SOLID STATE STORAGE SYSTEM THAT EVENLY ALLOCATES DATA WRITING/ERASING OPERATIONS AMONG BLOCKS AND METHOD OF CONTROLLING THE SAME

• US 20100023677A1
• Filed: 03/02/2009
• Published: 01/28/2010
• Est. Priority Date: 07/28/2008
• Status: Abandoned Application

• Current Assignee: PaxDisk Co., Ltd., Hynix Semiconductor Incorporated (SK Hynix Inc.)
• Original Assignee: PaxDisk Co., Ltd.
• Inventors: SHIN, Young Kyun, YI, Dae Hee
• Application Number:
  US12/395,755
• Publication Number:
  US 20100023677A1
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7211 Wear leveling

Abstract

A solid state storage system that evenly allocates data writing/erasing operations among blocks is presented. The solid state storage system includes a controller. The controller is configured to set a representative value that becomes a block allocation reference in accordance with predetermined information of blocks in a flash memory area. The controller is also configured to calculate a data value that becomes life time information according to the predetermined information in a current state for each block. The controller is also configured to determine a block where a deviation is generated between the representative value and the data value. The controller is also configured to allocate block where the deviation is generated as a new block where data is written.

Claims

1. A solid state storage system, comprising:

a controller configured to;

set a representative value that becomes a block allocation reference in accordance to predetermined information of blocks in a flash memory area,

calculate a data value that becomes life time information in accordance to the predetermined information in a current state for each block,

determine a block where a deviation is generated between the representative value and the data value, and

allocate data to be written to the determined block where the deviation is generated.

2. The solid state storage system of claim 1, wherein the controller further configured to:

set the representative value as a logical threshold value of a reference block as a function of the predetermined information comprising a size of each block in the memory area, a number of pages in each block, and a write count in each block; and

control block allocation from blocks within a same plane as a function of which block within the same plane is associated with a largest deviation between the data value and the representative value.

3. The solid state storage system of claim 2,

wherein the controller is configured to provide the data value by using a size of each block in the flash memory area, the number of pages in each block, and a current write count in each corresponding block as the predetermined information for each corresponding block.

4. The solid state storage system of claim 2,

wherein when the deviation between the data value of each block and the representative value is less than a predetermined value, then the controller is enabled to initialize information to each block.

5. A solid state storage system, comprising:

a flash memory area configured to include a plurality of planes, each plane having a free block and a data block;

a controller configured to;

set a representative value in accordance to a statistical value of predetermined information of the each block,

calculate a data value which is indicative of limited life time information of each block such that the data value is calculated in accordance to the predetermined information in a current state for each block, and

determine priority of block allocation for each block using a deviation between the representative value and the data value of each block; and

a buffer unit configured to update and store the data value for each block when a write operation is performed on each block.

6. The solid state storage system of claim 5,

wherein the controller is configured to determine blocks where the deviation is generated between the representative value and the data value is less than the predetermined value, and configured to preferentially allocate blocks, having deviations furthest from the predetermined value, as new blocks where data is to be written.

7. The solid state storage system of claim 5, wherein the controller includes:

a representative value setting unit configured to set the representative value, corresponding to a logical threshold value of each block, by using the predetermined information comprising the size of each free block, the size of each data block, the number of pages in each block, and a write count in each block; and

a block control unit configured to perform a control operation such that block allocation is made on blocks in the same plane where the deviation between the data value and the representative value is largest.

8. The solid state storage system of claim 7,

wherein the representative value setting unit is configured to provide the data value of each block by using a size of each block in the flash memory area, by using the number of pages in each block, and by using a current write count in each block as the predetermined information for each block.

9. The solid state storage system of claim 7,

wherein the block control unit is configured to initialize information of each block when the deviation between the data value of each block and the representative value is less than or equal to a predetermined value.

10. The solid state storage system of claim 5, wherein the buffer unit includes:

an intra-block data value storage unit configured to store the data value which is updated for each block when a write operation is performed; and

a write count storage unit configured to store a write count for each plane, if the intra-block data value storage unit is initialized when the deviation between the data value and the representative value is less than or equal to the predetermined value.

11. The solid state storage system of claim 10,

wherein, when the write count for each plane is stored whenever the intra-block data value storage unit is initialized, such that the write count is stored by being increased by a logical threshold value indicated by the representative value.

12. The solid state storage system of claim 5,

wherein the controller is configured to include an address mapping control unit, and

the address mapping control unit is configured to perform a control operation such that continuous logical addresses are mapped to physical addresses of blocks in different planes.

13. The solid state storage system of claim 12,

wherein the logical addresses in the same plane are increased by the number of planes.

14. The solid state storage system of claim 12,

wherein the address mapping control unit is configured to control address mapping using a flash translation layer (FTL) conversion.

15. A method of controlling a solid state storage system, comprising:

allowing a controller to set a representative value that becomes a block allocation reference in accordance to predetermined information of blocks and allowing the controller to calculate a data value that becomes life time information according to the predetermined information of each block in a current state for each block;

determining whether there are any blocks in which a deviation between the representative value and the data value is less than or equal to a predetermined value, when data is processed in accordance to a command from an external host;

performing a write operation when corresponding blocks exist that have deviations between the representative value and the data value less than or equal to a predetermined value; and

allowing the controller to initialize information of all of the blocks when the corresponding blocks do not have deviations between the representative value and the data value less than or equal to a predetermined value.

16. The method of claim 15,

wherein the representative value corresponds to a maximum write count of each block is set using a size of each block in the memory area, using a number of pages in each block, and using a write count in each block as the predetermined information.

17. The method of claim 15,

wherein, in the step of determining of whether the corresponding blocks exist, a control operation is performed to determine deviations between the data value and the representative value and the control operation preferentially allocates data to the corresponding blocks that have large deviations which are less than or equal to the predetermined value.

18. The method of claim 15, further comprising:

before the setting of the representative value,

allowing the controller to perform a control operation to map continuous logical addresses to physical addresses of blocks of different planes.

19. A method of controlling a solid state storage system, comprising:

setting, in a write cycle, a representative value as a block allocation reference, and calculating, in the write cycle, a data value as life time information in according to predetermined information of each block in a current state;

determining whether there are blocks in which a deviation between the representative value and the data value is less than or equal to a predetermined value, when data is processed in accordance with a command from an external host; and

performing a write operation in blocks that correspond to having deviations between the representative value and the data value which are less than or equal to the predetermined value and allowing a controller to initialize information of all of the blocks when none of blocks have deviations between the representative value and the data value which are less than or equal to the predetermined value.

20. The method of claim 19,

wherein, when the data value is calculated, the write cycle is counted and the data value is set as the representative value that corresponds to a maximum number of write counts of the blocks.

21. The method of claim 19,

wherein, in the step of determining of whether any blocks have deviations between the representative value and the data value which are less than or equal to a predetermined value, a control operation is performed to determine the deviations and to preferentially allocate any blocks that having large deviations.

22. The method of claim 19, further comprising:

before the setting of the representative value,

allowing the controller to perform a control operation of mapping continuous logical addresses to physical addresses of blocks of different planes.