Method for controlling storage system, and storage control apparatus

• US 20030221077A1
• Filed: 04/25/2003
• Published: 11/27/2003
• Est. Priority Date: 04/26/2002
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Satoyama, Ai, Tabuchi, Hideo, Yamamoto, Yasutomo, Ohno, Hiroshi, Eguchi, Yoshiaki, Nakano, Toshio, Arai, Kouji, Shimada, Akinobu
• Granted Patent: US 7,051,121 B2
• Time in Patent Office: Days
• US Class Current: 711/165
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 2212/312 In storage controller
• CPC Class Codes: G06F 3/0607 by facilitating the process of upgrading existing storage systems, e.g. for improving compatibility between host and storage device
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0635 by changing the path, e.g. traffic rerouting, path reconfiguration
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0665 at area level, e.g. provisioning of virtual or logical volumes
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD

Abstract

A method for controlling a storage system including a host computer, and a first and a second storage control apparatuses each receiving a data input/output request from the host computer and executing a data input/output process for a storage device in response to the request, comprises connecting a first communication path between the host computer and the first apparatus; connecting a second communication path between the first apparatus and the second apparatus; receiving by the first apparatus a first data input/output request from the host computer through the first path; when the first apparatus has judged that the first request is not for the first apparatus, transmitting by the first apparatus a second data input/output request corresponding to the first request, to the second apparatus through the second path; and by the second apparatus, receiving the second request and executing a data input/output process corresponding to the second request received.

Claims

1. A method for controlling a storage system including a host computer, and a first and a second storage control apparatuses each having a function for receiving a data input/output request transmitted from said host computer and executing a data input/output process for a storage device in response to said data input/output request received, comprising:

connecting a first communication path between said host computer and said first storage control apparatus to each other;

connecting a second communication path between said first storage control apparatus and said second storage control apparatus to each other;

receiving by said first storage control apparatus a first data input/output request transmitted from said host computer through said first communication path;

when said first storage control apparatus has judged that said first data input/output request is not to be handled by said first storage control apparatus, transmitting by said first storage control apparatus a second data input/output request corresponding to said first data input/output request, to said second storage control apparatus through said second communication path; and

by said second storage control apparatus, receiving said second data input/output request and executing a data input/output process corresponding to said second data input/output request received.

2. A method for controlling a storage system according to claim 1, wherein said second data input/output request conforms to the same data format as that of the data input/output request that said second storage control apparatus directly receives from said host computer.

3. A method for controlling a storage system according to claim 1, wherein said second data input/output request is transmitted and received in conformity with the same protocol as that used when said second storage control apparatus makes direct transmission to and direct reception from said host computer.

4. A method for controlling a storage system according to claim 1, further comprising:

storing in said first storage control apparatus information concerning a storage device for which said second storage control apparatus executes data input/output processes; and

based on the information concerning a storage device that said first storage control apparatus stores, determining by said first storage control apparatus whether or not to transmit said second data input/output request corresponding to said first data input/output request to said second storage control apparatus.

5. A method for controlling a storage system according to claim 4, wherein

said information concerning a storage device includes at least any one of management information of storage areas for one or more logic volume(s) organized on a storage area provided by said storage device, information concerning performance of said logic volume, information concerning storage capacities of said logic volume, and information concerning the remaining capacities of said logic volume.

6. A method for controlling a storage system according to claim 1, further comprising:

storing in said first storage control apparatus access limit information concerning a storage device for which said second storage control apparatus executes data input/output processes; and

when said first storage control apparatus has received said first data input/output request, determining by said first storage control apparatus whether or not to transmit said second data input/output request corresponding to said first data input/output request to said second storage control apparatus, by contrasting the contents of said first data input/output request with said access limit information.

7. A method for controlling a storage system according to claim 6, further comprising:

transmitting by said second storage control apparatus said access limit information to said first storage control apparatus; and

receiving and storing said access limit information by said first storage control apparatus.

8. A method for controlling a storage system according to claim 6 or 7, wherein

organizing by said second storage control apparatus one or more logic volume(s) on a storage area provided by said storage device for which said second storage apparatus executes data input/output processes;

storing in said first storage control apparatus a correlation X between IDs given to each of said host computers and IDs of said logic volume(s) to which each of said host computers can make access; and

determining by said first storage control apparatus whether or not to transmit said second data input/output request to said second storage control apparatus, by contrasting said correlation X with a correlation between an ID of a host computer which is a requester, described in said first data input/output request and said logic volume which is the target of said data input/output process of said request described in said first data input/output request.

9. A method for controlling a storage system according to claim 1, wherein

said first storage control apparatus comprises:

a communication interface for connecting said first storage control apparatus to said first and said second communication paths;

a CPU for executing a data input/output process for said storage device in response to said first data input/output request; and

a cache memory for storing data input to/output from said storage device during said data input/output process.

10. A method for controlling a storage system according to claim 1, wherein

said second storage control apparatus comprises:

a communication interface for connecting said second storage control apparatus to said second communication path;

a CPU for executing a data input/output process for said storage device in response to said second data input/output request; and

a cache memory for storing data input to/output from said storage device during said data input/output process.

11. A method for controlling a storage system according to claim 1, said second communication path including a plurality of routes, comprising:

receiving by said first storage control apparatus information concerning said second communication path from a relay apparatus existing on said second communication path; and

based on said information concerning said second communication path, determining by said first storage control apparatus a route along which said second data input/output request is transmitted to said second storage control apparatus.

12. A method for controlling a storage system according to claim 11, wherein

the determination of the route is carried out based on at least any one of the conditions of performance, reliability and stability of the plurality of paths grasped based on the information concerning said second communication path.

13. A method for controlling a storage system according to claim 11, wherein

said relay apparatus is at least any one of a Fiber Channel switch, a Fiber Channel director, a Fiber Channel hub, an iSCSI router and an iSCSI switch.

14. A method for controlling a storage system according to claim 11, wherein

said information concerning said second communication path is at least one of network topology information and in-network node information conforming to the Fiber Channel standard, the SCSI standard or the iSCSI standard.

15. A method for controlling a storage system according to claim 1, said first and said second storage control apparatuses each organizing one or more logic volume(s) on a storage area provided by said storage device for which said first and said second storage control apparatuses execute respective data input/output processes, said second storage control apparatus having a second logic volume which is the target of data input/output processes executed by said second storage control apparatus, said second logic volume storing data of said first logic volume which is the target of data input/output processes executed by said first storage control apparatus, comprising:

receiving a data input/output request from said host computer and updating the contents of said first logic volume in response to said data input/output request received by said first storage control apparatus;

transmitting by said first storage control apparatus to said second storage control apparatus a data input/output request instructing said second logic volume on execution of a data update process corresponding to the updating;

receiving said data input/output request and updating the contents of said second logic volume in response to said data input/output request received, by said second storage control apparatus; and

storing in said first storage control apparatus information for grasping data not yet reflected on a logic volume of said second logic volumes among the data in said first logic volume.

16. A method for controlling a storage system according to claim 15, wherein said information for grasping data not yet reflected is information describing whether or not the data in said first logic volume is reflected on said second logic volume for each of zones defined on a storage area on said first logic volume.

17. A method for controlling a storage system according to claim 15 or 16, further comprising:

transmitting by said first storage control apparatus to said second storage control apparatus a data write-in request directed to said second logic volume concerning data not yet reflected on said second logic volume, that has been grasped from the information for grasping the data not yet reflected; and

receiving said data input/output request and executing for said second logic volume a write-in process corresponding to said data write-in request by said second storage control apparatus.

18. A method for controlling a storage system according to claim 1, said first and said second storage control apparatuses each organizing one or more logic volume(s) on a storage area provided by a storage device for which said first and said second storage control apparatuses execute respective data input/output processes, further comprising:

when writing new data to a first logic volume for which said first storage control apparatus executes data input/output processes, transmitting by said first storage control apparatus to said second storage control apparatus a data write-in request of old data stored in the area to write the new data prior to the writing;

by said second storage control apparatus, receiving said data write-in request and writing the old data to said second logic volume which is the target of data input/output processes executed by said second storage control apparatus;

transmitting by said second storage control apparatus to said first storage control apparatus the storage position of the old data in said second logic volume; and

storing in said first storage control apparatus the storage position of the new data in said first logic volume and the storage position of the transmitted old data in said second logic volume, correlating the two storage positions with each other.

19. A method for controlling a storage system according to claim 1, said first and said second storage control apparatuses each organizing one or more logic volume (s) on a storage area provided by a storage device for which said first and said second storage control apparatuses execute respective data input/output processes, further comprising:

when said first storage control apparatus has received from said host computer a data write-in request of new data to said first logic volume for which said first storage control apparatus executes data input/output processes, transmitting by said first storage control apparatus said data write-in request of the new data to said second storage control apparatus without writing the new data to said first logic volume;

by said second storage control apparatus, receiving said data input/output request and writing the new data to said second logic volume for which said second storage control apparatus executes data input/output processes;

transmitting by said second storage control apparatus to said first storage control apparatus the storage position of the new data in said second logic volume; and

storing in said first storage control apparatus the storage position in said first logic volume which is the write-in destination of the new data and the storage position in said second logic volume of the new data transmitted, correlating the two storage positions with each other.

20. A method for controlling a storage system according to claim 19, further comprising:

transmitting by said first storage control apparatus a read-out request concerning the new data to said second storage control apparatus;

receiving the read-out request and transmitting to said first storage control apparatus the new data stored in said second logic volume, by said second storage control apparatus; and

storing in said first storage control apparatus the new data at a storage position of the new data in said first logic volume specified by the correlation.

21. A method for controlling a storage system according to claim 19, said first storage control apparatus having a cache memory used for data write-in to said storage device corresponding to said first logic volume, further comprising:

when said first storage control apparatus has received said data write-in request of the new data from said host computer, storing in said first storage control apparatus the new data in said cache memory; and

storing in said first storage control apparatus the new data stored in said cache memory at a storage position in said first logic volume specified by the correlation.

22. A method for controlling a storage system according to claim 19, said first storage control apparatus having a cache memory used for data write-in to said storage device corresponding to said first logic volume, further comprising:

when said first storage control apparatus has received the data write-in request of the new data from said host computer, storing by said first storage control apparatus the new data in said cache memory;

checking by said first storage control apparatus whether or not the new data is stored in said cache memory;

if it is stored, instead of transmitting the read-out request, storing by said first storage control apparatus the new data stored in said cache memory at a storage position in said first logic volume specified by the correlation; and

if it is not stored, by said first storage control apparatus, transmitting the read-out request concerning the new data to said second storage control apparatus and storing the new data transmitted as a response to the read-out request at a storage position in said first logic volume specified by the correlation.

23. A method for controlling a storage system according to claim 21 or 22, further comprising:

determining by said first storage control apparatus whether or not to store the new data in said cache memory depending on the status of use of said cache memory.

24. A method for controlling a storage system according to claim 1, said first and said second storage control apparatuses each organizing a logic volume on a storage area provided by said storage device for which said first and said second storage control apparatuses execute respective data input/output processes, further comprising:

executing by said first storage control apparatus a program which uses said first logic volume for which said first storage control apparatus executes data input/output processes and said second logic volume for which said second storage control apparatus executes data input/output process;

allowing by said first storage control apparatus the program to recognize said first logic volume as a target of a first use and said second logic volume as a target of a second use;

allowing by said first storage control apparatus the program to recognize said first logic volume as the target of the second use and said second logic volume as the target of the first use at a timing when the contents of said first logic volume are identical to the contents of said second logic volume.

25. A method for controlling a storage system according to claim 24, further comprising:

providing by the program a function for storing also in the other logic volume a copy of data stored in one of the first logic volume and the second logic volume; and

allowing by the first storage control apparatus the program to recognize the logic volume recognized as the copy source as copy destination and the logic volume recognized as the copy destination as copy source.

26. A method for controlling a storage system according to claim 24, further comprising:

providing by the program a function for storing new data in the first logic volume and, simultaneously, storing in the second logic volume old data stored in the read-out target area; and

allowing by the first storage control apparatus the program to recognize the logic volume recognized as the storage destination of the new data as a storage destination of the old data and the logic volume recognized as the storage destination of the old data as the storage destination of the new data.

27. A method for controlling a storage system according to claim 1, the first and the second storage control apparatuses each organizing logic volumes on a storage area provided by the storage device for which the first and the second storage control apparatuses execute respective data input/output processes, further comprising:

when the first storage control apparatus has received from said host computer a data write-in request for the second logic volume, creating by the first storage control apparatus a check code concerning write-in data of the write-in request;

transmitting by the first storage control apparatus to the second storage control apparatus a data write-in request for the second volume concerning the check code created; and

when the first storage control apparatus has transmitted to the second storage control apparatus a data read-out request concerning the data in the second logic volume and has received from the second storage control apparatus data in response to the data read-out request transmitted, by the first storage control apparatus, receiving the check code concerning the data together with the response data and executing a process for confirming the validity of the data using the check code.

28. A method for controlling a storage system including a host computer, and a first and a second storage control apparatuses each having a function for receiving a data input/output request transmitted from the host computer and executing a data input/output process for a storage device in response to the data input/output request received, comprising:

connecting a first communication path between said host computer and said first storage control apparatus to each other;

connecting a second communication path between said first storage control apparatus and said second storage control apparatus to each other;

receiving by said first storage control apparatus a first data input/output request transmitted from said host computer through said first communication path;

by said first storage control apparatus, analyzing a first command contained in the first data input/output request and creating a second command that the second storage control apparatus can execute corresponding to the first command;

by said first storage control apparatus, creating a second data input/output request containing the second command and transmitting the second data input/output request to the second storage control apparatus; and

by said second storage control apparatus, receiving the second data input/output request and executing for the storage device a data input/output process corresponding to the second input/output request.

29. A method for controlling a storage system according to claim 28, further comprising:

storing in said first storage control apparatus information concerning an access limit to the storage device for which the second storage control apparatus executes data input/output processes, determined by analyzing the first command contained in the first data input/output request; and

when the first storage control apparatus has received the first data input/output request directed to the storage device for which the second storage control apparatus executes data input/output processes, executing by said first storage control apparatus a process concerning the access limit to the first data input/output request in response to the access limit information.

30. A method for controlling a storage system according to claim 28, further comprising:

by said first storage control apparatus, analyzing the first command contained in the first data input/output request and creating the second command which is a data read-out command that the second storage control apparatus can execute;

transmitting by said first storage control apparatus to the second storage control apparatus the second data input/output request in which the second command is set;

by said second storage control apparatus, receiving the second data input/output request, executing the second command described in the second data input/output request, and transmitting the read out data to the first storage control apparatus; and

by said first storage control apparatus, receiving the data and transmitting the data to a third storage control apparatus connected communicatively to the first storage control apparatus.

31. A method for controlling a storage system including a host computer, and a first and a second storage control apparatuses each having a function for receiving a data input/output request transmitted from the host computer and executing a data input/output process for a storage device in response to the data input/output request received, comprising:

connecting a first communication path between said host computer and said first storage control apparatus to each other;

connecting a second communication path between said first storage control apparatus and said second storage control apparatus to each other;

receiving by said first storage control apparatus a first data input/output request transmitted from the host computer through the first communication path;

judging by said first storage control apparatus whether a first command contained in the first data input/output request is a command that the second storage control apparatus can execute or not by analyzing the first command;

if the first storage control apparatus judges that the command is a command that the second storage control apparatus cannot execute, by said first storage control apparatus, creating a second command, that the second storage control apparatus can execute, corresponding to the command, creating a second data input/output request containing the created second command and transmitting the second data input/output request to the second storage control apparatus; and

by said second storage control apparatus, receiving the second data input/output request and executing for the storage device a data input/output process corresponding to the second data input/output request.

32. A transfer storage control apparatus in a storage system, said storage system including a host computer connected to said transfer storage control apparatus through a first communication path, an ordinary storage control apparatus connected to said transfer storage control apparatus through a second communication path, said transfer and ordinary storage control apparatuses having a function for receiving a data input/output request transmitted from said host computer and executing a data input/output process for a storage device in response to the data input/output request received respectively, said transfer storage control apparatus comprising:

means for receiving a first data input/output request transmitted from said host computer through said first communication path; and

means for transmitting to said ordinary storage control apparatus through said second communication path a second data input/output request corresponding to the first data input/output request when it is judged that the first data input/output request is not to be handled by said transfer storage control apparatus.

33. A transfer storage control apparatus according to claim 32, further comprising:

means for storing information concerning a storage device for which said ordinary storage control apparatus executes data input/output processes; and

means for determining whether or not to transmit the second data input/output request corresponding to the first data input/output request, to said ordinary storage control apparatus based on the information concerning said storage device.

34. A storage control apparatus according to claim 32 or 33, comprising:

means for storing access limit information concerning said storage device for which said ordinary storage control apparatus executes data input/output processes; and

means for determining whether or not to transmit the second data input/output request to said ordinary storage control apparatus based on the access limit information of the first data input/output request.

35. A transfer storage control apparatus in a storage system, said storage system including a host computer connected to said transfer storage control apparatus through a first communication path, an ordinary storage control apparatus connected to said transfer storage control apparatus through a second communication path, said transfer and ordinary storage control apparatuses having a function for receiving a data input/output request transmitted from said host computer and executing a data input/output process for a storage device in response to the data input/output request received respectively, said transfer storage control apparatus comprising:

means for organizing a first logic volume which is organized on a storage area provided by said storage device for which said transfer storage control apparatus executes data input/output processes;

means for transmitting to said ordinary storage control apparatus a data write-in request of old data stored in a write-in area for new data prior to writing of the new data when the new data is written in said first logic volume; and

means for receiving a storage position of the old data in a second logic volume which is organized on the storage area provided by said storage device for which said ordinary storage control apparatus executes data input/output processes, transmitted from said ordinary storage control apparatus, and for storing the storage position of the new data in said first logic volume and the storage position of the received old data in said second logic volume, correlating the two storage positions with each other.

36. A transfer storage control apparatus in a storage system, said storage system including a host computer connected to said transfer storage control apparatus through a first communication path, an ordinary storage control apparatus connected to said transfer storage control apparatus through a second communication path, said transfer and ordinary storage control apparatuses having a function for receiving a data input/output request transmitted from said host computer and executing a data input/output process for a storage device in response to the data input/output request received respectively, said transfer storage control apparatus comprising:

means for organizing a first logic volume which is organized on a storage area provided by said storage device for which said transfer storage control apparatus executes data input/output processes;

means for transmitting a data write-in request of new data to said ordinary storage control apparatus without writing the new data to said first logic volume when said transfer storage control apparatus has received from said host computer the data write-in request of the new data directed to said first logic volume for which said transfer storage control apparatus executes data input/output processes; and

means for receiving a storage position of the new data in a second logic volume which is organized on a storage area provided by a storage device for which said ordinary storage control apparatus executes data input/output processes, transmitted from said ordinary storage control apparatus, and for storing the storage position which is the write-in destination of the new data in said first logic volume and the storage position of the received new data in said second logic volume, correlating the two storage positions with each other.

37. A transfer storage control apparatus according to claim 36, further comprising:

means for transmitting a read-out request concerning the new data to said ordinary storage control apparatus; and

means for receiving the new data stored in said second logic volume transmitted from said ordinary storage control apparatus that has received the read-out request and for storing the new data at a storage position of the new data in said first logic volume specified from the correlation.

38. A transfer storage control apparatus according to claim 36, further comprising:

a cache memory which is utilized upon writing of data to said storage device corresponding-to said first logic volume;

means for storing the new data in said cache memory when a data write-in request of the new data is received from said host computer; and

means for storing the new data stored in said cache memory at a storage position in said first logic volume specified by the correlation.

39. A transfer storage control apparatus according to claim 36, further comprising:

a cache memory which is utilized upon writing of data to said storage device corresponding to said first logic volume;

means for storing the new data in said cache memory when a data write-in request of the new data is received from said host computer; and

means for checking whether the new data is stored in said cache memory or not and, if it is stored, storing the new data stored in said cache memory at a storage position in said first logic volume specified by the correlation without transmitting the read-out request, and, if it is not stored, transmitting a read-out request concerning the new data to said ordinary storage control apparatus and storing the new data transmitted as a response to the transmitted read-out request at a storage position in said first logic volume specified by the correlation.

40. A transfer storage control apparatus according to claim 38 or 39, further comprising:

means for determining whether or not to store the new data in said cache memory depending on the status of use of said cache memory.

41. A transfer storage control apparatus in a storage system, said storage system including a host computer connected to said transfer storage control apparatus through a first communication path, an ordinary storage control apparatus connected to said transfer storage control apparatus through a second communication path, said transfer and ordinary storage control apparatuses having a function for receiving a data input/output request transmitted from said host computer and executing a data input/output process for a storage device in response to the data input/output request received respectively, said transfer storage control apparatus comprising:

means for organizing a first logic volume which is organized on a storage area provided by said storage device for which said transfer storage control apparatus executes data input/output processes;

means for executing a program which utilizes said first logic volume and a second logic volume which is organized on a storage area provided by said storage device for which said ordinary storage control apparatus executes data input/output processes; and

means for allowing the program to recognize said first logic volume as the target of a second use and said second logic volume as the target of a first use at a timing when the contents of said first logic volume are identical to the contents of said second logic volume in cases where said first logic volume is recognized by the program as a target of the first use and said second logic volume is recognized by the program as the target of the second use.

42. A transfer storage control apparatus according to claim 41, the program provides a function for storing a copy of data stored in one of said first logic volume and said second logic volume in the other logic volume, further comprising:

means for allowing the program to recognize said logic volume recognized as the copy source as copy destination and said logic volume recognized as the copy destination as copy source.

43. A transfer storage control apparatus according to claim 41, the program providing a function for storing new data in said first logic volume and, simultaneously, storing in said second logic volume old data stored in the write-in target area, further comprising:

means for allowing the program to recognize said logic volume recognized as the storage destination of the new data as a storage destination of the old data and said logic volume recognized as the storage destination of the old data as the storage destination of the new data.

44. A transfer storage control apparatus in a storage system, said storage system including a host computer connected to said transfer storage control apparatus through a first communication path, an ordinary storage control apparatus connected to said transfer storage control apparatus through a second communication path, said transfer and ordinary storage control apparatuses having a function for receiving a data input/output request transmitted from said host computer and executing a data input/output process for a storage device in response to the data input/output request received respectively, said transfer storage control apparatus comprising:

means for organizing a first logic volume which is organized on a storage area provided by said storage device for which said transfer storage control apparatus executes data input/output processes;

means for creating a check code concerning a received write-in data when a data write-in request directed to a second logic volume has been received from said host computer;

means for transmitting to said ordinary storage control apparatus a data write-in request, concerning the created check code, directed to said second logic volume which is organized on a storage area provided by said storage device for which said ordinary storage control apparatus executes data input/output processes; and

means for transmitting to said ordinary storage control apparatus a data read-out request concerning data in said second logic volume, for receiving a check code concerning the data together with the response data when the data in response to the data read-out request transmitted has been received from said ordinary storage control apparatus, and for executing a process for confirming the validity of the data using the check code.

45. A transfer storage control apparatus in a storage system, said storage system including a host computer connected to said transfer storage control apparatus through a first communication path, an ordinary storage control apparatus connected to said transfer storage control apparatus through a second communication path, said transfer and ordinary storage control apparatuses having a function for receiving a data input/output request transmitted from said host computer and executing a data input/output process for a storage device in response to the data input/output request received respectively, said transfer storage control apparatus comprising:

means for receiving a first data input/output request transmitted from said host computer through said first communication path;

means for analyzing a first command contained in the first data input/output request and creating a second command that said ordinary storage control apparatus can execute, corresponding to the first command; and

means for creating a second data input/output request containing the second command and transmitting the second data input/output command to said ordinary storage control apparatus.

46. A transfer storage control apparatus according to claim 45, further comprising:

means for storing information concerning an access limit to said storage device for which said ordinary storage control apparatus executes data input/output processes, determined by analyzing the first command contained in the first data input/output request; and

means for executing a process concerning the access limit for the first data input/output request in response to the access limit information when the first data input/output request directed to said storage device for which said ordinary storage control apparatus executes data input/output processes has been received.

47. A transfer storage control apparatus according to claim 45, further comprising:

means for providing communicative connection with a third storage control apparatus;

means for analyzing the first command contained in the first data input/output request and creating a second command which is a data read-out command that said ordinary storage control apparatus can execute;

means for transmitting to said ordinary storage control apparatus a second data input/output request in which the second command is set; and

means for receiving the data transmitted by said ordinary storage control apparatus in response to the second data input/output request and transmitting the data to said third storage control apparatus.

48. A storage control apparatus comprising:

a host computer connected to said transfer storage control apparatus through a first communication path, an ordinary storage control apparatus connected to said transfer storage control apparatus through a second communication path, said transfer and ordinary storage control apparatuses having a function for receiving a data input/output request transmitted from said host computer and executing a data input/output process for a storage device in response to the data input/output request received respectively, said transfer storage control apparatus comprising;

means for receiving a first data input/output request transmitted from said host computer through said first communication path;

means for judging whether or not a first command is a command that said ordinary storage control apparatus can execute by analyzing the first command contained in the first data input/output request;

means for creating a second command, that said ordinary storage control apparatus can execute, corresponding to the command when it is judged that the command is a command that said ordinary storage control apparatus cannot execute; and

means for creating a second data input/output request containing the second command and transmitting the second data input/output request to said ordinary storage control apparatus.