DISCARDABLE FILES

• US 20100153474A1
• Filed: 12/16/2008
• Published: 06/17/2010
• Est. Priority Date: 12/16/2008
• Status: Abandoned Application

• Current Assignee: SanDisk IL Ltd. (Western Digital Corporation)
• Original Assignee: SanDisk IL Ltd. (Western Digital Corporation)
• Inventors: HAHN, Judah GAMLIEL, KOREN, David, CARMELI, Ran, BRYANT-RICH, Donald RAY, RAINES, Moshe
• Application Number:
  US12/336,089
• Publication Number:
  US 20100153474A1
• Time in Patent Office: Days
• US Class Current: 707/812
• CPC Class Codes: G06F 16/1737 for reducing power consumption or coping with limited storage space, e.g. in mobile devices saving storage space on storage devices G06F3/0608; power saving in storage systems G06F3/0625

Abstract

Files stored, or to be stored, in a storage device are marked either as non-discardable or as discardable in a file system structure associated with a storage device. Each discardable file has associated with it a discarding priority level. A publisher file is permitted to be stored in the storage device only if storing the publisher file does not narrow a storage usage safety margin that is reserved for user files. User files are allowed to be stored in the storage device even if storing them narrows the storage usage safety margin but, in such cases, the storage usage safety margin is restored by removing one or more discardable files from the storage device. A discardable file is removed from the storage device if its discarding priority level equals or is higher than a predetermined discarding threshold value.

Claims

1. A method for managing a storage device, the method comprising:

a) receiving one or more requests to store one or more files in a storage area of a storage device;

b) marking each of the one or more files as discardable or as non-discardable, the marking of each file being done in a structure of a file system associated with the storage device; and

c) managing the storage of the one or more files in the storage area of the storage device based on the marking of one or more files in the structure of the file system.

2. The method as in claim 1, wherein managing the storage area includes any one or a combination of (i) restoring a storage usage safety margin by selectively removing one or more files marked as discardable, (ii) freeing a storage area by removing all files marked as discardable, and (iii) remapping clusters of a file to a lower-performance storage module.

3. The method as in claim 1, further comprising:

d) sending the marked file to the storage device.

4. The method as in claim 1, wherein marking a file of the one or more files as discardable includes assigning to the file a discarding priority level.

5. The method as in claim 4, wherein assigning the discarding priority level to the file is done by any one of:

(i) setting a corresponding value to m most significant bits in a file allocation table entry corresponding to the marked file, or (ii) setting a corresponding value to a data field in a file system entry corresponding to the marked file.

6. The method as in claim 5, wherein the corresponding value is an attribute of the file.

7. The method as in claim 5, wherein the value of the m most significant bits is set to 0 if the marked file is non-discardable, or to a value between 1 and 2^m−

1 if the marked file is discardable.

8. The method as in claim 7, wherein the non-zero value of the m most significant bits is a discarding priority level indicating the priority at which the marked file can or should be discarded from the storage device.

9. The method as in claim 7, wherein the value “

1”

denotes a file that is discardable with the lowest priority, and wherein the value “

2^m−

1”

denotes a file that is discardable with the highest priority.

10. The method as in claim 4, wherein the discarding priority level is assigned to the marked file according to any one of:

(i) anticipated usage of the file, (ii) anticipated revenue associated with using the file, (iii) the file'"'"'s type, (iv) the file'"'"'s size, (v) the file'"'"'s location in the storage device, and (vi) the file'"'"'s age.

11. The method as in claim 4, further comprising:

d) updating the discarding priority level of the marked file with each new request to store a file in the storage device.

12. The method as in claim 4, wherein updating the discarding priority level of the marked file is done independently from one or more new requests to store a file in the storage device.

13. The method as in claim 1, further comprising:

d) setting a discarding threshold value such that a discardable file stored in the storage device is discarded from the storage device if the file has associated with it a discarding priority level that equals or is higher than the discarding threshold value.

14. The method as in claim 1, further comprising:

d) receiving a request to store a new file in the storage device;

e) evaluating whether there is a free storage space on the storage device which is larger than a desired storage usage safety margin and if there is such a storage space, storing the new file in the free storage space;

f) if the free storage space on the storage device equals or is smaller than the desired storage usage safety margin, (i) searching for a discardable file within the storage device that can be deleted, and (ii) if such a file is found, deleting that file to extend the free storage space, or, if no such file is found, refraining from storing the new file; and

g) storing the new file in the extended free storage space if the size of the extended free storage space is larger than the desired storage usage safety margin, or, if the size of the extended free storage space is not larger than the desired storage usage safety margin, repeating steps e) and f).

15. The method as in claim 14, wherein a discardable file is deleted if a discarding priority level associated with it equals or is greater than a predetermined discarding threshold value.

16. A storage allocator for managing a storage device, comprising:

a communication interface to interface a storage device and a host of the storage device;

a memory unit for storing a file system associated with the storage device; and

a processor for managing the file system associated with the storage device,

wherein the processor is configured (i) to receive one or more requests to store one or more files in a storage area of the storage device, (ii) to mark the one or more files as discardable or as non-discardable, the marking of each file being done in a structure of the file system associated with the storage device, and (iii) to manage the storage of the one or more files in the storage area of the storage device based on the marking of one or more files in the associated structure of the file system.

17. The storage allocator as in claim 16, wherein the processor is further configured to send the marked files to the storage device.

18. The storage allocator of claim 16, wherein as part of marking a file as discardable the processor is further configured to assign to the file a discarding priority level.

19. The storage allocator of claim 18, wherein the processor assigns the discarding priority level to the marked file by any one of:

(i) setting a corresponding value to m most significant bits in a file allocation table entry corresponding to the marked file, or (ii) setting a corresponding value to a data field in a file system entry corresponding to the marked file.

20. The storage allocator of claim 19, wherein the processor sets the value of the m most significant bits to 0 if the marked file is non-discardable or to a value between 1 and 2^m−

1 if the marked file is discardable.

21. The storage allocator of claim 20, wherein the value “

1”

denotes a file that is discardable with the lowest priority, and wherein the value “

2^m−

1”

denotes a file that is discardable with the highest priority.

22. The storage allocator of claim 20, wherein the non-zero value of the m most significant bits is a discarding priority level indicating the priority at which the marked file can or should be discarded from the storage device.

23. The storage allocator of claim 18, wherein the processor assigns the discarding priority level to the marked file according to an anticipated usage of the file.

24. The storage allocator of claim 18, wherein the processor is further configured to update the discarding priority level of the marked file with each new request to store a file in the storage device.

25. The storage allocator of claim 18, wherein the processor is further configured to update the discarding priority level of the marked file independently from one or more new requests to store a file in the storage device.

26. The storage allocator of claim 17, wherein the processor deletes a file stored in the storage device if the file has associated with it a discarding level priority that equals or is greater than a predetermined discarding threshold value.

27. The storage allocator of claim 17, wherein, the processor is further configured to, responsive to receiving a request to store a new file in the storage device, evaluate the size of free storage space on the storage device and,

(i) if the evaluated size of the free storage space on the storage device is larger than a desired storage safety margin, to store the new file in the storage device, and

(ii) if it is not larger than the desired storage safety margin, to search for one or more discardable files within the storage device that can be deleted in order to extend the free storage space such that the size of the extended free storage space is larger than the desired storage safety margin and upon finding such files delete the found files and store the new file in the extended free storage space, or, if no such files are found, to refrain from storing the new file.

28. The storage allocator of claim 27, wherein the one or more discardable files can be deleted from the storage device if the discarding priority level associated with the discardable files equals or is greater than a predetermined discarding threshold value.

29. A storage system comprising:

a communication interface; and

a storage allocator for managing a file system associated with a storage device, the storage allocator including a processor for managing storage of one or more files in a storage area of the storage device,

wherein the processor is configured (i) to receive, via the communication interface, one or more requests to store one or more files in the storage area, (ii) to mark each of the one or more files as discardable or as non-discardable, the marking of each file being done in a structure of the file system, and (iii) to manage the storage of one or more files in the storage area based on the marking of one or more files in the structure of the file system.

30. The storage system as in claim 29, wherein the communication interface is integral to the storage allocator.

31. The storage system as in claim 29, further comprising a storage device that includes the storage area for storing one or more of the files.

32. The storage system as in claim 29, wherein the storage allocator further includes a memory unit for storing the file system locally.

33. The storage system of claim 29, further comprising a storage device and/or a host of the storage device, and wherein the storage allocator resides in the storage device or in the host of the storage device.