I/O cache with user configurable preload

• US 6,370,614 B1
• Filed: 01/26/1999
• Issued: 04/09/2002
• Est. Priority Date: 01/26/1999
• Status: Expired due to Term

• Current Assignee: SK Hynix Inc.
• Original Assignee: Motive Power, Inc.
• Inventors: Teoman, Deniz, Neil, John M.
• Primary Examiner(s): Nguyen, Hiep T.
• Application Number:
  US09/237,990
• Time in Patent Office: 1,169 Days
• Field of Search: 711/113, 711/117, 711/118, 711/122, 711/147, 709/218
• US Class Current: 711/113
• CPC Class Codes: G06F 12/0862 with prefetch
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 2212/311 In host system

Abstract

An apparatus and method for accessing data in a computer system. A relatively high-speed, intermediate-volume storage device is operated as a user-configurable cache. Requests to access a mass storage device such as a disk or tape are intercepted by a device driver that compares the access request against a directory of the contents of the user-configurable cache. If the user-configurable cache contains the data sought to be accessed, the access request is carried out in the user-configurable cache instead of being forwarded to the device driver for the target mass storage device. Because the user-cache is implemented using memory having a dramatically shorter access time than most mechanical mass storage devices, the access request is fulfilled much more quickly than if the originally intended mass storage device was accessed. Data is preloaded and responsively cached in the user-configurable cache memory based on user preferences.

Claims

1. In a computer system executing a computer operating system having a device driver stack, a method of responding to a request to access a storage location in a mass storage device, the method comprising:

determining whether data from the storage location is stored in a primary cache maintained in a system memory of the computer system;

determining whether the data from the storage location is stored in a secondary cache of the computer system in response to determining that the data is not stored in the primary cache; and

executing a first device driver to access the data in the secondary cache in response to determining that the data from the storage location is stored in the secondary cache, the first device driver being logically located in the device driver stack above a second device driver that controls access to the mass storage device.

2. The computer system of claim 1 wherein the secondary cache is maintained in a secondary memory of the computer system that is distinct from the system memory.

3. The method of claim 2 wherein the secondary memory is a non-volatile memory.

4. The method of claim 2 wherein the secondary memory is a solid state memory.

5. The method of claim 1 wherein determining whether the data from the storage location is stored in the secondary cache comprises executing a third device driver to determine contents of the secondary cache.

6. The method of claim 1 wherein the first device driver includes program code which, when executed, performs said determining whether the data from the storage location is stored in the secondary cache.

7. The method of claim 1 wherein executing the first device driver to access the data in the secondary cache comprises overwriting the data stored in the secondary cache with new data if the request to access the storage location is a write request.

8. The method of claim 7 further comprising deferring writing the new data back to the storage location in the mass storage device until a triggering event is detected.

9. The method of claim 8 wherein the triggering event is an elapse of a predetermined period of time.

10. The method of claim 7 further comprising encrypting the new data before overwriting the data stored in the secondary cache with the new data.

11. The method of claim 1 wherein executing the first device driver to access the data in the secondary cache comprises retrieving the data from the secondary cache if the request to access the storage location is a read request.

12. The method of claim 11 further comprising decrypting the data retrieved from the secondary cache.

13. The method of claim 1 further comprising comparing the data in the secondary cache against the data in the storage location in the mass storage device to determine whether the data in the storage location in the mass storage device has become corrupted.

14. The method of claim 13 further comprising signaling a user of the computer system that the data in the storage location in the mass storage device has become corrupted if the data in the secondary cache and the data in the storage location in the mass storage device do not match.

15. The method of claim 14 wherein signaling the user of the computer system comprises displaying an error message on a display of the computer system.

16. The method of claim 1 wherein the primary cache is an operating system (OS) cache.

17. The method of claim 1 further comprising invoking the second device driver to access the storage location in the mass storage device if the data has not been stored in the secondary cache.

18. The method of claim 17 further comprising caching the data in the secondary cache after invoking the second device driver to retrieve the data from the mass storage device.

19. The method of claim 1 further comprising receiving input from a user that indicates a characteristic of data to be stored in the secondary cache, and wherein determining whether the data from the storage location is stored in the secondary cache comprises determining whether the data requested to be accessed includes the characteristic indicated by the input from the user.

20. The method of claim 19 wherein receiving input from a user that indicates a characteristic of data to be stored in the secondary cache comprises receiving input from a user that indicates a source of data to be stored in the secondary cache.

21. The method of claim 20 wherein receiving input from a user that indicates a source of data to be stored in the secondary cache comprises receiving input from a user that indicates a mass storage volume that constitutes at least a portion of the mass storage device.

22. The method of claim 20 wherein receiving input from a user that indicates a characteristic of data to be stored in the secondary cache comprises receiving input from a user that indicates a file type.

23. The method of claim 22 wherein receiving input from a user that indicates a file type comprises receiving input from a user that indicates at least a portion of a filename.

24. The method of claim 23 wherein receiving input from a user that indicates at least a portion of a filename comprises receiving input from a user that indicates a file extension.

25. In a computer system executing a computer operating system having a device driver stack, a method comprising:

generating an access request to access data stored in a mass storage unit, access to the mass storage unit being controlled by a first device driver;

intercepting the access request in a second device driver, the second device driver being logically located above the first device driver in the device driver stack for the computer operating system;

determining in the second device driver whether the data has been stored in a secondary solid state memory that is distinct from a system memory of the computer system; and

redirecting the access request to access the data in the secondary solid state memory if the data has been stored therein.

26. The method of claim 25 wherein generating a request to access data stored in a mass storage unit comprises generating a request to access a file stored in the mass storage unit.

27. The method of claim 26 wherein generating a request to access a file stored in the mass storage unit comprises generating a request to access the file in a disk drive.

28. The method of claim 25 wherein determining in the second device driver whether the data has been stored in a secondary solid state memory comprises determining whether the data has been stored in a non-volatile solid state memory.

29. The method of claim 25 further comprising invoking the first device driver to retrieve the data from the mass storage unit if the data has not been stored in the secondary solid state memory.

30. The method of claim 29 further comprising caching the data in the secondary solid state memory after invoking the first device driver to retrieve the data from the mass storage unit.

31. The method of claim 25 further comprising receiving input from a user that indicates a characteristic of data to be stored in the secondary solid state memory, and wherein determining in the second device driver whether the data has been stored in the secondary solid state memory comprises determining whether the data requested to be accessed includes the characteristic of data stored in the secondary solid state memory.

32. The method of claim 31 wherein receiving input from a user that indicates a characteristic of data to be stored in the secondary solid state memory comprises receiving input from a user that indicates a source of data to be stored in the secondary solid state memory.

33. A method of accessing data in a computer system that includes a primary semiconductor memory, a secondary semiconductor memory, and at least one mass storage memory, and that executes a computer operating system having a device driver stack, the method comprising:

executing program code stored in the primary semiconductor memory to generate a request to access data stored in the mass storage device;

intercepting the request in a first device driver to determine whether the data is cached in the secondary semiconductor memory, the first device driver being logically located above a second device driver in the device driver stack;

accessing the data in the secondary semiconductor memory if the data is cached in the secondary semiconductor memory; and

forwarding the request to access the data to the second device driver to access the data in the mass storage device if the data is not cached in the secondary semiconductor memory.

34. The method of claim 33 wherein executing program code stored in the primary semiconductor memory to generate a request to access data comprises executing application program code to generate a request to access a data file stored in the mass storage device.

35. The method of claim 33 wherein executing program code stored in the primary semiconductor memory to generate a request to access data comprises executing operating system program code to generate a request to access a data file stored in the mass storage device.

36. The method of claim 33 wherein intercepting the request in a first device driver comprises detecting a request to invoke the second device driver and invoking the first device driver in response.

37. A computer system executing a computer operating system having a device driver stack, the computer system comprising:

a processing unit;

a system memory coupled to the processing unit;

a mass storage unit coupled to the processing unit;

a secondary solid state memory coupled to the processing unit; and

the system memory having stored therein program code that, when executed by the processing unit, causes the processing unit to;

determine whether data from a storage location in the mass storage unit is stored in a primary cache maintained in the system memory;

determine whether the data from the storage location is stored in a secondary cache in the secondary solid state memory in response to determining that the data is not stored in the primary cache; and

execute a first device driver defined by program code in the system memory to access the data in the secondary cache in response to determining that the data from the storage location is stored in the secondary cache, the first device driver being logically located in the device driver stack above a second device driver that controls access to the mass storage unit.

38. The computer system of claim 37 wherein the secondary solid state memory is a non-volatile memory.

39. The computer system of claim 37 wherein the primary cache is an operating system (OS) cache.

40. The computer system of claim 37 wherein the secondary solid state memory includes one or more dynamic random access memory (DRAM) devices.

41. The computer system of claim 37 wherein the secondary solid state memory is a battery-backed non-volatile memory that includes one or more dynamic random access memory (DRAM) devices.

42. A computer system executing a computer operating system having a device driver stack, the computer system comprising:

a processing unit;

a system memory coupled to the processing unit;

a network access device coupled to the processing unit and adapted to connect the computer system to a computer network that includes a remote mass storage device; and

a secondary solid state memory coupled to the processing unit; and

the system memory having stored therein program code that, when executed by the processing unit, causes the processing unit to;

determine whether the data from a storage location in the remote mass storage device is stored in a secondary cache in the secondary solid state memory in response to a request to access the remote mass storage device;

execute a first device driver defined by program code in the system memory to access the data in the secondary cache in response to determining that the data from the storage location is stored in the secondary cache, the first device driver being logically located in the device driver stack above a second device driver that controls access to the remote mass storage device.

43. The computer system of claim 42 wherein the secondary solid state memory is a non-volatile memory.

44. The computer system of claim 42 wherein the secondary solid state memory includes one or more dynamic random access memory (DRAM) devices.

45. The computer system of claim 42 wherein the network access device is adapted to connect the computer system to the computer network via a local area network and wherein the remote mass storage device is located in another computer system coupled to the local area network.

46. The computer system of claim 42 wherein the remote mass storage device is located in a web server computer that is configured to transmit data from the remote mass storage device according to a hyper-text transfer protocol (HTTP).

47. A computer system executing a computer operating system having a device driver stack, the computer system comprising:

a processing unit;

a mass storage unit coupled to the processing unit;

a non-volatile solid state memory coupled to the processing unit; and

a volatile solid state memory coupled to the processing unit, the volatile solid state memory having stored therein program code that, when executed by the processing unit, implements a first device driver to access the mass storage unit in response to data access requests, and a second device driver to intercept the data access requests prior to the data access requests being received by the first device driver, the second device driver determining, for each of the data access requests, whether data sought to be accessed by the request has been stored in the non-volatile semiconductor memory, the second device driver redirecting the access request to access the data in the secondary semiconductor memory instead of the mass storage unit if the data has been stored in the secondary semiconductor memory, the second device driver being logically located above the first device driver in the device driver stack.

48. The computer system of claim 47 wherein the non-volatile semiconductor memory is a battery-backed memory that includes one or more dynamic random access memory (DRAM) devices.

49. The computer system of claim 47 wherein the volatile semiconductor memory further has stored therein program code that, when executed by the processing unit, implements a user-interface to receive user input specifying data to be stored in the non-volatile semiconductor memory.

50. In a computer system executing a computer operating system having a device driver stack, a method of responding to a request to write a file to a mass storage device, the method comprising:

determining whether the data from the storage location is cached in a secondary cache of the computer system in response to determining that the data is not cached in a primary cache; and

executing a first device driver to write the file to the secondary cache in the computer system, the first device driver being logically located in the device driver stack above a second device driver that controls access to the mass storage device;

detecting when a number of contiguous storage blocks sufficient to store the file become available in the mass storage device of the computer system; and

copying the file from the cache to the number of contiguous storage blocks in response to detecting that the number of contiguous storage blocks have become available.