JP2004164657A - Multicomputer system and compound i/o system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To back up data of an I/O subsystem for opening into a backup system for main frame management not directly connected to the I/O subsystem. <P>SOLUTION: For connecting B-system I/O subsystems (113 and 114) for an open system to A-system I/O subsystems (104 and 105) for a main frame via a communication means and backing up the data of a disk connected to the B-system I/O subsystem into an MT library system, the A-system I/O subsystems are provided with tables (314 and 315) for allocating an unoccupied storage device address inside their own subsystems to a storage device in the I/O subsystem for the open system so that the data in the B-system I/O subsystem are made to be accessible from the main frame. A request in a variable length storage format received from the main frame is converted into a B-system fixed length storage format, and on the basis of the tables, access is made to a designated disk, and then, acquired data are fed to the main frame to be backed up into the backup system. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a system capable of backing up data in a storage device between a host computer and an I / O subsystem that cannot be directly connected due to different access interfaces, and a plurality of I / Os having different access interfaces to the host computer. Regarding the system to which the subsystem is connected.

  The mainframe has a data management function for optimal data placement and efficient operation support for a large-scale storage tier (storage tier) combining external storage devices with different processing speeds and storage capacities. The integrated storage management function is substantial, for example, corresponds to IBM's DFSMS (Data Facility Storage Management System), and details are described in Non-Patent Document 1.

  Through this management function, the disk data of the I / O subsystem of the mainframe can be backed up to a medium such as a magnetic tape or a magnetic tape library capable of storing low-cost or large-capacity data.

  On the other hand, open systems such as personal computers and workstations do not have a medium such as a magnetic tape or a magnetic tape library capable of storing a large amount of data such as a main frame.

  In general, open systems such as personal computers and workstations access the disk in accordance with a fixed-length record format, and the mainframe accesses the disk in accordance with a variable-length record format called a count key data format. ing.

  For this reason, the disk subsystem for the main frame and the disk subsystem for the open system are often configured separately.

  On the other hand, Patent Literature 1 discloses a technique for transmitting and receiving data between I / O subsystems.

U.S. Pat. No. 5,155,845

IBM Systems JOURNAL, Vol. 28, No1, 1989

  Since the host computers are different, the disk subsystem for the open system and the disk subsystem for the mainframe individually operate and manage backup and the like. However, as described above, since the open system does not have a medium such as a magnetic tape or a magnetic tape library capable of storing a large amount of data, it is effective to make a backup in the I / O subsystem of the mainframe. However, the disk system for an ordinary open system cannot be directly connected to the main frame because the interface is different.

  On the other hand, Patent Document 1 does not describe how to implement read / write processing for a storage system that is not directly connected to a host computer.

  An object of the present invention is to provide a system for backing up data in a storage device between a host computer and an I / O subsystem that cannot be directly connected due to different access interfaces. In particular, an object is to provide a system for backing up data of an open system I / O subsystem from a mainframe that is not directly connected to the I / O subsystem.

  Another object of the present invention is to enable access from the main frame to a storage device of an I / O subsystem for an open system which is not directly connected to the main frame. .

  Still another object of the present invention is to provide a system in which two or more I / O subsystems having different interfaces can be connected to a main frame.

  In order to achieve the above object, the present invention includes a first host computer and one or more external storage devices directly connected to the first host computer via a variable-length recording format interface. A first I / O subsystem, a second host computer, and a second host computer that is directly connected to the second host computer by a fixed-length recording format interface and includes one or more external storage devices. A second I / O subsystem, and a communication mechanism for connecting the first I / O subsystem and the second I / O subsystem, wherein the first I / O subsystem Is the device address of the external storage device, information indicating whether the device address is assigned to the external storage device of the first or second I / O subsystem, and the information of the second I / O subsystem. External memory A table for storing the device address of the external storage device in the second I / O subsystem when assigned to the external storage device, and an external storage to be read / written from the first host computer. When a read / write request including a device address and according to the variable-length recording format interface is received, the external storage device address included in the read / write request is referred to by referring to the table. If the device address in the storage device is not assigned to an external storage device included in the first I / O subsystem but is assigned to an external storage device included in the second I / O subsystem, Means for deciding to send said read / write request according to a variable length recording format interface to said second I / O subsystem; Converting the read / write request according to the variable length recording format interface determined to be sent to the O subsystem into the read / write request according to the fixed length interface; A means for sending to the second I / O subsystem is provided.

  A first host computer; and a first I / O subsystem directly connected to the first host computer via a variable-length recording format interface and including one or more external storage devices. A backup system connected to the first host computer; a second host computer; and one or more backup systems directly connected to the second host computer via a fixed-length recording format interface. A second I / O subsystem including an external storage device, and a communication mechanism that connects the first I / O subsystem and the second I / O subsystem. The first host computer includes, for the first I / O subsystem, an address of an external storage device from which data is to be read, and follows the variable length recording format interface. Means for issuing a read request and backing up data received from the first I / O subsystem to the backup system, wherein the first I / O subsystem has an external storage The device address of the device, information indicating whether the device address is assigned to the external storage device of the first or second I / O subsystem, and the external storage device of the second I / O subsystem. A table for storing a device address of the external storage device in the second I / O subsystem when allocated, an external storage device address to be read from the first host computer, and When receiving a read request according to the variable length recording format interface, the external storage device address included in the read request is referred to by referring to the table. If the device address in the storage device is not assigned to an external storage device included in the first I / O subsystem but is assigned to an external storage device included in the second I / O subsystem, Means for deciding to send the read request according to the variable-length recording format interface to the second I / O subsystem, and the variable means for deciding to send to the second I / O subsystem The read request according to the long recording format interface is converted into a read request according to the fixed length interface, and the read request is sent to the second I / O subsystem. Means are provided for sending data received from the system to the first host computer.

  A first host computer; and a first I / O subsystem directly connected to the first host computer via a variable-length recording format interface and including one or more external storage devices. A backup system connected to the first host computer; a second host computer; and one or more backup systems directly connected to the second host computer via a fixed-length recording format interface. A second I / O subsystem including an external storage device, and a communication mechanism that connects the first I / O subsystem and the second I / O subsystem. One host computer includes an address of an external storage device to which data is to be written to the first I / O subsystem, and follows the variable length recording format interface. Means for issuing a write request and sending data read from the backup system to the first I / O subsystem, wherein the first I / O subsystem has a device address of an external storage device And information indicating whether the device address is assigned to the external storage device of the first or second I / O subsystem, and is assigned to the external storage device of the second I / O subsystem. A table for storing a device address in the second I / O subsystem of the external storage device, an external storage device address to be written from the first host computer, and the variable length When a write request according to the recording format interface is received, the device address in the external storage device address included in the write request is referred to by referring to the table. If the storage is not allocated to an external storage device included in the first I / O subsystem, but is allocated to an external storage device included in the second I / O subsystem, Means for deciding to send the write request according to a format interface to the second I / O subsystem, and the variable length recording format deciding to send to the second I / O subsystem Converting the write request according to the interface into a write request according to the fixed-length interface, sending the write request to the second I / O subsystem, and receiving the data from the first host computer; To the second I / O subsystem.

  Also, a first I / O subsystem including one or more external storage devices and a second I / O subsystem connected to the first I / O subsystem and including one or more external storage devices And a composite I / O system connected to a host computer, wherein the first I / O subsystem includes a device address of an external storage device and a device address corresponding to the first or second I / O device. Information indicating which of the external storage devices of the O subsystem is assigned, and a second I / O sub-device of the external storage device when assigned to the external storage device of the second I / O subsystem. When a read / write request specifying an external storage device address to be read / written is received from the host computer, a table for storing the device addresses in the system and the table are referred to. A device address in the designated external storage device address is not assigned to an external storage device included in the first I / O subsystem, and the external storage device is included in the second I / O subsystem. When assigned to a device, the apparatus has means for sending the read / write request to the second I / O subsystem.

A first I / O subsystem having a variable length recording format interface and including one or more external storage devices; and a first I / O subsystem having a fixed length recording format interface and including one or more external storage devices. And a communication mechanism for connecting the first I / O subsystem and the second I / O subsystem, and a composite I / O system connected to a host computer. The first I / O subsystem includes a device address of an external storage device, and information indicating whether the device address is allocated to the external storage device of the first or second I / O subsystem. A table for storing a device address of the external storage device in the second I / O subsystem when assigned to an external storage device of the second I / O subsystem; When a read / write request including an external storage device address to be read / written and according to the variable-length recording format interface is received from a computer, referring to the table, The device address in the external storage device address included in the read / write request is not allocated to the external storage device included in the first I / O subsystem, and the second I / O subsystem Means for deciding to send the read / write request according to the variable-length recording format interface to the second I / O subsystem, if the read / write request is allocated to an external storage device included in the second I / O subsystem. And transmitting the read / write request according to the variable length recording format interface determined to be sent to the second I / O subsystem to the fixed length interface. Therefore the re - converted into read / write request, and to have a means for sending to said second I / O subsystem.

  According to the present invention, data can be backed up between I / O subsystems having different access interfaces.

  As a result, the data of the open I / O subsystem can be backed up to the mainframe I / O subsystem.

  Also, since the main frame backup mechanism includes a large capacity, high performance, and highly reliable MT library system, data of the open system I / O subsystem is backed up to a high performance, highly reliable mainframe. In the mechanism, it can be backed up.

  In addition, different I / O subsystems can be connected to the mainframe.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of a computer system to which the present invention is applied.

  The processing system A100 includes a mainframe 101, a channel interface A102, a channel interface B103, a magnetic tape (MT) controller 106, a magnetic tape library controller 130, a magnetic tape library 107, a disk controller A104, a disk device group A105, and a service processor. 109.

  The mainframe 101 accesses the disk controller A104 via a channel interface B103 that follows a variable length record format called a count key data format.

  Here, the count key data format is a record format in which a record as a unit of read / write is composed of three fields called a count section, a key section, and a data section. .

  The count section stores a record identifier, the key section stores key information for accessing the record, and the data section stores data used by the application program. You.

  Hereinafter, the magnetic tape (MT) control device 106, the magnetic tape library control device 130, and the magnetic tape library 107 are collectively referred to as an MT library system 116.

  The storage layers connected via the channel interface include not only magnetic tapes but also optical disks and the like. Hereinafter, a case where the MT library system 116 is connected will be described as an example.

  The disk control device A 104 includes its own control device connection disk information 314 and other control device connection disk information 315.

  The own control device connection disk information 314 and the other control device connection disk information 315 are information provided to enable access to a disk device of an I / O subsystem that is not directly connected from the main frame. The details will be described later.

  The processing system B110 includes an open system host 111, a SCSI interface (Small Computer System Interface) 112, a disk control device B113, a disk device group B114, and a service processor B115.

  The open host 111 accesses the disk controller B 113 via a SCSI interface 112 in which a record as a unit of read / write has a fixed length.

  The disk controller A 104 and the disk controller B 113 are connected by a communication path 108. The communication path 108 may be, for example, a SCSI cable b117.

  Hereinafter, the count key data format is called a CKD format, and the fixed-length block format is called an FBA (Fixed Block Architecture) format.

  Hereinafter, a record in the CKD format is called a CKD record, and a record in the FBA format is called an FBA record.

  FIG. 2 is a diagram showing another example of a computer system to which the present invention is applied. In the I / O subsystem for one main frame, the I / O subsystem for two or more open systems is used. Is connected.

  In the processing system X120, the interface between the open system host X121 and the disk control device X123 is connected by a Fiber Channel interface 122. The Fiber Channel interface 122 is an optical cable and can increase the connection distance between the host and the control device.

  However, a SCSI-based Fiber Channel interface is often used between the host and the control device.

  Further, the disk controller X123 and the disk controller B113 may also be connected by an interface such as a Fiber Channel interface X126.

  The data backup in the configuration of FIG. 2 is an extension of the data backup in the configuration of FIG.

  The basic operation of each device is as follows. The mainframe 101, the open hosts 111 and 121 communicate with the magnetic tape library 107 as an external storage device, the disk device group A 105, the disk device group B 114, Access the device group X124.

  The process of the mainframe 101 is under the control of any operating system that supports a channel interface, for example, VOS3 (Virtual-storage Operating System 3) of Hitachi, Ltd., and the process of the open host supports the SCSI interface. Under the control of any operating system (for example, UNIX UNIX is a registered trademark of X / Open in the United States and other countries), the data stored externally through each interface is controlled. Establish a route for

  FIG. 3 is a diagram illustrating a configuration of the disk control device A104.

  The disk control device A 104 includes an MPU 302, a memory device 301, a host data transfer device 303, a disk cache device 304, a data transfer device 305 between I / O subsystems, which executes a control system process 307 of the present disk control device. 306, a bus 308 connecting these devices.

  The control system process 307 operates in a multitask or multiprocessor environment.

  The memory device 301 includes various micro programs 312 and various data 313.

  In particular, in the case of the disk control device A 104, the own control device connection disk information 314 and the other control device connection disk information 315 are stored as described in FIG.

  The disk control device B113 and the disk control device X123 have the same configuration, and therefore will not be described.

  However, in the case of the disk control device B113 and the disk control device X123, it is not necessary to include the own control device connection disk information 314 and the other control device connection disk information 315.

  The own control device connection disk information 314 indicates the connection relation of the control devices and the like stored in the memory device 301 of the disk control device A 104. The own control device connection disk information 314 is information that exists corresponding to the disk device.

  FIG. 4 shows the self-control device connection disk information 314.

  The device address 400 is an identifier for the host computer such as the main frame 101 to identify a disk to be read / written, and is issued by the host computer such as the main frame 101. This information is also included in the read / write request.

  The own control device connection information 401 is information indicating whether the disk device corresponding to the control device connection disk information 314 is actually connected to the control device.

  The other control device connection pointer 402 indicates whether the control device connection disk information 314 is allocated to a disk device connected to another control device.

  If assigned, the pointer points to the corresponding other control device connection disk information 315. If not, the pointer is a null value.

  Therefore, when the other control device connection pointer 402 is valid (when the device address 400 is allocated to a disk device connected to another control device), the own control device connection information 401 is in a state where it is not allocated. It is in.

  When the other control device connection pointer 402 is invalid (when the device address 400 is not allocated to a disk device connected to another control device), the own control device connection information 401 is allocated. It may indicate no state.

  That is, there may be a state where the device address 400 is not assigned to the disk device connected to the own control device, or is not assigned to the disk device connected to another control device.

  The attribute 403 is device-specific information such as the interface, function, data format type, and block length of the corresponding disk device.

  The other control device connection disk information 315 illustrated in FIG. 5 is information corresponding to a disk device that is not directly connected to the disk control device A104.

  The other control device connection disk information 315 is pointed from any of the own control device connection disk information 314.

  The connection control device address 500 stores the address of the control device to which the disk device corresponding to the other control device connection disk information 315 is connected. In this embodiment, the disk control device B113 is stored.

  The disk address 501 indicates an address assigned to the corresponding disk device in the control device actually connected.

  The own control device connection disk information 314 and the other control device connection disk information 315 are set by the service processor 109, for example.

  In the present embodiment, as shown in FIG. 6, the main frame 101 uses the information of the own control device connection disk information 314 and the other control device connection disk information 315 shown in FIGS. The disk device group B114 (disk C, disk D) connected via the control device B113 is also recognized as being connected to the disk control device A104.

  This is because the disk controller A104 assigns the addresses of the disk units that are free in the disk controller A104 to the disk units of the open I / O subsystem.

  Hereinafter, the contents of the backup processing will be described with reference to FIGS. 1, 7, and 8. FIG.

  More specifically, in FIG. 1, the data of the disk unit group B114 of the open system of the processing system B is backed up to the MT library system 116 via the disk controller A104 of the processing system A and the mainframe 101.

  Conversely, the data backed up in the MT library system 116 is restored to the disk group B114 of the open system of the processing system B via the mainframe 101 of the processing system A and the disk controller A104.

The above-mentioned backup and restore are executed in accordance with an instruction from the mainframe 101. First, data of the disk unit B114 of the open system of the processing system B is transferred to the MT via the disk controller A104 of the processing system A and the mainframe 101. A case where backup is performed in the library system 116 will be described.

  As described above, in the main frame 101, it is recognized that the disk device group B114 (disk C and disk D) is also connected to the disk device A104.

  Therefore, the operation of the main frame 101 will not be described in particular because it merely issues a read request to the disk controller A 104 and backs up the received data to the MT library system 116.

  When performing backup in the MT library system 116, the mainframe 101 issues a read request to the disk controller A104. Upon receiving the read request from the mainframe 101, the disk controller A104 executes the processing according to the flowchart of FIG.

  First, in step 700, the corresponding self-control device connection disk information 314 is found from the address of the disk device specified in the read request.

  In step 701, it is checked whether the specified disk device is connected to the disk controller A104.

  If it is connected to the disk control device A 104, the corresponding data is read from the disk device in step 702.

  If it is not connected to the disk controller A104, it is checked in step 703 whether the specified disk device is connected to another disk controller (disk controller B113). That is, it is checked whether the other control device connection pointer 402 has a null value.

  As a result of the check, if the value is null and the connection is not established, an error report is made in step 704.

  The operation particularly related to the present invention is the operation after step 705 executed when the designated disk device is connected to another disk control device (disk control device B113).

  First, as a result of the check, if the value is not a null value and it is connected, in step 705, based on the value of the other control device connection pointer 402, the other control device connection disk corresponding to the designated disk device Information 315, and based on the found other control device connection disk information 315, the address of the disk control device (disk control device B113) to which the specified disk device is actually connected, the disk connected to the disk control device. The address of the disk device within the device group B is obtained.

  Next, in step 706, the address of the data to be read received in the read request is converted into the format of the disk device connected to the disk controller B113.

  In a read / write request from the mainframe 101, the address of data to be read / written is usually specified by a cylinder number, a head number, and a record number in accordance with a normal CKD format.

  Hereinafter, a record address represented by a cylinder number, a head number, and a record number is referred to as CCHHR.

  On the other hand, the disk device connected to the disk control device B113 has an access interface specified by LBA (Logical Block Address) according to the FBA format.

  Therefore, in step 706, the access address of the data to be read is converted from the CKD format to the FBA format.

The conversion formula is, for example,
LBA = (CC * number of heads + HH) * track length + record number * record length.

  In step 707, a request is issued to the disk controller B113 to read data from the area calculated in step 706 of the relevant disk device.

  Step 708 waits for the requested data from the disk controller B113.

  In step 709, the data received from the disk controller B113 is sent to the main frame 101, and the process is completed.

  The disk control unit 113B only reads out the data requested from the disk control unit A104 from the corresponding disk unit and sends it to the disk control unit A104.

  Next, a case where data backed up in the MT library system 116 is restored to the disk group B114 of the open system of the processing system B via the disk controller A104 of the processing system A and the mainframe 101 will be described.

  As described above, in the main frame 101, it is recognized that the disk control device group B113 (disk C and disk D) is also connected to the disk device A104.

  Therefore, the operation of the main frame 101 will not be described in particular because it merely issues a write request to the disk controller A104 to write the data read from the MT library system 116.

  Upon receiving a write request from the mainframe 101, the disk controller A104 executes processing according to the flowchart of FIG.

  In the processing flow of FIG. 8, the processing in steps 800 to 801 and steps 803 to 806 is the same as the processing in steps 700 to 701 and steps 703 to 706 in FIG. Step 802 is a normal write process because the request from the mainframe 101 is a write request.

  Hereinafter, only the portions different from FIG. 7 will be described.

  In step 807, a request to write data to the area calculated in step 807 of the relevant disk device is issued to the disk controller B113.

  Next, in step 808, write data is received from the main frame 1101 and sent to the disk controller B113.

  Next, in step 809, the process waits for a write request completion report from the disk controller B113, and upon receiving the completion report, sends a completion report to the main frame 101 and completes the process.

  The controller 113B only reads out the data requested from the disk controller A104 from the corresponding disk device and sends it to the disk controller A104, so that no particular processing flow is described.

  As described above, the system in which the data of the disk unit group B114 of the open system of the processing system B is backed up by the processing system A has been described. A composite I / O system in which two I / O subsystems having different interfaces are connected to a mainframe may be configured. In this case, three or more I / O subsystems may be connected.

FIG. 1 is a diagram illustrating an example of an outline of a system according to an embodiment. It is a figure showing other examples of the outline of the system of an example. FIG. 2 is a diagram illustrating a configuration of a disk control device. FIG. 4 is a diagram showing a configuration of self-control device connection disk information. FIG. 4 is a diagram showing a configuration of another control device connection disk information. FIG. 4 is a diagram showing a connection relationship of the disk devices as viewed from the main frame. FIG. 9 is a diagram showing an example of a processing flow of a disk control device A when backing up data of an open I / O subsystem to an MT library system of a mainframe. FIG. 11 is a diagram showing an example of a processing flow of a disk control device A when restoring data from an MT library system of a mainframe to an open I / O subsystem.

Explanation of reference numerals

101 Main frame 102, 103, 122 Channel interface 111, 121 Open host 112 SCSI interface 104, 113, 123 Disk controller 105, 114, 124 Disk device group 106 Magnetic tape controller 107 Magnetic tape library 108 Communication path 109, 115 , 125 service processor 116 MT library system 130 library controller 301 memory device 302 MPU
303 Host data transfer device 304 Disk cache device 305 Data transfer device between I / O subsystems 306 Disk transfer device 307 Control system process 312 Micro program 313 Data 314 Self-control device connection disk information 315 Other control device connection disk information

Claims (5)

A first host computer, a first I / O subsystem directly connected to the first host computer via a variable length recording format interface, and including one or more external storage devices;
A second host computer, a second I / O subsystem directly connected to the second host computer via a fixed-length recording format interface, and including one or more external storage devices;
A compound computer system including a communication mechanism for connecting the first I / O subsystem and the second I / O subsystem,
The first I / O subsystem comprises:
The device address of the external storage device, information indicating whether the device address is assigned to the external storage device of the first or second I / O subsystem, and the external storage of the second I / O subsystem A table for storing a device address in the second I / O subsystem of the external storage device when assigned to the device;
When receiving a read / write request from the first host computer, the read / write request including an external storage device address to be read / written and according to the variable length recording format interface, In the case where a device address in an external storage device address included in the read / write request is assigned to an external storage device included in the second I / O subsystem, the variable length Means for deciding to send a read / write request to the second I / O subsystem based on the read / write request according to a recording format interface;
The read / write request according to the variable-length recording format interface determined to be sent to the second I / O subsystem is converted into a read / write request according to the fixed-length interface. And a means for transmitting the data to the second I / O subsystem. A first host computer, a first I / O subsystem directly connected to the first host computer via a variable length recording format interface, and including one or more external storage devices;
A backup system connected to the first host computer;
A second host computer, a second I / O subsystem directly connected to the second host computer via a fixed-length recording format interface, and including one or more external storage devices;
A compound computer system including a communication mechanism for connecting the first I / O subsystem and the second I / O subsystem,
The first host computer includes, for the first I / O subsystem, an address of an external storage device from which data is to be read, and transmits the data to the variable length recording format interface. Means for issuing a read request in accordance with the data and backing up data received from the first I / O subsystem to the backup system;
The first I / O subsystem includes a device address of an external storage device, information indicating whether the device address is assigned to the external storage device of the first or second I / O subsystem, A table for storing a device address in the second I / O subsystem of the external storage device when allocated to the external storage device of the second I / O subsystem;
When a read request including an external storage device address to be read and according to the variable length recording format interface is received from the first host computer, the read request is referred to by referring to the table. Is assigned to the external storage device included in the second I / O subsystem, the read request according to the variable length recording format interface is Means for deciding to send to the second I / O subsystem;
Converting the read request according to the variable-length recording format interface determined to be sent to the second I / O subsystem into a read request according to the fixed-length interface; And a means for sending data received from the second I / O subsystem to the first host computer. A first host computer, a first I / O subsystem directly connected to the first host computer via a variable length recording format interface, and including one or more external storage devices;
A backup system connected to the first host computer;
A second host computer, a second I / O subsystem directly connected to the second host computer via a fixed-length recording format interface, and including one or more external storage devices;
A compound computer system including a communication mechanism for connecting the first I / O subsystem and the second I / O subsystem,
The first host computer includes an address of an external storage device to which data is to be written to the first I / O subsystem, and follows the variable length recording format interface. Means for issuing a write request and sending data read from the backup system to the first I / O subsystem;
The first I / O subsystem comprises:
The device address of the external storage device, information indicating whether the device address is assigned to the external storage device of the first or second I / O subsystem, and the external storage of the second I / O subsystem A table for storing a device address in the second I / O subsystem of the external storage device when assigned to the device;
When a write request including an external storage device address to be written and according to the variable length recording format interface is received from the first host computer, the write request is referred to by referring to the table. Is assigned to an external storage device included in the second I / O subsystem, the write request according to the variable-length recording format interface is sent to the external storage device. Means for deciding to send to the second I / O subsystem;
Converting the write request according to the variable-length recording format interface determined to be sent to the second I / O subsystem into a write request according to the fixed-length interface; And a means for sending the data received from the first host computer to the second I / O subsystem. A first I / O subsystem including one or more external storage devices;
A second I / O subsystem connected to the first I / O subsystem and including one or more external storage devices;
A composite I / O system connected to a host computer,
The first I / O subsystem comprises:
The device address of the external storage device, information indicating whether the device address is assigned to the external storage device of the first or second I / O subsystem, and the external storage of the second I / O subsystem A table for storing a device address in the second I / O subsystem of the external storage device when assigned to the device;
When a read / write request specifying an external storage device address to be read / written is received from the host computer, the device address in the specified external storage device address is referred to by referring to the table. Has a means for sending the read / write request to the second I / O subsystem when the read / write request is allocated to an external storage device included in the second I / O subsystem. Complex I / O system. A first I / O subsystem having a variable length recording format interface and including one or more external storage devices;
A second I / O subsystem having a fixed-length recording format interface and including one or more external storage devices;
A communication mechanism for connecting the first I / O subsystem and the second I / O subsystem,
A composite I / O system connected to a host computer,
The first I / O subsystem comprises:
The device address of the external storage device, information indicating whether the device address is assigned to the external storage device of the first or second I / O subsystem, and the external storage of the second I / O subsystem A table for storing a device address in the second I / O subsystem of the external storage device when assigned to the device;
When a read / write request including the address of an external storage device to be read / written and according to the variable length recording format interface is received from the host computer, the table is referred to. When a device address in the external storage device address included in the read / write request is assigned to an external storage device included in the second I / O subsystem, the variable length recording format interface Means for deciding to send said read / write request according to a face to said second I / O subsystem;
The read / write request according to the variable-length recording format interface determined to be sent to the second I / O subsystem is converted into a read / write request according to the fixed-length interface. A composite I / O system, comprising: means for converting the data into the data and sending the converted data to the second I / O subsystem.

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