Method/apparatus for interfacing two remotely disposed devices coupled via transmission medium with first and second commands transmitted without first checking receiving device for readiness

• US 6,182,166 B1
• Filed: 08/25/1997
• Issued: 01/30/2001
• Est. Priority Date: 08/25/1997
• Status: Expired due to Term

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Shetty, Ramprasad, Vishlitzky, Natan, Ofek, Yuval, Shklarsky, Gadi
• Primary Examiner(s): Lee, Thomas C.
• Assistant Examiner(s): Nguyen, Tanh Q.
• Application Number:
  US08/918,238
• Time in Patent Office: 1,254 Days
• Field of Search: 707/9, 709/219, 709/237, 709/213, 711/100, 711/102, 714/1, 714/6, 714/13, 714/20, 714/752, 340/10.31, 370/313, 710/5, 710/33, 710/41
• US Class Current: 710/33
• CPC Class Codes: H04L 67/1095 Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]

Abstract

A method and apparatus for communicating a plurality of commands from a first device to a second device over a data communication link coupling the first and second devices, the plurality of commands including at least a first command and a second command. The first and second commands are transmitted over the data communication link from the first device to the second device in a single data transmission such that only a single propagation delay through the data communication link is incurred in transmitting both the first and second commands over the data communication link.

Claims

1. A method of communicating a plurality of commands from a first device to a second device over a data communication link coupling the first and second devices, the plurality of commands including at least a first command and a second command, the method comprising the step of:

(A) transmitting the first and second commands over the data communication link from the first device to the second device in a single data transmission such that only a single propagation delay through the data communication link is incurred in transmitting both the first and second commands over the data communication link, wherein the first and second commands are transmitted without first checking whether the second device is ready to receive the first and second commands.

2. The method of claim 1, wherein step (A) includes a step of transmitting the first and second commands over a data communication link that is a data communication line operable within a public communication network.

3. The method of claim 1, wherein step (A) includes a step of transmitting the first and second commands over a data communication link that is one of the family of T-carriers.

4. The method of claim 1, wherein the second device returns a status frame for each of the plurality of commands received at the second device, and wherein step (A) includes steps of:

transmitting the first command from the first device onto the data communication link; and

after transmitting the first command, transmitting the second command from the first device onto the data communication link without awaiting receipt at the first device of the status frame that corresponds to the first command and is returned from the second device when the first command is received at the second device.

5. The method of claim 4, wherein the plurality of commands further includes a third command, wherein each of the plurality of commands is directed to a target address associated with the second device, wherein when the second device receives one of the plurality of commands the second device determines whether the target address associated therewith is capable of processing the one of the plurality of commands and when it is not returns a status frame indicating that the one of the plurality of commands was not processed successfully, and wherein the method further includes steps of:

(B) transmitting the third command over the data communication link from the first device to the second device; and

(C) in response to receipt of a status frame indicating that the third command was not processed successfully, re-transmitting the third command over the data communication link from the first device to the second device.

6. The method of claim 4, further including steps of:

(B) setting a timer in conjunction with the transmitting of the second command over the data communication link;

(C) determining whether a status frame, indicating that the second command was received at the second device, is received at the first device before the timer expires; and

(D) when the timer expires without a status frame being received at the first device indicating that the second command was received at the second device, re-transmitting the second command over the data communication link from the first device to the second device.

7. The method of claim 4, further including a step of transmitting the status frame from the second device to the first device in response to receipt at the second device of the first command.

10. The method of claim 4, wherein each of the plurality of commands is directed to a target address associated with the second device, wherein the plurality of commands further includes a third command, and wherein the method further includes steps of:

(B) transmitting the third command over the data communication link from the first device to the second device;

(C) when the third command is received by the second device, determining whether the third command is capable of being processed by its corresponding target address; and

(D) when the third command is not capable of being processed by its corresponding target address when received by the second device, transmitting a status frame over the data communication link from the second device to the first device indicating that the third command was not processed successfully.

11. The method of claim 10, further including a step of:

(E) re-transmitting the third command over the data communication link from the first device to the second device in response to receipt of the status frame indicating that the third command was not processed successfully.

12. The method of claim 10, wherein step (D) includes a step of transmitting a status frame indicating that no additional commands directed to the target address of the third command should be sent to the second device until further notice.

13. The method of claim 12, further including a step of transmitting a second status frame over the data communication link from the second device to the first device when the target address to which the third command is directed is ready to receive additional commands.

14. The method of claim 13, further including a step of, in conjunction with transmitting the second status frame, flushing any commands received from the first device that are stored by the second device and have not yet been processed by the second device.

15. The method of claim 13, further including a step of discarding at the second device any commands received from the first device after the transmission of the second status frame and before receipt of a special status frame.

16. The method of claim 15, further including a step of transmitting a status accepted frame over the data communication link from the first device to the second device indicating that the second status frame was received at the first device.

17. The method of claim 16, further including a step of, after transmitting the status accepted frame, re-transmitting the third command over the data communication link from the first device to the second device.

18. The method of claim 17, wherein step (A) includes a step of transmitting the first and second commands over a data communication link that is a data communication line operable within a public communication network.

19. The method of claim 17, wherein the first device is a first storage system coupled to a central processing unit (CPU) and the second device is a second storage system.

20. The method of claim 1, wherein the second device includes a storage buffer capable of simultaneously storing no more than N commands received over the data link from the first device, wherein the plurality of commands includes a group of M commands, wherein M is greater than N, and wherein the method further includes a step of:

transmitting the group of M commands over the data communication link from the first device to the second device in a single data transmission.

21. The method of claim 20, further including a step of transmitting a status frame from the second device to the first device in response to receipt at the second device of each of the group of M commands.

22. The method of claim 20, wherein the first device is a first storage system coupled to a central processing unit (CPU) and the second device is a second storage system.

23. The method of claim 20, wherein step (A) includes a step of transmitting the first and second commands over a data communication link that is a data communication line operable within a public communication network.

24. The method of claim 1, wherein the first device is a first storage system coupled to a central processing unit (CPU) and the second device is a second storage system.

25. The method of claim 24, wherein step (A) includes a step of transmitting the first and second commands over a data communication link that is a data communication line operable within a public communication network.

91. The method of claim 1, wherein the first and second commands are transmitted without receiving, at the first device, a notification from the second device that the second device is ready to receive the first and second commands.

8. A method of communicating a plurality of commands from a first device to a second device over a data communication link coupling the first and second devices the plurality of commands including at least a first command, a second command, and a group of M commands, wherein the data communication link is bidirectional, the method comprising the steps of:

(A) transmitting the first and second commands over the data communication link from the first device to the second device in a single data transmission such that only a single propagation delay through the data communication link is incurred in transmitting both the first and second commands over the data communication link, wherein the second device returns a status frame for each of the plurality of commands received at the second device, wherein step (A) includes the steps of;

transmitting the first command from the first device onto the data communication link; and

after transmitting the first command, transmitting the second command from the first device onto the data communication link without awaiting receipt at the first device of the status frame that corresponds to the first command and is returned from the second device when the first command is received at the second device,

(B) transmitting the group of M commands over the data communication link from the first device to the second device; and

(C) following receipt of one of the group of M commands at the second device, transmitting a status frame corresponding to the one of the group of M commands over the data communication link from the second device to the first device while at least one other of the group of M commands is being transmitted over the data communication link from the first device to the second device.

9. A method of communicating a plurality of commands from a first device to a second device over a bidirectional data communication link coupling the first and second devices, the plurality of commands including at least a first command, a second command, and a group of M commands, wherein the second device returns a status frame for each of the plurality of commands received at the second device, the method comprising steps of:

(A) transmitting the first and second commands over the data communication link from the first device to the second device in a single data transmission such that only a single propagation delay through the data communication link is incurred in transmitting both the first and second commands over the data communication link;

(B) transmitting the group of M commands over the data communication link from the first device to the second device; and

(C) following transmission of one of the group of M commands over the data communication link from the first device to the second device, receiving a status frame corresponding to the one of the group of M commands over the data communication link at the first device from the second device while simultaneously transmitting at least one other of the group of M commands over the data communication link from the first device to the second device;

wherein the step (A) includes steps of;

transmitting the first command from the first device onto the data communication link; and

after transmitting the first command, transmitting the second command from the first device onto the data communication link without awaiting receipt at the first device of the status frame that corresponds to the first command and is returned from the second device when the first command is received at the second device.

26. A device for transmitting a plurality of commands to another device over a data communication link, the plurality of commands including at least a first command and a second command, the device comprising:

a transmitter to transmit the plurality of commands over the data communication link from the device to the another device by transmitting the first and second commands over the data communication link in a single data transmission such that only a single propagation delay through the data communication link is incurred in transmitting both the first and second commands over the data communication link, wherein the transmitter transmits the first and second commands without first checking whether the another device is ready to receive the first and second commands.

27. The device of claim 26, wherein the another device includes a command storage buffer capable of simultaneously storing no more than N commands received over the data link from the device, wherein the plurality of commands includes a group of M commands, wherein M is greater than N, and wherein the transmitter further includes:

means for transmitting the group of M commands over the data communication link from the device to the another device in a single data transmission.

28. The device of claim 26, wherein the device is a first storage system adapted to be coupled to a central processing unit (CPU) and the another device is a second storage system.

29. The device of claim 28, wherein the device is a disk drive storage system.

30. The device of claim 26, wherein the device is adapted to work with a data communication link that is a data communication line operable within a public communication network.

31. The device of claim 26, wherein the another device returns a status frame for each of the plurality of commands received at the another device, and wherein the transmitter further includes:

means for transmitting the first command from the device onto the data communication link; and

means for, after transmitting the first command, transmitting the second command from the device onto the data communication link without awaiting receipt at the device of the status frame that corresponds to the first command and is returned from the another device when the first command is received at the another device.

32. The device of claim 31, further comprising:

a plurality of timers;

means for setting each of the plurality of timers in conjunction with the transmitting of one of the plurality of commands over the data communication link;

means for determining, for each one of the plurality of commands, whether a status frame, indicating that the one of the plurality of commands was received at the another device, is received at the device before expiration of the timer corresponding to the one of the plurality of commands; and

means for, when one of the plurality of timers expires without a status frame being received at the device indicating that the corresponding one of the plurality of commands was received at the another device, re-transmitting the corresponding one of the plurality of commands over the data communication link from the device to the another device.

33. The device of claim 31, further comprising:

a timer;

means for setting the timer in conjunction with the transmitting of the second command onto the data communication link;

means for determining whether a status frame, indicating that the second command was received at the another device, is received at the device before the timer expires; and

means for, when the timer expires without a status frame being received at the device indicating that the second command was received at the another device, re-transmitting the second command over the data communication link from the device to the another device.

34. The device of claim 31, wherein the plurality of commands further includes a third command, wherein each of the plurality of commands is directed to a target address associated with the another device, wherein when the another device receives one of the plurality of commands the another device determines whether the target address associated therewith is capable of processing the one of the plurality of commands and when it is not the another device returns a status frame indicating that the one of the plurality of commands was not processed successfully, and wherein the transmitter further includes:

means for transmitting the third command over the data communication link from the device to the another device; and

means for, in response to receipt of a status frame indicating that the third command was not processed successfully, re-transmitting the third command over the data communication link from the device to the another device.

39. The device of claim 27, wherein each of the plurality of commands is directed to a target address associated with the another device, wherein when the another device receives one of the plurality of commands the another device determines whether the target address associated therewith is capable of processing the one of the plurality of commands and any additional commands and when it is not the another device returns a status frame indicating that the target address associated with the one of the plurality of commands is disconnected from the link and cannot receive any additional commands until further notice, and wherein the device further includes:

means, responsive to receipt of a status frame identifying a disconnected target address, for identifying the one of the plurality of commands directed to the disconnected target address as having not executed successfully, and for inhibiting the transmitter from transmitting any commands directed to the disconnected target address over the data communication link to the another device.

40. The device of claim 39, wherein the another device transmits a second status frame over the data communication link to the device when the disconnected target address is ready to receive additional commands, and wherein the device further includes means for transmitting a status accepted frame over the data communication link from the device to the another device indicating that the second status frame was received at the device.

41. The device of claim 40, wherein the device further includes means, responsive to receipt of the second status frame, for re-transmitting over the data communication link from the device to the another device the one of the plurality of commands that is directed to the disconnected target address and was identified as having not completed successfully.

92. The device of claim 26, wherein the transmitter transmits the first and second commands without receiving a notification from the another device that the another device is ready to receive the first and second commands.

35. A device for transmitting a plurality of commands to another device over a bidirectional data communication link, the plurality of commands including at least a first command, a second command, and a group of M commands, wherein the another device returns a status frame for each of the plurality of commands received at the another device, the device comprising:

transmitting means for transmitting the plurality of commands over the data communication link from the device to the another device, the transmitting means including;

means for transmitting the first and second commands over the communication link in a single data transmission such that only a single propagation delay through the data communication link is incurred in transmitting both the first and second commands over the data communication link, the first means including means for transmitting the first command from the device onto the data communication link and means for, after transmitting the first command, transmitting the second command from the device onto the data communication link without awaiting receipt at the device of the status frame that corresponds to the first command and is returned from the another device when the first command is received at the another device;

means for transmitting the group of M commands over the data communication link from the device to the another device; and

means for, following transmission of one of the group of M commands over the data communication link from the device to the another device, receiving a status frame corresponding to the one of the group of M commands over the data communication link at the device from the another device while simultaneously transmitting at least one other of the group of M commands over the data communication link from the device to the another device.

36. The device of claim 35, wherein the device is a first storage system adapted to be coupled to a central processing unit (CPU) and the another device is a second storage system.

37. The device of claim 35, wherein the device is adapted to work with a data communication link that is a data communication line operable within a public communication network.

38. The device of claim 37, wherein the device is a first storage system adapted to be coupled to a central processing unit (CPU) and the another device is a second storage system.

42. A communication system comprising:

a first device;

a second device; and

a data communication link coupling the first device to the second device;

wherein the first device includes a transmitter to transmit a plurality of commands to the second device over the data communication link, the plurality of commands including at least a first command and a second command by transmitting the first and second commands over the data communication link in a single data transmission such that only a single propagation delay through the data communication link is incurred in transmitting both the first and second commands over the data communication link, wherein the transmitter transmits the first and second commands without first checking whether the second device is ready to receive the first and second commands.

43. The communication system of claim 42, wherein the second device includes means for returning to the first device, over the data communication link, a status frame for each of the plurality of commands received at the second device.

44. The communication system of claim 43, wherein the transmitter includes:

means for transmitting the first command from the first device onto the data communication link; and

means for, after transmitting the first command, transmitting the second command from the first device onto the data communication link without awaiting receipt at the first device of the status frame that corresponds to the first command and is returned from the second device when the first command is received at the second device.

45. The communication system of claim 44, wherein the first device further comprises:

a plurality of timers;

means for setting each of the plurality of timers in conjunction with the transmitting of one of the plurality of commands from the first device over the data communication link;

means for determining, for each one of the plurality of commands, whether a status frame, indicating that the one of the plurality of commands was received at the second device, is received at the first device before expiration of the timer corresponding to the one of the plurality of commands; and

means for, when one of the plurality of timers expires without a status frame being received at the first device indicating that the corresponding one of the plurality of commands was received at the second device, re-transmitting the corresponding one of the plurality of commands over the data communication link from the first device to the second device.

46. The communication system of claim 44, wherein the first device further comprises:

a timer;

means for setting the timer in conjunction with the transmitting of the second command onto the data communication link;

means for determining whether a status frame, indicating that the second command was received at the second device, is received at the first device before the timer expires; and

means for, when the timer expires without a status frame being received at the first device indicating that the second command was received at the second device, re-transmitting the second command over the data communication link from the first device to the second device.

47. The communication system of claim 43, wherein the data communication link is a data communication line operable within a public communication network.

48. The communication system of claim 47, wherein the first device is a first storage system for storing information and the second device is a second storage system, wherein the communication system further includes a central processing unit coupled to the first device, and wherein the communication system further includes mirroring means, distributed between the first and second storage systems, for mirroring at least some of the information stored in the first storage system in the second storage system.

49. The communication system of claim 42, wherein the data communication link is a data communication line operable within a public communication network.

50. The communication system of claim 49, wherein the data communication link is one of the family of T-carriers.

52. The communication system of claim 42, wherein:

each of the plurality of commands is directed to a target address associated with the second device; and

the second device includes means, responsive to the second device receiving one of the plurality of commands over the data communication link, for determining whether the target address associated with the one of the plurality of commands is capable of processing the one of the plurality of commands and when it is not for returning a status frame to the first device indicating that the one of the plurality of commands was not processed successfully.

53. The communication system of claim 52, wherein:

the plurality of commands further includes a third command;

the transmitter in the first device includes means for transmitting the third command over the data communication link from the first device to the second device; and

the first device further includes means for, in response to receipt of a status frame indicating that the third command was not processed successfully, re-transmitting the third command over the data communication link from the first device to the second device.

54. The communication system of claim 42, wherein:

each of the plurality of commands is directed to a target address associated with the second device;

the second device includes means, responsive to receipt of one of the plurality of commands, for determining whether the target address associated with the one of the plurality of commands is capable of processing the one of the plurality of commands and any additional commands and when it is not for returning to the first device a status frame indicating that the target address associated with the one of the plurality of commands is disconnected from the link and cannot receive any additional commands until further notice.

55. The communication system of claim 54, wherein the first device includes means, responsive to receipt of a status frame identifying a disconnected target address, for identifying the one of the plurality of commands directed to the disconnected target address as having not executed successfully, and for inhibiting the transmitter from transmitting any commands directed to the disconnected target address.

56. The communication system of claim 55, wherein the second device includes means for transmitting a second status frame over the data communication link to the first device when the disconnected target address is ready to receive additional commands.

57. The communication system of claim 56, wherein the first device further includes means for transmitting a status accepted frame over the data communication link to the second device indicating that the second status frame was received at the first device.

58. The communication system of claim 57, wherein the first device further includes means, responsive to receipt of the second status frame, for re-transmitting over the data communication link from the first device to the second device the one of the plurality of commands that is directed to the disconnected target address and was identified as having not completed successfully.

59. The communication system of claim 58, wherein the first device is a first storage system for storing information and the second device is a second storage system, wherein the communication system further includes a central processing unit coupled to the first device, and wherein the communication system further includes mirroring means, distributed between the first and second storage systems, for mirroring at least some of the information stored in the first storage system in the second storage system.

60. The communication system of claim 59, wherein the data communication link is a data communication line operable within a public communication network.

61. The communication system of claim 42, wherein the first device is a first storage system for storing information and the second device is a second storage system, and wherein the communication system further includes a central processing unit coupled to the first device.

62. The communication system of claim 61, wherein the data communication link is a data communication line operable within a public communication network.

63. The communication system of claim 61, further including mirroring means, distributed between the first and second storage systems, for mirroring at least some of the information stored in the first storage system in the second storage system.

64. The communication system of claim 63, wherein the data communication link is a data communication line operable within a public communication network.

65. The communication system of claim 63, wherein the mirroring means includes:

first means, disposed in the first storage system, for transmitting the at least some of the information stored in the first storage system to the second storage system; and

second means, disposed in the second storage system, for storing in the second storage system the at least some of the information transmitted from the first storage system.

66. The communication system of claim 65, wherein the mirroring means further includes:

third means, disposed in the first storage system, for transmitting a request to the second storage system to transmit at least one information frame stored in the second storage system to the first storage system; and

fourth means, disposed in the second storage system, for transmitting the at least one information frame to the first storage system in response to receipt of the request.

93. The communication system of claim 42, wherein the transmitter transmits the first and second commands without receiving a notification from the second device that the second device is ready to receive the first and second commands.

51. A communication system comprising:

a first device;

a second device; and

a bidirectional data communication link coupling the first device to the second device;

wherein the first device includes transmitting means for transmitting a plurality of commands to the second device over the data communication link, the plurality of commands including at least a first command, a second command, and a group of M commands;

wherein the transmitting means includes means for transmitting the first and second commands over the data communication link in a single data transmission such that only a single propagation delay through the data communication link is incurred in transmitting both the first and second commands over the data communication link;

wherein the transmitting means in the first device includes means for transmitting the group of M commands over the data communication link from the first device to the second device; and

wherein the second device includes means, responsive to receipt of one of the group of M commands at the second device, for transmitting a status frame corresponding to the one of the group of M commands over the data communication link to the first device while the first device is simultaneously transmitting at least one other of the group of M commands over the data communication link to the second device.

67. A communication system comprising:

a first device;

a second device; and

a data communication link coupling the first device to the second device;

wherein the first device includes a transmitter to transmit a plurality of commands to the second device over the data communication link, the plurality of commands including at least a first command and a second command, by transmitting the first and second commands over the data communication link in a single data transmission such that only a single propagation delay through the data communication link is incurred in transmitting both the first and second commands over the data communication link; and

wherein;

the plurality of commands includes a group of M commands;

the second device includes a command storage buffer capable of simultaneously storing no more than N commands received over the data link from the first device, wherein M is greater than N; and

the transmitter in the first device includes means for transmitting the group of M commands over the data communication link from the first device to the second device in a single data transmission.

68. The communication system of claim 67, wherein the first device is a first storage system for storing information and the second device is a second storage system, wherein the communication system further includes a central processing unit coupled to the first device, and wherein the communication system further includes mirroring means, distributed between the first and second storage systems, for mirroring at least some of the information stored in the first storage system in the second storage system.

69. The communication system of claim 68, wherein the data communication link is a data communication line operable within a public communication network.

70. A device for receiving a plurality of commands from another device over a data communication link, the plurality of commands including at least a first command and a second command, the device comprising:

receiving means for receiving the plurality of commands over the data communication link from the another device, the receiving means including means for receiving the first and second commands over the data communication link in a single data transmission such that only a single propagation delay through the data communication link is incurred in receiving both the first and second commands over the data communication link, wherein the receiving means includes means for receiving the first and second commands without first indicating to the another device that the device is ready to receive the first and second commands.

71. The device of claim 70, wherein the device includes a command storage buffer capable of simultaneously storing no more than N commands received over the data link from the another device, wherein the plurality of commands includes a group of M commands, wherein M is greater than N, and wherein the receiving means further includes:

means for receiving the group of M commands over the data communication link from the another device in a single data transmission.

72. The device of claim 70, wherein the device is a first storage system and the another device is a second storage system adapted to be coupled to a central processing unit (CPU).

73. The device of claim 72, wherein the device is a disk drive storage system.

74. The device of claim 72, wherein the device is adapted to work with a data communication link that is a data communication line operable within a public communication network.

94. The device of claim 70, wherein the receiving means includes means for receiving the first and second commands without first sending a notification to the another device that the device is ready to receive the first and second commands.

75. A method of communicating a plurality of data transfers from a first device to a second device over a data communication link coupling the first and second devices, the plurality of data transfers including at least a first data transfer and a second data transfer, the first data transfer requiring that a response be transmitted from the second device to the first device, the method comprising steps of:

(A) transmitting the first data transfer over the data communication link from the first device to the second device; and

(B) transmitting the second data transfer over the data communication link from the first device to the second device without awaiting receipt at the first device of the response to the first data transfer;

wherein the first and second data transfers are transmitted without first checking that the second device is ready to receive the first and second data transfers.

76. The method of claim 75, wherein step (A) includes a step of transmitting the first data transfer over a data communication link that is a data communication line operable within a public communication network;

and wherein step (B) includes a step of transmitting the second data transfer over the data communication line operable within a public communication network.

77. The method of claim 75, wherein the second device includes a storage buffer capable of simultaneously storing no more than N data transfers received over the data link from the first device, wherein the plurality of data transfers includes a group of M data transfers, wherein M is greater than N, and wherein the method further includes a step of:

transmitting the group of M data transfers over the data communication link from the first device to the second device in a single data transmission.

78. The method of claim 75, wherein the first device is a first storage system coupled to a central processing unit (CPU) and the second device is a second storage system.

79. The method of claim 78, wherein step (A) includes a step of transmitting the first data transfer over a data communication link that is a data communication line operable within a public communication network;

and wherein step (B) includes a step of transmitting the second data transfer over the data communication line operable within a public communication network.

95. The method of claim 75, wherein the first and second data transfers are transmitted without receiving, at the first device, a notification from the second device that the second device is ready to receive the first and second data transfers.

80. A method of communicating a plurality of data transfers from a first device to a second device over a data communication link coupling the first and second devices, the plurality of data transfers including at least a first data transfer and a second data transfer, the first data transfer requiring that a response be transmitted from the second device to the first device, the method comprising steps of:

(A) transmitting the first data transfer over the data communication link from the first device to the second device; and

(B) transmitting the second data transfer over the data communication link from the first device to the second device without awaiting receipt at the first device of the response to the first data transfer;

wherein the second device includes a plurality of target addresses,

wherein step (A) includes a step of transmitting the first data transfer to a first of the plurality of target addresses; and

wherein step (B) includes a step of transmitting the second data transfer to a second of the plurality of target addresses that is different than the first of the plurality of target addresses.

81. The method of claim 80, wherein steps (A) and (B) include a step of transmitting the first and second data transfers over the data communication link from the first device to the second device in a single data transmission.

82. The method of claim 81, wherein the first device is a first storage system coupled to a central processing unit (CPU) and the second device is a second storage system.

83. The method of claim 82, wherein step (A) includes a step of transmitting the first data transfer over a data communication link that is a data communication line operable within a public communication network;

and wherein step (B) includes a step of transmitting the second data transfer over the data communication line operable within a public communication network.

84. A device for transmitting a plurality of data transfers to another device over a data communication link, the plurality of data transfers including at least a first data transfer and a second data transfer, the first data transfer requiring that a response be transmitted from the another device to the device, the device comprising:

a transmitter to transmit the plurality of data transfers over the data communication link from the device to the another device with the first data transfer being transmitted prior to the second data transfer by transmitting the second data transfer over the data communication link without awaiting receipt at the device of the response to the first data transfer, wherein the transmitter transmits the first and second data transfers without first checking that the another device is ready to receive the first and second data transfers.

85. The device of claim 84, wherein the device is a first storage system adapted to be coupled to a central processing unit (CPU) and the another device is a second storage system.

86. The device of claim 85, wherein the device is adapted to work with a data communication link that is a data communication line operable within a public communication network.

96. The device of claim 84, wherein the transmitter transmits the first and second data transfers without receiving a notification from the another device that the another device is ready to receive the first and second data transfers.

87. A device for transmitting a plurality of data transfers to another device over a data communication link, the plurality of data transfers including at least a first data transfer and a second data transfer, the first data transfer requiring that a response be transmitted from the another device to the device, the device comprising:

transmitting means for transmitting the plurality of data transfers over the data communication link from the device to the another device with the first data transfer being transmitted prior to the second data transfer, the transmitting means including means for transmitting the second data transfer over the data communication link without awaiting receipt at the device of the response to the first data transfer;

wherein the device is a first storage system adapted to be coupled to a central processing unit (CPU) and the another device is a second storage system;

wherein the another device includes a plurality of target addresses, and

wherein the transmitting means includes means for transmitting the first data transfer to a first of the plurality of target addresses and the second data transfer to a second of the plurality of target addresses that is different than the first of the plurality of target addresses.

88. The device of claim 87, wherein the transmitter includes means for transmitting the first and second data transfers over the data communication link in a single data transmission.

89. A device for transmitting a plurality of data transfers to another device over a data communication link, the plurality of data transfers including at least a first data transfer and a second data transfer, the first data transfer requiring that a response be transmitted from the another device to the device, the device comprising:

transmitting means for transmitting the plurality of data transfers over the data communication link from the device to the another device with the first data transfer being transmitted prior to the second data transfer, the transmitting means including means for transmitting the second data transfer over the data communication link without awaiting receipt at the device of the response to the first data transfer;

wherein the another device includes a plurality of target addresses, and wherein the transmitting means includes means for transmitting the first data transfer to a first of the plurality of target addresses and the second data transfer to a second of the plurality of target addresses that is different than the first of the plurality of target addresses.

90. The device of claim 89, wherein the transmitter includes means for transmitting the first and second data transfers over the data communication link in a single data transmission.