Variable caching policy system and method

• US 7,752,391 B2
• Filed: 01/20/2006
• Issued: 07/06/2010
• Est. Priority Date: 01/20/2006
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Cornwell, Michael J., Dudte, Christopher P., Herman, Kenneth L.
• Primary Examiner(s): TSAI, SHENG JEN
• Application Number:
  US11/335,968
• Publication Number:
  US 20070174551A1
• Time in Patent Office: 1,628 Days
• Field of Search: 711/118, 711/113
• 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 by the peripheral storage device a file system type of the external host based upon the received data, wherein the file system type identifies a systematic procedure for storing and organizing files on a storage medium;

adapting a caching policy of the peripheral storage device for caching the data received from the external host in a cache of the peripheral storage device and for writing the received data from the cache of the peripheral storage device to memory that is accessible by the peripheral storage device, wherein the caching policy is adapted based on the detected file system type of the external host, the caching policy defining a sequence in which the peripheral storage device caches data received from the external host and writes the cached data from the cache to the memory, and the caching policy for a first detected file system type defining a different sequence for caching and writing the data received from the external host than the caching policy for a second detected file system type;

caching the received data in the cache of the peripheral storage device in accordance with the adapted caching policy; and

writing the received data from the cache of the peripheral storage device to the memory that is accessible by the peripheral storage device in accordance with the adapted caching policy.

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 of the file system type is based on a size of the received data in relation to a threshold data size that is indicative of at least one type of file system.

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.

29. The method of claim 1, wherein the adapted caching policy specifies that the data is cached in a manner that is substantially similar to the systematic procedure for storing and organizing files used by the detected 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 of the external computing device based upon the received information, wherein the file system type identifies a systematic procedure for storing and organizing files on a storage medium;

modify a caching policy based on the determined file system type of the external computing device, wherein the caching policy is related to caching at least a portion of the information received from the external computing device in a cache of the article of manufacture and is further related to writing the received information from the cache to memory of the article of manufacture, and farther wherein the caching policy defines a sequence in which the information received from the external host is cached in the cache of the article of manufacture and written from the cache to the memory of the article of manufacture, the caching policy for a first detected file system type defining a different sequence for caching and writing the information received from the external host than the caching policy for a second detected file system type;

cache the received information in the cache of the article of manufacture in accordance with the modified caching policy; and

write the received information from the cache of the article of manufacture to the memory of the article of manufacture in accordance with the modified caching policy.

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, farther 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 caching the information received from the external host by the interface;

memory for storing the information received from the external host, wherein the received information is written to the memory from the cache; and

a cache manager for determining a file system type of the external host based upon the received information and for modifying a caching policy based on the determined file system type, wherein the file system type identifies a systematic procedure for storing and organizing files on a storage medium, and wherein the caching policy is related to caching the information received from the external host in the cache and is further related to writing the received information from the cache to the memory, and further wherein the caching policy defines a sequence in which the information received from the external host is cached in the cache and written from the cache to the memory, the caching policy for a first detected file system type defining a different sequence for caching and writing the information received from the external host than the caching policy for a second detected file system type, wherein the cache manager is configured to;

cache the received information in the cache in accordance with the adapted caching policy; and

write the received information from the cache to the memory in accordance with the adapted caching policy.

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 caching the data received from the external host by the interface;

means for storing the received data, wherein the received data is written to the means for storing the received data from the means for caching the received data; and

means for detecting a file system type used by the external host based upon the received data and for modifying a caching policy based on the file system type used by the external host, wherein the file system type identifies a systematic procedure for storing and organizing files on a storage medium, and wherein the caching policy is associated with caching the received data in the means for caching the received data and is further associated with writing the received data from the means for caching the received data to the means for storing the received data, and further wherein the caching policy defines a sequence in which the data received from the external host is cached in the means for caching and written from the means for caching to the means for storing, the caching policy for a first detected file system type defining a different sequence for caching and writing the data received from the external host than the caching policy for a second detected file system type, wherein the means for detecting the file system type is further configured to;

cache the received data in the means for caching the received data in accordance with the modified caching policy; and

write the received information from the means for caching the received data to the means for storing the received data in accordance with the modified caching policy.

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

28. A method for managing data storage, comprising:

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

detecting whether a file system type of the external host comprises a file allocation table (FAT) file system type or a hierarchical file system (HFS) file system type;

adapting a caching policy for caching the data received from the external host in a cache of the peripheral storage device and for writing the received data from the cache of the peripheral storage device to memory that is accessible by the peripheral storage device, wherein the caching policy is based on the detected file system type of the external host, and further wherein the adapted caching policy defines a sequence in which the peripheral storage device caches data received from the external host and writes the cached data from the cache to the memory, the caching policy for a first detected file system type defining a different sequence for caching and writing the data received from the external host than the caching policy for a second detected file system type;

caching the received data in the cache of the peripheral storage device in accordance with the adapted caching policy; and

writing the received data from the cache of the peripheral storage device to the memory that is accessible by the peripheral storage device in accordance with the adapted caching policy.