JPH08241262A - External storage extension system - Google Patents

Abstract

PURPOSE: To provide the access system of shared data between plural host computers by connecting an external storage device to a second controller control part via the same interface as a first interface. CONSTITUTION: The CPU part 31 of a host computer 10 starts an SCSI controller 33 via an IO bus 32 for inputting the data from an external storage device 29. The SCSI controller 33 receives the instruction of the CPU part 31, converts the instruction into a pertinent SCSI command and delivers the command to an SCSI bus by defining a host side controller 35 as a target. Next, instructions are successively converted into packets and the packets are transmitted to an external storage device side controller 45 via a packet exchange 42. The external storage device side controller 45 stores the received packet data in the data buffer prepared corresponding to each host computer, next takes out the SCSI command and SCSI ID number from the data buffer and instructs an SCSI controller 47 via an IO bus 46.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resource management system for a computer system, and more particularly to a control system suitable for sharing data in an external storage device among a plurality of computers.

[0002]

2. Description of the Related Art FIG.
It is a block diagram of the conventional external storage device shown in 0424. In the figure, 10, 11 and 12 are host computer groups that share this external storage device, and 13, 14 and 15 are OSs (operating systems) independently mounted in these host computer groups. Further, channels 16, 17, and 18 are connected to the respective host computer groups, and the external storage controller 1 is connected via the respective channels 16, 17, and 18.
The magnetic disk device 21 connected to the CPU 9 is accessed.

Access to the data on the magnetic disk device 21 shared by the host computer group (10 to 12) can be executed only by one host computer at one time. Therefore, the user has to issue an exclusive control request to the OS in order to obtain the right to use the magnetic disk device. The OS that has received the exclusive control request receives the CC corresponding to the first data transfer input / output request after the exclusive control request.
A RESERVE command for exclusive control is chained at the beginning of W (command control word). CCW
Is transmitted to the external storage controller 19 through the channel. Here, one format of CCW is shown in FIG. The beginning of the CCW shows the command code. In FIG. 8, the RESERVE command is X'24 'and the RELEASE command is X'4.
4 ', UNCONDITIONAL-RESERVE is indicated by X'54'. Here, the RESERVE command is for securing the lock of the magnetic disk device by using the exclusive control identifier in the external storage control device 19 as a key and prohibiting the use from other host computer groups. R
The ELEASE command releases the lock with the exclusive control identifier as the key, and UNCONDITIONAL-RESERVE forcibly releases the lock with the other host computer group with the exclusive control identifier as the key, and controls the own host computer exclusively. This is a command to secure a lock with an identifier as a key. The external storage controller 19 operates as follows. (1) The external storage control device 19 receiving the RESERVE command refers to the exclusive control identifier management table stored in the control memory 20 in the external storage control device, using the exclusive control identifier specified in the RESERVE command as a key. . (2) As a result of the reference, if the exclusive control identifier is already registered in the exclusive control identifier management table, the host computer that registered the exclusive control identifier is read out and the host computer of the RESERVE command issued this time is matched. It is determined whether to do. (3) If the result of determination is that the data set is not locked by another host computer, it is newly registered in the exclusive control identifier management table. After this, the host computer accesses the data on the magnetic disk device. (4) If the lock has already been secured by another host computer, the fact that the magnetic disk device is in use is reported to the requesting host computer, and the process ends without executing data access to the disk device. Here, if the other host computer system goes down with the exclusive control identifier registered in the management table, the corresponding data set becomes inaccessible from the other host computer. For this reason, the other host computer is RELEASE
Command and UNCONDITIONAL-RESERV
The E command is issued to forcibly delete the exclusive control identifier, or the exclusive control identifier of the host computer is registered to prevent the data access to the magnetic disk device from being disabled. Here, the RELEASE command deletes the corresponding exclusive control identifier from the exclusive control identifier management table and executes UNCONDITIONAL
-RESERVE is a command for forcibly registering the corresponding exclusive control identifier in the exclusive control identifier management table.

[0004]

Since the conventional external storage device has been operated as described above, since the external storage device can be used by only one host computer at a certain point of time, the access of each host computer is possible. The request is serialized. For this reason, when a certain host computer transfers a large amount of data, the access of the subsequent host computer is waited for, and it cannot be predicted how much the already running host computer will occupy the external storage control device. However, there is a problem that it causes an I / O timeout error. In addition, if the host computer that issued the RESERVE command goes down, the RESER
The external storage device that has been VE becomes unusable from the other host computer, and in order to recover this state, the RELEASE command and UNCONDITIONAL-RESERVE command are issued to change the exclusive control identifier to enable access from the other host computer. I was there. However, in order to do this, it is necessary to communicate between each host computer to detect the host computer that caused the system down.As a management method, the host computer that is higher in the system judges and However, in a system having a distributed configuration, there is no particular host computer at a higher level, which makes it difficult to issue this command itself. Further, the interface between the host computer and the external storage device requires special hardware and procedures for data sharing as described above. Therefore, new development of dedicated hardware and software is required,
As a result, the application software has a structure that depends on the hardware configuration, which makes it difficult to standardize and cost reduction.

The present invention has been made in order to solve the above problems. In order to enable efficient use of the external storage device, the external storage device is shared by a plurality of host computer groups. Even if there is, the maximum waiting time is guaranteed for the data transfer request from one host computer,
Another object of the present invention is to provide an access method for shared data between a plurality of host computers using a low-cost hardware device having a standard interface method.

[0006]

According to a first aspect of the present invention, there is provided an external storage expansion method, wherein a host computer executes a user program in an external storage expansion method in which an external storage means is shared among a plurality of host computers. , An external exchange via a first controller control unit connected to the arithmetic unit via a first interface, and a second interface connected to the first controller control unit and different from the first interface. The external exchange is provided with a first control unit for performing packet data transfer, and the external exchange sends commands from a plurality of host computers to corresponding external storage means based on the packet data or the processing results in the external storage means to the host computer. The external storage means performs the processing for relaying data to the host computer via the external exchange. The external storage device includes a second control unit that analyzes a packet received in the buffer and issues a command to a second controller control unit connected through the same interface as the first interface. The controller is connected to the controller via the same interface as the first interface.
According to a second aspect of the present invention, in the external storage expansion method according to the first aspect, the first control unit divides the transmission / reception command received from the first controller control unit into a plurality of blocks, each of which is packetized and then transmitted. The second control unit is configured to execute the data transfer requests from a plurality of host computers in parallel in packet units by executing the packet data that has been divided and transmitted as independent commands. According to a third aspect of the present invention, in the external storage expansion method according to the first aspect, the second control unit receives all the packet data constituting the write data from the host computer for the data write processing to the external storage device. At the point of time, the host computer is notified of the completion of processing, and in the process of reading data from the external storage device, when all the data is taken in via the second controller control unit, the second controller control unit is set to another host. It is also possible to switch to data transfer processing for a computer. According to a fourth aspect of the present invention, in the external storage expansion method according to the first aspect, the second control unit is provided with a data buffer shared by unspecified host computers in addition to the data buffer provided for each host computer. In the state where all the shared data buffers are in use, the data buffer provided for the above computer is used. According to a fifth aspect of the present invention, in the external storage expansion method according to the first aspect, an external storage device having a function of simultaneously receiving a plurality of commands and appropriately changing the execution order of the commands internally to optimize the operation is connected. In such a case, the second control unit limits the number of commands continuously issued to the second controller control unit to a certain number or less in advance, and after the execution of the command group issued earlier is completed, The command group of is sent. Sixth
In the external storage expansion method according to the first to fifth inventions, the first interface is configured as a SCSI interface.

[0007]

In the external storage expansion system according to the present invention, the first control unit receives the command issued from the arithmetic unit on the host computer via the first controller control unit, and then packetizes it to form the external exchange. The second control unit, which is sent to the external storage means, analyzes the packet received in the data buffer provided for the host computer via the external exchange and controls the external storage device. Issues a command to the controller controller. A second invention is the external storage expansion method according to the first invention,
The first control unit divides the received command into a plurality of blocks, packetizes and transmits the packets, and the second control unit executes the received fragmented packet data as an independent command in packet units. According to a third aspect of the present invention, in the external storage expansion method according to the first aspect, the second control unit receives all packet data corresponding to write data from the host computer in response to a WRITE operation to the disk device. At that time, the host computer is notified of the completion of processing, and when the data is read from the external storage device, when the data is completely read from the disk device, the second controller control unit sends the data to another host computer. Control so that it is also directed to transfer processing. A fourth invention is the external storage expansion method according to the first invention, wherein in addition to the data buffer provided in the second control unit for each host computer, a data buffer shared by unspecified host computers is provided. And the buffer control is performed by using the data buffer provided for the computer in a state where all the shared data buffers are used. The fifth invention is the first invention.
In the external storage expansion method according to the invention described above, in the case where an external storage device having a function of receiving a plurality of commands at the same time and internally changing the execution order of the commands to optimize the operation is connected, The control unit limits the number of commands continuously issued to the second controller control unit to a fixed number or less in advance, and sends the next command group after the execution of all the previously issued command groups is completed. Performs command transmission processing. Further, the sixth invention is
In the external storage expansion method according to the first to fifth inventions, the first interface is realized by a SCSI interface.

[0008]

【Example】

Example 1. A first embodiment of the present invention will be described below with reference to FIG.
It will be described with reference to FIG. FIG. 1 is an overall configuration diagram showing a sharing system of an external storage device. In FIG.
Reference numeral 1 is a host computer using an external storage device, 29 is an external storage device, 31 and 36 are CPU units of the respective host computers, 3
2 and 37 are IO buses for controlling peripheral devices, and 33 and 38
Is a standard off-the-shelf SCS for controlling SCSI devices
It is an I controller and usually has one SCSI-ID number. 34 and 39 are SCSI buses, and 35 and 40 are S
A host computer side control device for analyzing control information acquired via the CSI bus and converting it into packet data, 41,
43 is a signal cable for transmitting packet data to the next stage, 4
2 is a packet switch for switching packet data to an appropriate connection point. 44 is a signal cable for transferring data with the host computer selected by the packet switch 42, 4
Reference numeral 5 denotes a control device on the side of the external storage device that performs data transfer with the host computers 10 and 11, each of which has a data buffer for storing a packet corresponding to the host computer, analyzes the contents of the packet, and sends the data from which host computer. It recognizes whether it is a packet and responds to it. Here, the external storage device side control device 45 executes one packet as one independent command composed of a plurality of packets. 46 is an IO bus in the external storage device, 47 is a commercially available standard SCSI controller that performs data transfer with the external storage device side control device via the IO bus 46, 48 is a SCSI for connecting the SCSI controller 47 and the storage device Bus, 4
Reference numerals 9 and 50 denote storage devices for storing information of the host computers 10 and 11, which usually correspond to magnetic disk devices.
The CSI-ID numbers are set as "2" and "3". In this way, the SCSI controllers 33, 38, the host side control devices 35, 40, the signal cables 41, 43, 4
4, packet switch 42, external storage device side control device 45
The external memory expansion mechanism 51 is formed by. In addition, the host computer side control devices 35 and 40, the packet switch 42,
The external storage device side control device 45 has a unique address for data transfer.

FIG. 2 is a diagram showing the format of a SCSI command issued by the SCSI controller 33 to the external storage expansion device 5, and is an example of a command having a length of 10 bytes. The command is issued from a control device called an initiator and transmitted to a device called a target. Usually, the initiator is a SCSI controller, and the target is a storage device such as a magnetic disk or a CD-ROM. In this embodiment, the target is the host computer 10,
11 corresponds to the host-side control devices 35 and 40, and the external storage device 29 corresponds to the storage devices 49 and 50. In this figure, the left column shows the byte number indicating the order in which the instructions are sent, and the right column shows the field name of the byte data. The SCSI command sends byte numbers 0, 1, 2, 3. ． ． Are sent in the order of. Byte number 0 is OPERATION-CO
The type of operation is indicated by DE. For example, when reading from the magnetic disk device, "X'28 '" which means "READ-EXTEND" is set. In the case of writing, "X'2" which means "WRITE EXTEND"
A '"is set. The byte number 1 is a field for expanding the unit number, and is usually "X'00 '" on the magnetic disk. Byte numbers 2 to 5 are LOGI
CAL-BLOCK-ADDRESS indicates a logical address in the target. Byte number 2 is the highest byte and byte number 5 is the lowest value byte. Byte number 6 is a reserved byte according to the SCSI standard and "X'00 '" is set. Byte numbers 7 and 8 are TRANSFER-L
The size of the data transferred by ENGTH is shown. Byte number 7 is the highest value and byte number 8 is the lowest value. In this embodiment, the data size of "1" is 1,024 bytes, and the data of the data size of "1" will be referred to as one block data, and the description will be given with reference to this. Finally, byte number 9 is CONTROL-BYT
Although an instruction for the operation of the device is given with E, this is not used in this embodiment, so "X'00 '" is set.

FIG. 3 shows a SCSI command READ-E.
It is an example of XTEND. In this example, the logical address "X'8
It is instructed to transfer the data of the "X'8000 '" block (bytes 7 and 8) starting from "0000000'" (byte numbers 2 to 5) to the initiator.

In FIG. 4, the host-side control devices 35 and 40 execute one SCSI command shown in FIG. 3 with a data transfer size of 64 blocks (X'0040 ') and a transfer destination start logical address (byte number 2). Through 5) "X'8000
0000 ′ ”indicates that the transfer logical address is decomposed into a plurality of SCSI commands that are incremented by the data transfer size (X′0040 ′) each time the command is issued.

FIG. 5 illustrates the format of packets used by the host side control devices 35, 40, the packet switch 42, and the external storage device side control device 45. The packet switch analyzes the receiving side address of the packet and relays this packet to the receiving device side. The packet is divided into four parts. The first part shows the address of the sender, the second shows the address of the receiver, the third shows the command / status that conveys the meaning of the packet and the status of the sender, and finally the input / output transfer data accompanying the execution of the SCSI command. As a result, data with a maximum length of 64 KB is attached. 64K here
B length data is 64 blocks (1 block length is 1, 0
24 bytes) of data, and the data contents include the SCSI commands shown in FIGS. 2 and 3. The host-side control device and the external storage device-side control device perform a series of processing relating to packet transmission and reception. Also,
The packet switch does not perform any processing in accordance with the contents of the packet except for the notification when the connection abnormality occurs, and only analyzes the address on the receiving device side of the packet and relays the packet to the receiving side. Normally, packet transmission is executed by the host-side control device, and reception operation is performed by the external storage device-side control device. The external storage device-side control device analyzes the content of the received packet, and executes control and data input / output processing for the SCSI controller and SCSI device according to the content. As a result of the execution, when it is necessary to return data or status information to the host-side control device, the external storage device-side control device generates a packet and sends it to the host-side control device.

Next, regarding the operation, the host computer 10 executes S
From the logical address "X'80000000 '" to "X'80" of the magnetic disk device 49 having the CSI-ID number "2"
The case of reading the data of the “00 ′” block will be described as an example. First, the CPU unit 31 of the host computer 10 activates the SCSI controller 33 via the IO bus 32 for data input from the external storage device 29. Since the SCSI controller 33 is a commercially available standard controller, the CPU section 31 issues a command using the standard software interface. (1) The SCSI controller 33 receives an instruction from the CPU unit 31, converts it into a corresponding SCSI command, and sends it to the SCSI bus with the host-side controller 35 as a target. The SCSI command sent here is the "READ-EXTEND" command in FIG. (2) The host-side controller sends this SCSI command to the "R" in 64 block (X'0040) units as shown in FIG.
"EAD-EXTEND" 512 times, address 64
Change to multiple instructions that repeat while incrementing by (X'0040). (3) Next, these commands are sequentially converted into packets shown in FIG. 5 and transmitted to the external storage device side control device 45 via the packet switch 42. At this time, the SCS is added to the command / status part of the packet generated by the host controller.
Information such as that the I command is transmitted and the SCSI ID number designated by the SCSI controller is set. (4) The external storage device-side control device 45 stores the received packet data in a data buffer prepared for each host computer, then extracts the SCSI command and SCSI ID number from the data buffer and outputs it to the SCSI controller 47 for IO. Instruct via bus 46. Here, since the external storage device-side control device executes the individual instructions packetized by dividing the instruction specified by the host computer into blocks, a series of commands issued from other host computers. Even if the processing of the entire packet for the instruction is not completed, the control can be shifted to the execution of the packet related to the instruction from the computer as long as the data transfer for the currently executed packet is completed. At this time, the execution of the packet corresponding to each host computer is equally performed to each host computer. (5) Next, the SCSI controller 47 uses the SCSI-I
Targeting the magnetic disk device 49 from the D number,
Commands are sent out via the SCSI bus 48. (6) The magnetic disk device 49, which is the target, sends the data at the designated address to the SCSI, which is the initiator.
It is sent to the controller 47. (7) The SCSI controller 47 sends the data to the external storage device-side control device 45 and completes the processing for the packet corresponding to one block. (8) The external storage device-side control device 45 packetizes this data and issues the command to the host-side control device 35.
Forward the response to. (9) The host-side control device extracts data from the received packet and sends it to the SCSI controller 33. (10) The SCSI controller 33 sends data to the CPU section 31. By repeating the above operations (3) to (9) 512 times, all data input from the magnetic disk device 49 of the host computer 10 is completed. The basic operation of the data output process is the same except that the data transfer direction is reversed, and the data input / output process from the host computer 11 is performed in the same manner. Therefore, even if the host computers 10 and 11 perform simultaneous operations, they are executed in the same manner except that the step (4) includes the process of executing the instruction from the other host computer.

According to this embodiment, since the user program interface on the host computer and the controller interface with the controller mounted on the external storage device are realized as the same interface, the homogeneity of the system is guaranteed. A system in which a plurality of host computers share a plurality of external storage devices can be easily constructed and changed. In addition, the input / output instruction issued from the host computer is divided into a plurality of input / output instructions in which the transfer length is suppressed to a certain amount or less, and the divided instructions are executed as independent instructions. Since it is possible to process the instructions in parallel, it is possible to prevent the occupation of a specific host computer for a long time due to a large amount of data transfer and to equalize the services. Further, since the user program interface on the host computer and the controller interface for the control device mounted on the external storage device are realized by the same standard interface, it is not necessary to manufacture special software, and portability is secured. .

Although the packet format is exclusively defined as shown in FIG. 5 in the above embodiment, if the entire packet is regarded as data, standard packet interfaces such as ATM and Fiber channel can be used. Since it can be applied, the type of interface connecting the host computer and the external storage device can be appropriately selected according to the purpose, performance, and price.

Example 2. A second embodiment of the present invention will be described based on FIG. FIG. 6 shows the first embodiment in which two external storage devices 29 are provided and the same numbers are assigned to the same components. 52 here
Is a signal cable for data transfer with the host computer,
53 is an external storage device-side control device, 54 is an IO bus in the external storage device, 55 is a SCSI controller, and 56 is an SC.
SI buses, 57 and 58 are storage devices, and usually correspond to magnetic disk devices. In this embodiment, the external storage device (2
9, 59) are connected to the packet switch 42, and an address for transmitting / receiving a packet to / from the host computer is additionally set. As a result, the host-side control device 35 converts the requests from the host computer into a plurality of SCSI commands as shown in FIG. 4, generates the commands, and then distributes and activates them to the two external storage devices based on the configuration of FIG. Since these two external storage devices operate simultaneously, the data transfer speed can be improved.

Embodiment 3. A third embodiment of the present invention will be described. In this embodiment, instead of sequentially executing the processing from the start of the host computer until the data transfer processing between the magnetic disk device and the host computer is completed, instead of storing the packet in the external storage device side control device. When the data storage process is completed in the data buffer, the next process can be executed. That is, in the case of data output (WRITE), the external storage device-side control device returns a response indicating that the processing is completed when the reception of the packet data from the host computer is completed. When the host computer receives the response indicating the completion of the processing, it judges that all the processing related to the instruction issued to the external storage device is completed, and moves to the next new data processing. After that, the external storage device-side control device transfers data from the data buffer to the magnetic disk device based on its own processing timing. On the other hand, in the case of data input (READ), SCSI
The controller completes the data input process when the corresponding data in the magnetic disk device is stored in the data buffer dedicated to each host of the external storage device side control device. To execute. According to this embodiment, in the data output process, the host computer is notified that the process is completed at the time when the transfer data is stored in the data buffer in the external storage device, and in the data input process, the magnetic disk device transmits the data buffer. Since the data transfer process to another host computer can be executed at the time when the data is read, it is possible to speed up the process of the entire system.

Example 4. A fifth embodiment of the present invention will be described. In the present embodiment, in addition to the packet storage data buffer in the external storage device side control device which was prepared for each host computer, a plurality of shared data buffers not particularly limiting the host computer are prepared. It is the one. In this case, first, the data transfer is performed using the shared data buffer, the shared data buffer is used up, and then the dedicated data buffer for each host computer is used. As a result, the state of buffer full can be avoided in the data transfer to each host computer, so that the transfer process is guaranteed to be continuously executed. In particular, by using together with the third embodiment, in the data output (WRITE operation) processing, higher speed processing can be realized. According to this embodiment, a dedicated data buffer corresponding to the host computer and a data buffer shared by unspecified host computers are provided, and the dedicated buffer is used when all the shared data buffers are in use. Therefore, the continuous execution of the transfer process is guaranteed, and more buffers can be allocated to the host computer that transfers a large amount of data.

Embodiment 5 FIG. A fifth embodiment of the present invention will be described. As shown in the fourth embodiment, in the configuration in which a large number of data buffers are prepared, a plurality of SCSI commands may exist in the external storage device side control device during execution. On the other hand, some magnetic disk devices receive a plurality of commands at the same time (command queuing), and exchange the execution of the commands inside the disk device (reorder) to optimize the operation. When using such a magnetic disk device, the external storage device side control device continuously sends a plurality of commands. As a result of performing the optimum placement processing of multiple commands, access to data at a position significantly distant from the current head position of the magnetic disk device may be relocated at the end of a series of command executions. It is difficult to determine the command execution completion time. In addition, if an error occurs in execution of one command in multiple command groups, the relocated command that follows it may be affected by the error and discarded. The recovery process is difficult because it cannot be confirmed by the storage device side control device. Therefore, the external storage device-side control device determines in advance that the number of commands to be continuously transmitted is, for example, up to 16. When all 16 commands have been executed, the next 16 commands are sent. By doing so, even for a command group optimized inside the magnetic disk device, the maximum execution time required for the entire command group to complete execution can be roughly calculated (the worst value). this is,
Since the data input / output command is issued in units of 64 blocks, the maximum value of the seek time of the head and the worst value of the data transfer can be calculated from the SCSI controller and the magnetic disk specifications. This is because the execution time has been clarified as a specification, and the maximum value of the execution time of the command group can be predicted. According to this embodiment, the number of commands to be continuously output is limited to a predetermined number or less in advance, and the next command group is sent after the execution of the previous command group is completed. Even when the magnetic disk device that it has is connected, the maximum execution time of commands that remain in the device is guaranteed.

[0020]

Since the present invention is constructed as described above, it has the following effects. According to the present invention, since the user program interface on the host computer and the controller-to-controller control unit interface of the control unit mounted on the external storage means are realized as the same interface, the homogeneity of the system is assured, so that a plurality of hosts There is an effect that a system in which a computer shares a plurality of external storage means can be easily constructed and changed. In addition, the input / output instruction issued from the host computer is divided into a plurality of input / output instructions whose transfer length is suppressed to a certain amount or less, and the divided instructions are executed as independent instructions, respectively, from another host computer. Since the instructions can also be processed in parallel, there is an effect that the occupation of a specific host computer for a long time due to a large amount of data transfer can be prevented and service can be equalized. Further, in the data output process, the host computer is notified that the process is completed when the transfer data is stored in the data buffer in the external storage means, and in the data input process, the data is read from the external storage device to the data buffer. Since the data transfer process to another host computer can be executed at that time, there is an effect that it is possible to speed up the process of the entire system. In addition, a dedicated data buffer compatible with the host computer and a data buffer shared between unspecified host computers are provided, and the dedicated buffer is used when all the shared data buffers are in use, so the transfer process continues. Execution is guaranteed, and more buffers can be allocated to the host computer that transfers large amounts of data. Further, since the number of commands to be continuously output is limited to a certain number or less in advance and the next command group is sent after the execution of the previous command group is completed, the external storage device having the command relocation function can be used. Even when connected, the maximum execution time of the command staying in the device is guaranteed. Furthermore, the user program interface on the host computer and the controller interface to the external storage controller mounted on the external storage means are realized with the same standard interface, so there is no need to create special software and portability is ensured. There is an effect that is done.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a shared external storage device.

FIG. 2 is an explanatory diagram of a SCSI command format.

FIG. 3 is a diagram showing an example of a SCSI command issued from a host computer.

FIG. 4 is an example in which a SCSI command is decomposed into a plurality of SCSI commands by a host-side expansion device.

FIG. 5 is an explanatory diagram of a packet format used by the host-side control device, the packet switch, and the external storage device-side control device.

FIG. 6 is a configuration diagram showing a configuration when a plurality of external storage devices are connected.

FIG. 7 is a configuration diagram of an external storage device in a conventional example.

FIG. 8 is a diagram showing a format of CCW in the SCSI interface.

[Explanation of symbols]

10, 11, 12 Host computer sharing external storage device 29, 59 External storage device 31, 36 CPU unit in host computer 32, 37 IO bus for controlling peripheral devices 33, 38 SCS for controlling SCSI device
I controller 34, 39, 48, 56 SCSI bus 35, 40 Host side control device 41, 43, 44, 52 Signal cable for transmitting packet data to the next stage 42 Packet switch 45, 53 Control device 46 on external storage device side, 54 IO bus in external storage device 47, 55 SCSI controller 49, 50, 57, 58 Magnetic disk device 51 External storage expansion mechanism.

Claims (6)

[Claims] 1. In an external storage expansion method in which an external storage means is shared between a plurality of host computers, the host computer is connected to an arithmetic unit for executing a user program and the arithmetic unit via a first interface. A first controller control unit; and a first control unit that is connected to the first controller control unit and performs packet data transfer with an external exchange via a second interface different from the first interface. The external exchange performs processing for relaying a command from a plurality of host computers to the corresponding external storage means based on the packet data, and for relaying the processing result in the external storage means to the host computer. The packet received via the external exchange into the data buffer provided for the host computer is analyzed and the first An external storage device includes a second controller that issues a command to a second controller controller that is connected via the same interface as the interface, and the external storage device provides the second controller controller with the first interface. External storage expansion method characterized by being connected via the same interface. 2. The first control unit divides the transmission / reception command received from the first controller control unit into a plurality of blocks and packetizes each of them, and the packet is transmitted, and the second control unit has been divided and transmitted. The data transfer request from a plurality of host computers is executed in parallel in packet units by executing packet data as an independent command.
External memory expansion method described in item. 3. The second control unit notifies the host computer of the completion of processing in the data write process to the external storage device when all the packet data forming the write data from the host computer is received, In the process of reading data from the storage device, the second controller control unit can be switched to the data transfer process to another host computer at the time when all the data is taken in through the second controller control unit. The external storage expansion system according to claim 1, wherein: 4. The second control unit includes a data buffer provided for each host computer and a data buffer shared by unspecified host computers, and all the shared data buffers are in use. 2. The external storage expansion method according to claim 1, wherein a data buffer provided for the computer is used in such a state. 5. When a plurality of commands are simultaneously received and an external storage device having a function of optimizing the operation by appropriately changing the execution order of the commands internally is connected, the second control unit is The number of commands that are continuously issued to the second controller control unit is limited to a certain number or less in advance, and the next command group is sent after the execution of all the previously issued command groups is completed. The external storage expansion method according to claim 1. 6. The external storage expansion system according to claim 1, wherein the first interface is a SCSI interface.