increasing reserve memory in a solid state disk, the solid state disk including an array of nonvolatile memory devices and a compressor, the array storing sectors of valid data and including reserve memory, the reserve memory including free memory and dirty memory, the array being capable of storing a first number of uncompressed sectors, each nonvolatile memory device including a multiplicity of blocks of memory, the method including the steps of:

a) indicating to a host a maximum number of sectors of valid data that may be written to the solid state disk, the maximum number being equal to the first number of uncompressed sectors the array is capable of storing;

b) receiving a command to write a first sector of valid data from the host, the first sector of valid data being uncompressed, uncompressed sectors of valid data including a first number of bytes;

c) compressing the first sector of valid data to produce a first compressed sector of data, the first compressed sector of data including a second number of bytes, the second number of bytes being less than the first number of bytes; and

d) storing the first compressed sector of data in a first block within the array.

7. The method of claim 6 further comprising the step of:

cleaning-up a second block within the array by copying compressed sectors of valid data from the second block into a third block having sufficient reserve memory to store the compressed sectors of valid data from the second block.

8. The method of claim 7 further comprising the step of:

evaluating whether clean-up of the solid state memory disk is necessary and cleaning-up the second block only when clean-up of the solid state memory disk is necessary.

9. The method of claim 8 wherein the evaluating step comprises the steps of:

a) identifying a first number which is the amount of reserve memory within the solid state memory disk;

b) comparing a second number representative of an amount of free memory within the solid state memory disk to the first number; and

c) deciding clean-up of the solid state memory disk is necessary if the second number is less than or equal to the first number.

10. The method of claim 6 further comprising the step of:

decompressing the first compressed sector of data and transferring the first sector of valid data to the host in response to a command from the host to read the first sector of valid data.

11. A method of reducing energy consumption in a solid state disk, the solid state disk including an array of nonvolatile memory devices and a data compressor, the array storing sectors of valid data and including reserve memory, the reserve memory including free memory and dirty memory, the array having a memory capacity of a fixed number of uncompressed sectors of data, each nonvolatile memory device including a multiplicity of blocks of memory, the data compressor having an average compression ratio, the method including the steps of:

a) indicating to a host a maximum number of sectors of valid data that may be written to the solid state disk, the maximum number of sectors being less than the average compression ratio multiplied by the memory capacity;

b) receiving a command to write a first sector of valid data from the host, the first sector of valid data received from the host being uncompressed and being a first number of bytes;

c) compressing the first sector of valid data received from the host to create a first compressed sector of valid data, the first compressed sector being a second number of bytes, the second number of bytes being less than or equal to the first number of bytes;

d) storing the first compressed sector within the array; and

e) cleaning-up a selected block within the array after waiting a longer time than if the selected block uncompressed sectors of valid data, thereby reducing energy consumption the cleaning-up including the steps of;

i) selecting a first block to clean-up;

ii) allocating a sufficient amount of memory in a second block to store the first compressed sector stored within the first block;

iii) copying the first compressed sector from the first block into the second block; and

iv) erasing the first block thereby converting all memory within the first block into free memory.

12. The method of claim 11 wherein the maximum number of sectors is greater than the fixed number of uncompressed sectors, the maximum number of sectors thereby allocating to the host up to a third number of bytes whenever a compressed sector of data is stored.

13. The method of claim 11 further comprising the step of:

decompressing the first compressed sector of data to produce the first sector of valid data and coupling the first sector of valid data to the host in response to a command from the host to read the first sector of valid data.

14. The method of claim 11 wherein the cleaning-up step further comprises the step of:

evaluating whether clean-up of the solid state memory disk is necessary and cleaning-up the selected block only when clean-up of the solid state memory disk is necessary.

15. The method of claim 14 wherein the evaluating step comprises the steps of:

a) identifying a third number which is an amount of reserve memory within the solid state memory disk;

b) comparing a fourth number representative of an amount of free memory within the solid state memory disk to the first number; and

c) deciding clean-up of the solid state memory disk is necessary if the fourth number is less than the a selected percentage of the third number.

16. The method of claim 11 wherein the selecting step comprises:

a) selecting a block having a greatest amount of dirty memory.

17. The method of claim 11 wherein the allocating step comprises the steps of:

a) determining whether a compressed sector of valid data remains to be copied from the first block;

b) identifying as the second block another block with sufficient free memory to store the compressed sector of valid data; and

c) reserving sufficient memory in the second block to store the compressed sector of valid data.

18. A method of increasing reserve memory in a solid state disk, the solid state disk including an array of nonvolatile memory devices and a data compressor, the data compressor having an average compression ratio, the array storing sectors of valid data and including reserve memory, the reserve memory including free memory and dirty memory, the array having a memory capacity of a fixed number of uncompressed sectors of data, each nonvolatile memory device including a multiplicity of blocks of memory, each block of memory including a block sector translation table, each block sector translation table including a header for each sector of data stored in the block, each header including a logical sector number equal to a sector number with which the sector of valid data is associated, the method including the steps of:

a) indicating to a host a maximum number of sectors of valid data that may be written to the solid state disk, the maximum number of sectors being less than the average compression ratio multiplied by the memory capacity;

b) receiving a command to write a first sector of valid data from the host, the first sector of valid data received from the host being uncompressed and having a first sector number, the first sector of valid data from the host being a first number of bytes;

c) marking dirty a previously compressed sector of data stored within the array associated with a logical sector number equal to the first sector number;

d) compressing the first sector of valid data received from the host to create a first compressed sector of valid data, the first compressed sector being a second number of bytes that is less than the first number of bytes;

e) allocating a first amount of free memory in a first block having a first block sector translation table, the first amount of free memory being equal to the second number of bytes;

f) writing a first header for the first compressed sector into the first block sector translation table;

g) storing the first compressed sector within the first block; and

f) cleaning-up a selected block within the array, cleaning-up including the steps of;

i) selecting a second block to clean-up;

ii) on a compressed sector by compressed sector basis;

1) selecting a compressed sector from a group of compressed sectors remaining to be copied from the second block;

2) allocating sufficient free memory to store the selected compressed sector in a selected block;

3) copying the selected compressed sector from the second block into the selected block;

4) repeating steps

     1) through

     3) until all compressed sectors within the first block have been copied; and

5) erasing the second block.

19. The method of claim 18 wherein the maximum number of sector numbers is greater than the first fixed number of uncompressed sectors, the maximum number thereby allocating to the host up to a third number of bytes when a compressed sector of data is stored.

20. The method of claim 18 further comprising the step of:

decompressing the first compressed sector of data to regenerate the first sector of valid data and coupling the first sector of valid data to the host in response to a command from the host to read the first sector of valid data.

21. The method of claim 18 wherein the cleaning-up step further comprises the step of:

evaluating whether clean-up of the solid state memory disk is necessary and cleaning-up the selected block only when clean-up of the solid state memory disk is necessary.

22. The method of claim 21 wherein the evaluating step comprises the steps of:

a) identifying a third number which is an amount of reserve memory within the solid state memory disk;

b) comparing a fourth number representative of an amount of free memory within the solid state memory disk to the third number; and

c) deciding clean-up of the solid state memory disk is necessary if the fourth number is less than the a selected percentage of the third number.

23. The method of claim 18 wherein the selecting step comprises:

a) selecting a block having a greatest amount of dirty memory.

24. The method of claim 18 wherein the allocating step comprises the steps of:

a) determining whether a compressed sector of valid data remains to be copied from the first block;

b) identifying as the second block another block with sufficient free memory to store the compressed sector of valid data; and

c) reserving sufficient memory in the second block to store the compressed sector of valid data.