Method and system for remote access to computer devices via client managed server buffers exclusively allocated to the client

• US 6,549,934 B1
• Filed: 03/01/1999
• Issued: 04/15/2003
• Est. Priority Date: 03/01/1999
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Peterson, Glenn R., Gamache, Rod, Massa, Michael T., Kusters, Norbert P.
• Primary Examiner(s): Sheikh, Ayaz
• Assistant Examiner(s): Tran, Philip B.
• Application Number:
  US09/260,194
• Time in Patent Office: 1,506 Days
• Field of Search: 709/203, 709/217, 709/219, 709/238-240, 709/231, 709/250, 709/223-224
• US Class Current: 709/203
• CPC Class Codes: H04L 49/90 Buffering arrangements
• CPC Class Codes: H04L 49/9042 Separate storage for different parts of the packet, e.g. header and payload
• CPC Class Codes: H04L 49/9052 with buffers of different sizes
• CPC Class Codes: H04L 49/9057 Arrangements for supporting packet reassembly or resequencing
• CPC Class Codes: H04L 49/9078 using an external memory or storage device
• CPC Class Codes: H04L 67/01 Protocols

Abstract

A method and system for providing remote access and control of devices such as disks, tape drives and modems across a network. A client driver intercepts I/O requests that are destined for a device which an application essentially considers a local device, such as for purposes of disk mirroring. The client driver queues and dequeues the I/O request, marshals it with header information and data, and sends it as a message to the server over one of possibly multiple connections to the server. A server driver unmarshalls the message, places it in a preallocated buffer as designated by the client, and generates an I/O request therefrom directed to the server device. The server responds with a completion status. The client side manages the server buffers, and the client classifies and partitions large requests into one or more segments that fit the server buffers. Sequential processing also may be ensured. The client also handles cancel operations on the remote device, and the client may also load balance across the multiple paths, by selecting a connection based on criteria including pending message size and dynamic performance measurements of the connections.

Claims

1. In a computer system having a client and server, a method for accessing a remote device of the server, comprising:

allocating a plurality of managed buffers at the server for exclusive use by the client and server;

receiving an I/O request at a client mechanism;

communicating a message corresponding to the I/O request to a server mechanism, the client managing the buffers at the server including designating a managed buffer for buffering data in the message, the server buffering at least some of the data in the message in the managed buffer designated by the client; and

passing information in the message from the server mechanism to a device driver associated with the remote device.

2. The method of claim 1 further comprising receiving a reply from the server including status information about the request.

3. The method of claim 2 wherein the reply from the server further includes data.

4. The method of claim 2 further comprising providing I/O completion information from the client mechanism in response to the I/O request received thereby.

5. The method of claim 1 wherein the client mechanism is a device object.

6. The method of claim 5 wherein the I/O request comprises an I/O request packet.

7. The method of claim 1 wherein the server mechanism is a device object.

8. The method of claim 1 further comprising writing data to the remote device.

9. The method of claim 1 further comprising reading data from the remote device.

10. The method of claim 1 wherein the remote device is a disk drive.

11. The method of claim 1 wherein communicating a message comprises marshalling the message at the client, sending the message to the server, receiving the message at the server, and unmarshalling the message at the server.

12. The method of claim 1 wherein communicating the message comprises, sending the message to the server and receiving the message at the server, and further comprising, receiving a result at the server from the device driver, converting the result to a reply message including status information, communicating the reply message to the client, receiving the reply message at the client, placing the result in a client-side buffer, and completing the I/O request by returning the status information from the client mechanism.

13. The method of claim 12 wherein the reply message includes data.

14. The method of claim 1 wherein marshalling the message includes adding a header to the request, and further comprising interpreting information in the header at the server.

15. The method of claim 1 further comprising, writing information corresponding to the message to the message into the managed buffer designated by the client.

16. The method of claim 1 further comprising the step of segmenting the I/O request into a plurality of requests corresponding thereto.

17. The method of claim 16 wherein the message corresponds to one of the plurality of requests, and further comprising communicating from the client to the server at least one other message corresponding to at least one other of the plurality of requests.

18. The method of claim 1 further comprising, tracking availability of each managed buffer at the client, and wherein the client designates the managed buffer based on the designated managed buffer being available.

19. The method of claim 1 further comprising receiving another I/O request at the client mechanism, communicating a second message corresponding to the other I/O request to the server mechanism via at least one of the managed buffers, and passing information from the second message from the server mechanism to the device driver.

20. The method of claim 19 further comprising identifying an ordering for passing information from the messages from the server mechanism to the device driver.

21. The method of claim 19 wherein the I/O request and the other I/O request have a sequence associated therewith, and further comprising, waiting at the client for a response from the server indicative of success with respect to the message before communicating the second message to the server mechanism.

22. The method of claim 19 wherein the I/O request and the other I/O request have a sequence associated therewith, and further comprising waiting at the server for the request that is earlier in the sequence to be submitted to the remote device.

23. The method of claim 1 wherein a plurality of communications paths are present between the client and the server, and further comprising selecting one of the paths for communicating the message.

24. The method of claim 23 wherein the performance of the communications paths are measured periodically for latency and bandwidth information.

25. The method of claim 24 wherein selecting one of the paths includes routing the message to one of the plurality of communication paths based on the data size of the request and the latency and bandwidth information.

26. The method of claim 23 further comprising detecting a failure of one of the plurality of paths, and selecting another of the plurality of paths.

27. The method of claim 23 further comprising detecting a failure of each of the plurality of paths, holding at least one message, and attempting to reconnect each path.

28. The method of claim 1 further comprising receiving a cancel request corresponding to a message.

29. The method of claim 28 further comprising transmitting the cancel request to the server.

30. The method of claim 28 wherein the message is queued at the client, and further comprising dequeuing the message in response to the cancel request.

31. The method of claim 28 further comprising segmenting the I/O request into a plurality of requests corresponding thereto, communicating at least one of the requests to the server as a message, and sending a cancel request for each message sent to the server.

32. The method of claim 1 wherein designating one of the managed buffers includes the client selecting a managed buffer based on at least one criterion related to the I/O request.

33. The method of claim 32 wherein selecting the managed buffer based on at least one criterion related to the I/O request comprises classifying the I/O request based on size data.

34. The method of claim 1 wherein the message corresponds to an I/O request for returning data, and wherein the server buffers data returned from the remote device in response to the I/O request in a managed buffer designated by the client.

35. The method of claim 1 wherein the message corresponds to an I/O request for writing data, and wherein write data is buffered by the server for writing to the remote device in a managed buffer designated by the client.

36. The method of claim 1 wherein the server uses a header buffer and a data buffer based on the client designating the managed buffer.

37. In a computer system having a client and server connected by a communication mechanism, a system for accessing a device of the server from the client, comprising, a client-side mechanism for allocating a plurality of managed buffers on the server, the managed buffers managed by the client for exclusive use by the client and server, a client-side driver for receiving an I/O request and preparing the I/O request as a message for communication, the message identifying a designated managed buffer on the server as designated by the client, the client-side driver connected to the communication mechanism for sending the message, a server-side mechanism connected to the communication mechanism for receiving the message, the server-side mechanism interpreting the message to place information therein into the designated managed buffer on the server, and the server-side mechanism passing information in the message to a device driver associated with the device of the server.

38. The system of claim 37 wherein the device driver provides a result to the server-side mechanism, the server-side mechanism converts the result to a reply message including status information and communicates the reply message to the client, the client receives the reply message, and the client places a corresponding result in a client-side buffer and completes the I/O request by returning the status information from the client driver.

39. The system of claim 38 wherein the reply message includes data.

40. The system of claim 37 wherein the I/O request comprises an I/O request packet, the client-side driver comprises a filter driver, and the server-side mechanism comprises a filter driver.

41. The system of claim 37 wherein the remote device is a disk drive.

42. The system of claim 37 wherein the communication mechanism includes a plurality of communications paths.

43. The system of claim 42 further comprising a mechanism for measuring the performance of the communications paths.

44. The system of claim 43 further comprising a selection mechanism for selecting one of the paths based on the performance thereof.

45. The system of claim 44 wherein the selection mechanism selects one of the plurality of paths based on a failure in another of the plurality of paths.

46. The system of claim 37 wherein the client-side driver includes a marshalling mechanism for preparing the message, and the server-side mechanism includes a mechanism for unmarshalling the message.

47. The system of claim 46 wherein the message includes a header, and wherein the designated managed buffer on the server is provided in the header.

48. The system of claim 46 wherein the message includes a retry number corresponding to a number of times the message has been sent.

49. The system of claim 37 wherein the message includes a sequence number, and wherein the server-side mechanism passes information from the messages to the device driver in an order based on the sequence number.

50. The system of claim 37 wherein the client includes a segmenting mechanism for segmenting the I/O request into a plurality of requests corresponding thereto.

51. The system of claim 37 wherein the client includes a tracking mechanism for tracking the availability of each managed buffer at the server.

52. The system of claim 51 wherein the client includes at least one queue for queuing a message for sending to the server when the tracking mechanism indicates a corresponding managed buffer at the server is not available.

53. The system of claim 37 wherein the client includes a client-side cancel mechanism for handling a cancel request corresponding to a message.

54. The system of claim 53 wherein the client transmits a message corresponding to the cancel request to the server, and the server includes a server-side cancel mechanism.

55. The system of claim 54 wherein the client includes a segmenting mechanism for segmenting the I/O request into a plurality of requests corresponding thereto, wherein some of the requests are sent as segmented messages to the server and other of the requests are queued as segmented messages in a queue of the client, and wherein the client-side cancel mechanism handles the cancel request by dequeuing the segmented messages in the queue and by sending a cancel message to the server for each segmented message sent to the server.

56. The system of claim 37 wherein the designated managed buffer is selected based on at least one criterion related to the I/O request.

57. The system of claim 37 wherein the designated managed buffer is selected to correspond to a size of the I/O request.

58. The system of claim 37 wherein the client includes a tracking mechanism for tracking the availability of each managed buffer at the server, and wherein the designated managed buffer is selected by the client based on the availability thereof.

59. The system of claim 37 wherein the message corresponds to an I/O request for returning data, and wherein the server buffers data returned from the remote device in response to the I/O request in a managed buffer designated by the client.

60. The system of claim 37 wherein the message corresponds to an I/O request for writing data, and wherein write data is buffered by the server for writing to the remote device in a managed buffer designated by the client.

61. The system of claim 37 wherein the server uses a header buffer and a data buffer based on the client designating the managed buffer.

62. The system of claim 37 wherein the server server-side mechanism comprises a hardware mechanism.

63. The system of claim 37 wherein the server server-side mechanism comprises a software driver.

64. In a computer system having a client and server, a method for accessing a remote device of the server, comprising, allocating a plurality of managed buffers at the server, the buffers managed by the client for exclusive use by the client and server, receiving an I/O request at a client mechanism, selecting at the client one of the managed buffets on the server, sending a message corresponding to the I/O request to the server, the message associated with information identifying to the server the managed buffer selected by the client for the message, receiving the message at the server, passing information in the message from the server mechanism to the remote device via the selected managed buffer, receiving result information at the server from the remote device, sending a reply message corresponding to the result information to the client, receiving the reply message at the client, and completing the I/O request at the client by returning status information corresponding to the result information from the client mechanism.

65. The method of claim 64 wherein the result information includes status information and data, and further comprising placing at least some of the data in a client-side buffer.

66. The method of claim 64 wherein selecting the managed buffer comprises classifying the I/O request.

67. The method of claim 64 further comprising, at the client, tracking availability of the managed buffers, and wherein selecting the managed buffer comprises selecting the managed buffer based on availability.

68. The method of claim 64 wherein the message corresponds to an I/O request for returning data, and wherein sending the reply message to the client includes sending returned data from a server buffer that corresponds to the managed buffer designated by the client.

69. The method of claim 64 wherein the message corresponds to an I/O request for writing data, and wherein write data is buffered by the server for writing to the remote device in a managed buffer designated by the client.

70. The method of claim 64 wherein the server uses a header buffer and a data buffer based on the client designating tile managed buffer.

71. A computer-readable medium having computer-executable instructions for performing a method, comprising:

allocating a plurality of managed buffers at a server for exclusive use by a client and the server;

receiving an I/O request at a client mechanism;

communicating a message corresponding to the I/O request to a server mechanism, the client managing the buffers at the server including designating a managed buffer for buffering data in the message, the server buffering at least some of the data in the message in the managed buffer designated by the client; and

passing information in the message from the server mechanism to a device driver associated with a remote device of the server.

72. A computer-readable medium having computer-executable instructions for performing a method, comprising, allocating a plurality of managed buffers at a server, the buffers managed by a client for exclusive use by the client and server, receiving an I/O request at a client mechanism, selecting at the client one of the managed buffers on the server, sending a message corresponding to the I/O request to the server, the message associated with information identifying to the server the managed buffer selected by the client for the message, receiving the message at the server, passing information in the message from the server mechanism to a remote device of the server via the selected managed buffer, receiving result information at the server from the remote device, sending a reply message corresponding to the result information to the client, receiving the reply message at the client, and completing the I/O request at the client by returning status information corresponding to the result information from the client mechanism.