Management of Memory Blocks That Directly Store Data Files

• US 20070033328A1
• Filed: 05/08/2006
• 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 8,055,832 B2
• 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 16/1847 specifically adapted to static storage, e.g. adapted to flash memory or SSD
• CPC Class Codes: G06F 2212/7202 Allocation control and policies
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G06F 3/0605 by facilitating the interaction with a user or administrator
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0643 Management of files
• CPC Class Codes: G06F 3/0644 Management of space entities, e.g. partitions, extents, pools
• CPC Class Codes: G06F 3/0652 Erasing, e.g. deleting, data cleaning, moving of data to a wastebasket
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 16/102 External programming circuits, e.g. EPROM programmers; In-circuit programming or reprogramming; EPROM emulators

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. A type of memory block is selected to receive additional data of a file that depends upon the types of blocks into which data of the file have already been written. Blocks containing data are selected for reclaiming any unused capacity therefrom by a process that selects blocks in order starting with those containing the least amount of valid data.

Claims

1. A method of storing data in blocks of re-programmable non-volatile memory as uniquely identified files, which comprises:

maintaining a record for the individual stored files of one of a plurality of file states that are based upon how data of the file are distributed among one or more of a plurality of types of blocks, and

writing additional data of a given one of the files to a type of block that is selected based upon the state in the record of the given file.

2. The method of claim 1, wherein the record for an individual file includes an identification of any blocks of a type in which data of the file are stored along with data from another file.

3. The method of claim 1, wherein writing additional data additionally includes transitioning the state of the given file from a first state to second state, wherein the first and second file states are based upon storage of data of the given file in at least one different type of block.

4. The method of claim 1, wherein writing additional data additionally includes transitioning the state of the given file so that additional data of the given file are written to a type of block that limits the number of blocks in the memory that contain data of the file and also contain data of another file to be below a predetermined number.

5. The method of claim 1, wherein writing additional data includes writing data received from outside of the memory.

6. The method of claim 1, wherein writing additional data includes copying data from another location within the memory.

7. 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 uniquely identified files, comprising:

designating a set of a plurality of data block types in terms of a structure of file data stored within individual blocks so designated,

designating a set of a plurality of permitted file states in terms of a combination of types of one or more blocks in which data of individual files so designated are stored,

maintaining a record of the file states of individual data files stored in the memory system, and

writing data for an individual file to a type of block selected according to the current state of the file in the record.

8. The method of claim 7, wherein the designated plurality of data block types includes a first plurality of types in which data of only one file are stored in a single block and a second plurality of types in which data of two or more files are stored in a single block, and wherein the permitted file states limit a maximum number of blocks of the second plurality of types to which data of a single one of the files may be written.

9. The method of claim 8, wherein the maximum number is two.

10. The method of claim 7, wherein the memory storage cells are flash erasable.

11. The method of claim 10, wherein the memory storage cells individually include electrical charge storage elements.

12. The method of claim 10, wherein the electric storage elements are individually operated to store multiple levels of charge in order to store more than one bit of data.

13. A method of operating a non-volatile memory system with memory storage cells grouped into blocks of memory cells that are simultaneously erased prior to reprogramming and which stores data as a plurality of distinctly identified data files, comprising:

identifying blocks storing data of individual files by one of a plurality of types of blocks including a first type of block containing valid data of two or more files and a second type of block containing data of only one file,

designating one of a plurality of permitted states for individual files stored in one or more blocks of the memory system in terms of an allowed one or more types of the blocks,

maintaining a set of a plurality of permitted transitions between file states that limit a number of blocks of the first type that can store data of a single file in favor of blocks of the second type,

in response to a need to write additional data to an existing file stored in the memory, identify one of the blocks to which data of the existing file have most recently been written but if this identified block cannot accept additional data of the file then transition the state of the file to a next permitted state within the set of permitted file state transitions and identify an additional block having a type allowed by the next permitted state, and

thereafter writing the additional data to the type of block so identified.

14. The method of claim 13, wherein the set of plurality of permitted transitions between file states limit the number of blocks of the first type that can store data of a single file to two.

15. The method of claim 13, wherein writing additional data includes writing data received from a host system to which the memory is connected.

16. The method of claim 13, wherein writing additional data includes copying data from another location within the memory.

17. The method of claim 13, wherein the method is carried out in a portable memory card or drive.

18. A method of programming a distinctly identified data file into blocks of non-volatile memory cells that are characterized by being erased prior to reprogramming, comprising:

selecting one or more blocks in which to program a data file that maintains a number of blocks partially containing data of the file below a preset limit, and

programming data of the file into the selected one or more blocks.