Variable caching policy system and method

• US 20070174551A1
• Filed: 01/20/2006
• Published: 07/26/2007
• Est. Priority Date: 01/20/2006
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Herman, Kenneth, Cornwell, Michael, Dudte, Christopher
• Granted Patent: US 7,752,391 B2
• Time in Patent Office: Days
• US Class Current: 711/118
• CPC Class Codes: G06F 12/0888 using selective caching, e.g. bypass

Abstract

A method for managing data storage is described. The method includes receiving data from an external host at a peripheral storage device, detecting a file system type of the external host, and adapting a caching policy for transmitting the data to a memory accessible by the storage device, wherein the caching policy is based on the detected file system type. The detection of the file system type can be based on the received data. The detection bases can include a size of the received data. In some implementations, the detection of the file system type can be based on accessing the memory for file system type indicators that are associated with a unique file system type. Adapting the caching policy can reduce a number of data transmissions to the memory. The detected file system type can be a file allocation table (FAT) system type.

Claims

1. A method for managing data storage, comprising:

receiving data from an external host at a peripheral storage device;

detecting a file system type of the external host; and

adapting a caching policy for transmitting the data to a memory accessible by the storage device, wherein the caching policy is based on the detected file system type.

2. The method of claim 1, wherein the detection of the file system type is based on the received data.

3. The method of claim 2, wherein detection bases include a size of the received data.

4. The method of claim 1, wherein the detection of the file system type is based on accessing the memory for file system type indicators that are associated with a unique file system type.

5. The method of claim 1, wherein adapting the caching policy reduces a number of data transmissions to the memory.

6. The method of claim 1, wherein the detected file system type is a file allocation table (FAT) system type.

7. The method of claim 6, wherein the FAT system type is detected if the received data is equal to or less than a received data threshold.

8. The method of claim 6, further comprising accessing in the memory a FAT structure of the FAT system type adapted to specify a memory location of files or directories, storing the structure in a cache, and performing operations on the structure in the cache when the operations are addressed to the structure in the memory.

9. The method of claim 6, wherein the adapted caching policy comprises instructing a cache to store the received data until a flush cache signal is received, which initiates a transmission of at least a portion of the data to the memory.

10. The method of claim 9, wherein the flush cache signal is transmitted when a cache threshold is reached.

11. The method of claim 1, wherein the detected file system type is a Hierarchical File System (HFS) type.

12. The method of claim 11, wherein the file system type HFS type is detected if the received data is greater than a received data threshold.

15. The method of claim 1, wherein the detected file system type is a new technology file system (NTFS) type or a Linux file system type.

13. The method 11, wherein the adapted caching policy instructs a cache to operate as a segmented circular array adapted to write the data to segments of the array until a last segment is written and then to rewrite the segments with additional received data.

14. The method of 13, wherein the adapted caching policy further instructs the cache to transmit the data from a segment before the segment is rewritten.

16. An article of manufacture comprising machine-readable instructions operable to cause a data processing apparatus to:

receive information that conforms to a file system type from an external computing device;

determine the file system type; and

modify a caching policy based on the file system type, wherein the caching policy is related to caching at least a portion of the information for transfer to a memory.

17. The article of claim 16, wherein determining the file system type comprises selecting a default file system type unless another file system type is determined.

18. The article of claim 17, wherein the default file system type is a file allocation table (FAT) type.

19. The article of claim 18, wherein another file system type replaces the FAT system type if the received information exceeds a received information threshold.

20. The article of claim 19, wherein the received information threshold is 64 kilobytes.

21. The article of claim 16, further comprising receiving an indication of a connection with the external computing device and initiating the determination of the file system type in response to the indication.

22. The article of claim 21, further comprising resetting the caching policy to a default caching policy when the connection with the external computing device is terminated.

23. A system for managing data, comprising:

an interface for receiving information from an external host;

a cache for storing the information; and

a cache manager for determining a file system type associated with the information and for modifying a caching policy based on the file system type, wherein the caching policy is related to storage of the information in the cache and transfer of the information from the cache to a memory.

24. The system of claim 23, further comprising a battery operable to provide power to complete the transfer of the information from the cache to the memory after an external connection supplying power is interrupted.

25. The system of claim 23, wherein the memory is a rotational memory.

26. A system for managing a cache, comprising:

means for interfacing with data from an external host;

means for storing the received data; and

means for detecting a file system type used by the external host and for modifying a caching policy based on the file system type, wherein the caching policy is associated with transfers of the data to and from the means for storing.

27. The system of claim 26, wherein the data is transferred from the means for storing to a flash memory.

28. The system of claim 26, wherein the flash memory is a NAND flash memory.