Indexing of file data in reprogrammable non-volatile memories that directly store data files

• US 7,949,845 B2
• Filed: 07/21/2006
• Issued: 05/24/2011
• Est. Priority Date: 08/03/2005
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Sinclair, Alan W., Wright, Barry
• Primary Examiner(s): Elmore; Stephen C
• Assistant Examiner(s): Giardino, Jr.; Mark A
• Application Number:
  US11/459,255
• Publication Number:
  US 20070033375A1
• Time in Patent Office: 1,768 Days
• Field of Search: 711/103, 711/4, 711/170
• US Class Current: 711/170
• 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 data storage memory cells grouped into physical blocks of memory cells that are erased together prior to reprogramming with data of files received from outside the memory system, comprising:

receive data of files that are individually identified by a unique file identifier and offsets of data within the file,

store, in the memory blocks, data of the received files,

maintain, for individual files, records of the physical block locations of data of the individual files by their unique file identifiers and offsets of data within 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, by;

in response to a first file being classified as likely to be modified in the near future, causing the links for records of the first file to be indirect, and

in response to a second file being classified as not likely to be modified in the near future, causing the links for records of the second file to be direct,

access individual one of the records through the directory by use of the unique file identifiers, and

read data of the received data files that are stored in those of the physical blocks of memory cells whose locations are maintained in the accessed records.

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 as 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 to the record of the first 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 first file changes, and wherein the direct link to the record of the second the includes an entry in the directory of an address of a third location that changes as a fourth location containing the record of the second file changes.

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 data storage memory cells grouped into physical blocks of non-volatile memory cells that are erased together prior to reprogramming with data files received from outside of the memory system, comprising:

receiving data of files that are individually identified by a unique file identifier and offsets of data within the file,

storing data of individual files in the blocks of non-volatile memory cells as one or more data groups,

maintain records of the data groups that make up individual ones of the data files, the records including an address of the blocks of memory cells in which the data groups are stored,

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

read data of the received data files that are stored in those of the physical blocks of memory cells whose locations are maintained in the accessed records.

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 data storage memory cells grouped into physical blocks of non-volatile memory cells that are erased together 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 in blocks of non-volatile memory cells 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 by their unique file identifiers and offsets of data within the individual files, and

maintain a file directory that links the files by their unique identifiers to the entries in the table of data groups 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.