Indexing of File Data in Reprogrammable Non-Volatile Memories That Directly Store Data Files

• US 20070033375A1
• Filed: 07/21/2006
• Published: 02/08/2007
• Est. Priority Date: 08/03/2005
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: Wright, Barry, Sinclair, Alan
• Granted Patent: US 7,949,845 B2
• Time in Patent Office: Days
• US Class Current: 711/203
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7201 Logical to physical mapping or translation of blocks or pages

Abstract

Host system data files are written directly to a large erase block flash memory system with a unique identification of each file and offsets of data within the file but without the use of any intermediate logical addresses or a virtual address space for the memory. Directory information of where the files are stored in the memory is maintained within the memory system by its controller, rather than by the host. Each data file is uniquely identified in a file directory, which points to entries in a file index table (FIT) of data groups that make up the file and their physical storage locations in the memory.

Claims

1. A method of operating a non-volatile memory system with storage cells grouped into blocks of memory cells that are erased prior to reprogramming with data of files received from outside the memory system, comprising:

store, in the memory blocks, data of files having unique file identifiers,

maintain, for individual files, records of the physical block locations of data of the individual files,

maintain a classification of the individual files as either (1) likely to be modified in the near future or (2) not likely to be modified in the near future,

maintain a directory of links to the records of the files by their unique file identifiers, the links being indirect for records of files classified as (1) and direct for records of files classified as (2), and

access a selected one of the records through the directory by use of its unique file identifier.

2. The method of claim 1, wherein a file is maintained in classification (1) while a host system to which the memory system is connected designates the individual file to be opened, and wherein a file is maintained in classification (2) while the host system to which the memory system is connected designates the individual file as closed.

3. The method of claim 1, wherein the file classifications are maintained by the memory system in response to the writing of file data within at least one of the memory blocks from a host to which the memory system is attached.

4. The method of claim 1, wherein the indirect link of a file includes an entry in the directory of an address of a first location in the memory that does not change as a second location containing the record of the file changes, the first location containing an address of the second location with any changes thereof, and wherein the direct link of a file includes an entry in the directory of an address of the second location.

5. The method of claim 1, wherein records of files classified as (1) are maintained in individual pages within the memory blocks without records of other files therein, and wherein multiple records of files classified as (2) are maintained in individual pages within the memory blocks.

6. The method of claim 1, wherein a number of records of files classified as (2) are grouped together in a first page of the memory blocks, and a number of links to those numbers of records are grouped together in a second page of the memory blocks forming the directory.

7. The method of claim 6, wherein the number of records of files classified as (2) stored in the first page are limited to files whose links are stored in the second page.

8. A method of operating a non-volatile memory system with storage cells grouped into blocks of memory cells that are erased prior to reprogramming with data files identified by unique file identifiers, comprising:

storing data of individual files as one or more data groups,

maintain records of the data groups that make up individual ones of the data files, and

maintain a directory of links to the records by the unique file identifiers, the links being direct for inactive files and indirect for active files.

9. The method of claim 8, wherein active files are those likely to be modified in the near future, and inactive files are those not likely to be modified in the near future.

10. The method of claim 8, wherein active files include files designated by a host to which the memory system is connected as opened, and inactive files include files designated by the host as closed.

11. The method of claim 8, wherein the memory system identifies the individual files as active or inactive by monitoring at least one pattern of storage of the files within the memory blocks.

12. The method of claim 8, wherein the one or more data groups include data in contiguous logical file offset addresses and contiguous physical addresses within memory cell blocks.

13. The method of claim 8, wherein records of active files are maintained in individual pages within the memory blocks without records of other files therein, and wherein multiple records of inactive files are maintained in individual pages within the memory blocks.

14. The method of claim 8, wherein a number of records of inactive files are grouped together in a first page of the memory blocks, and a number of links to those numbers of records are grouped together in a second page of the memory blocks forming the directory.

15. A method of operating a non-volatile memory system with storage cells grouped into blocks of memory cells that are erased prior to reprogramming pages of the blocks with data identified by a unique file identifier and an offset address within the file, comprising:

storing data of individual files as one or more data groups that individually specify data in contiguous logical file offset addresses and contiguous physical addresses within memory cell blocks,

maintain a set of entries in a table of the data groups of the individual files, and

maintain a file directory that links the files by their unique identifiers to the entries in the table of data of the files, the link being direct for data of closed files and indirect for data of open files.

16. The method of claim 15, wherein tables of open files are maintained in individual pages within the memory blocks without tables of other files therein, and wherein multiple records of closed files are maintained in individual pages within the memory blocks.

17. The method of claim 15, wherein a number of records of closed files are grouped together in a first page of the memory blocks, and a number of links to those numbers of records are grouped together in a second page of the memory blocks forming the directory.

18. A method of operating a non-volatile memory system with storage cells grouped into blocks of memory cells that are erased prior to reprogramming data in pages of the blocks, comprising:

store, in a first plurality of pages, data of files that individually have a unique file identifier,

maintain, in at least a second page, records of the physical page locations of data of the files stored in the first plurality of pages, and

maintain, in at least a third page, pointers to the locations of records in at least the second page, wherein the records in the second page are limited to those of the files whose pointers are stored in the third page.

19. The method of claim 18, wherein the pointers to the locations of records in at least the second page are associated with the unique identifiers of the files to which the records pertain.

20. The method of claim 18, wherein the first plurality of pages are located in a first group of one or more blocks, said at least a second page is located in a second group of one or more blocks, and said at least a third page is located in a third group of one or more blocks.

21. The method of claim 18, wherein the first plurality of pages are located in a first group of one or more blocks, and said at least a second page and said at least a third page are located in common blocks of a second group of one or more blocks.

22. The method of claim 18, wherein the first plurality of pages, said at least a second page and said at least a third page are located together in common blocks of a group of one or more blocks.

23. A method of operating a non-volatile memory system with storage cells grouped into blocks of memory cells that are erased prior to reprogramming data in pages of the blocks, comprising:

maintain, in at least a first page, records of the physical page locations of where data are stored, and

maintain, in at least a second page, pointers to the locations of records in at least the first page, wherein the records in the first page are limited to those pointed to by the pointers stored in the second page.

24. A method of operating a non-volatile memory system with storage cells grouped into blocks of memory cells that are erased prior to reprogramming with data of files in pages of the blocks, comprising:

store, in the memory blocks, data of files having unique file identifiers,

maintain, for individual files, records of the physical block locations of data of the individual files,

maintain a directory of links to the records of the files by their unique file identifiers, the directory links being to one or more locations of memory that contain a physical address of the records, and

access a selected one of the records through the directory by use of its unique file identifier, wherein records of individual files are maintained in individual pages without records of other files therein.