Abstract:
A storage device that is communicably connected to a host computer includes a plurality of disk units for storing data from the host computer. Each of the disk units includes a plurality of hard disks and is connected to one of a plurality of ports. A plurality of disk unit control units control the plurality of disk units, and each of the disk unit control units includes a memory for temporarily holding data from the host computer. A plurality of control signal transmission cables transmit control signals from the disk unit control units to the disk units. At least one of the control signal transmission cables is connected to at least two of the disk unit control units and transmits different control signals to at least two of the disk units. This enables device miniaturization and reduced costs for the storage device without a drop in reliability, even when a variety of devices are mounted in a highly dense configuration.

Description:
CROSS-REFERENCE TO PRIOR APPLICATION 
   This application relates to and claims priority from Japanese Patent Application No. 2004-70751, filed on Mar. 12, 2004 the entire disclosure of which is incorporated herein by reference. 
   FIELD OF THE INVENTION 
   The present invention relates to a storage device that is communicably connected to a host computer. 
   BACKGROUND OF THE INVENTION 
   Conventionally, in a storage device, port control logic circuits ( 503   1  to  503   4 ) of respective ports (ports  0  to  3 ) and drivers ( 505   1  to  505   4 ), all of which are mounted on a disk control substrate  501 , and receiver drivers ( 515   1  to  515   4 ) and port control circuits ( 517   1  to  517   4 ), all of which are mounted on respective disk drive substrates ( 513   1  to  513   4 ) on respective backboards ( 511   1  to  511   4 ) of a disk drive unit  509   1 , are connected by respective port-control signal cables ( 507   1  to  507   4 ), as shown in  FIG. 1 . Further, respective port control logic circuits ( 503   1  to  503   4 ) and respective drivers ( 505   1  to  505   4 ), receiver drivers ( 521   1  to  521   4 ) and port control circuits  523   1  to  523   4 ), all of which are mounted on respective disk drive substrates ( 519   1  to  519   4 ) on respective backboards ( 511   1  to  511   4 ) of a disk drive unit  509   2 , are connected via drivers ( 525   1  to  525   4 ) and separate port control signal cables ( 527   1  to  527   4 ), all of which are mounted on respective disk drive substrates ( 519   1  to  519   4 ). Further, as shown in  FIG. 2(   a ), four of each of an FC signal connector  529  and a port control signal connector  531  are arranged alternately along one edge of the disk control substrate  501 . 
   Furthermore, in the case of the conventional storage device detailed above, a plurality (two in  FIG. 3 ) of disk control substrates  553   1 ,  553   2  are mounted in the disk control unit  551 , as shown in  FIG. 3 , and a total of eight port control logic/FC control logic circuits ( 555   1  to  555   8 ) are mounted on each of the disk control substrates ( 553   1 ,  553   2 ) respectively so that there are four ports on each substrate. Next, the respective port control logic/FC control logic circuits ( 555   1  to  555   8 ) and individual disk drive substrates ( 561   1  to  561   8 ), which are arranged on respective backboards ( 559   1  to  559   4 ) in a disk drive unit  557 , are connected by two types of cable, which are Fiber Channel Interface FC signal cables (hereinafter abbreviated to ‘FC signal cables’) ( 563   1  to  563   8 ) and port control signal cables ( 565   1  to  565   8 ). Here, the port control signal cables ( 565   1  to  565   8 ) are cables for transmitting logic level signals required for controlling and monitoring the Fiber Channel Interface LSI and logic level signals required for monitoring the fault status of the parts and power supplies that constitute the disk drive unit  557 . 
   However, in the case of the storage device with the above constitution, the width region (mounting width) on the disk control substrate  501  that is required to connect the port control signal cables ( 565   1  to  565   8 ), which is occupied by a plurality (four in  FIG. 2 ) of port control signal connectors ( 531 ) that are arranged in a row on the disk control substrate  501 , is approximately 50 mm and comparatively large, as shown in  FIG. 2(   b ). For this reason, when port control signal connectors ( 531 ) for four ports are mounted on the same disk control substrate  501 , substantially the whole edge of the disk control substrate  501  is then used. This is because a space of about 32 mm is required in order to move a pair of connector lock levers  531   a  of the port control signal connector ( 531 ) shown in  FIG. 2(   b ) along the surface of the disk control substrate  501  when attaching or detaching the port control signal cables ( 565   1  to  565   8 ). Therefore, the number of respective port control logic/FC control logic circuits ( 555   1  to  555   8 ) mounted on the respective control substrates  501  is subject to restrictions and, hence, the mount number of the port control logic/FC control logic circuits ( 555   1  to  555   8 ) cannot be increased by exceeding the restricted number. 
   In addition, in the case of the storage device with the above constitution, port control signal cables ( 565   1  to  565   8 ), which connect the respective port control logic/FC control logic circuits ( 555   1  to  555   8 ) and the disk drive substrates ( 561   1  to  561   8 ) (mounted on the disk drive unit  557 ), are required for each port, and each port control signal cable ( 565   1  to  565   8 ) is wired on each disk drive substrate ( 561   1  to  561   8 ). Moreover, when the mount number of HDD (hard disk drives) is maximized in the disk drive unit  557 , the disk drive substrates ( 561   1  to  561   8 ) and HDD are mounted with high density. Therefore, the distance between the respective disk drive substrates ( 561   1  to  561   8 ) is then short, meaning that the port control signal cables ( 565   1  to  565   8 ) and FC signal cables ( 563   1  to  563   8 ) are intertwined within a short interval. As a result, the port control signal cable of port  0 , for example, is wrongly connected to the connector of another port, which means the problems of the device not operating normally readily occurs. 
   As is clear from the above description, conventionally, the number of port control logic/FC control logic circuits ( 555   1  to  555   8 ) that can be mounted on the disk control substrate ( 501 ) is restricted by the port control signal connectors, and, even with high integration of the port control logic/FC control logic circuits (FC control logic control LSI) ( 555   1  to  555   8 ) mounted on the disk control substrate ( 501 ), there is the problem that the number of controlled ports cannot be increased. In addition, because, in the disk drive unit ( 557 ), the same cables are wired in very close positions in accordance with the increase in the number of cables and the high density mounting, there is the problem that, as described above, an erroneous connection is easily made. Further, within a storage device with an increased number of connected cables, a space for wiring and fixing the cables is required, and there is therefore the problem that the storage device cannot be miniaturized. Further, there is also the problem that it is difficult to reduce the costs of the storage device due to the above-mentioned problems. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is a first object of the present invention to enable device miniaturization and reduced costs for the storage device without a drop in reliability even when a variety of devices are mounted highly densely therein. 
   Furthermore, it is a second object of the present invention to make it possible to prevent the erroneous wiring and erroneous connection of cables for connecting respective devices in the storage device even when a variety of devices are mounted highly densely therein. 
   The storage device according to the present invention is a storage device that is communicably connected to a host computer, comprising: a plurality of disk units for storing data from the host computer, each of the disk units comprising a plurality of hard disks and being connected to one of a plurality of ports; a plurality of disk unit control units for controlling the plurality of disk units, each of the disk unit control units being provided for each of the ports and comprising a memory for temporarily holding data from the host computer; and a plurality of control signal transmission cables for transmitting control signals from the disk unit control units to the disk units, wherein at least one of the control signal transmission cables is connected to at least two of the disk unit control units and transmits different control signals to at least two of the disk units. 
   In a preferred embodiment, each of the disk units comprises a port control circuit and a port bypass circuit in addition to the plurality of hard disks. 
   In a preferred embodiment, each of the disk unit control units comprises: a port control logic circuit for outputting a port control signal to the port control circuit of each of the disk units; and a fiber channel control logic circuit for outputting a fiber channel control signal to the port bypass circuit of each of the disk units. 
   In a preferred embodiment, said at least one of the control signal transmission cables is a port control signal cable for transmitting different port control signals from the port control logic circuits of said at least two of the disk unit control units to the port control circuits of said at least two of the disk units. 
   Further, in another preferred embodiment, said at least one of the control signal transmission cables is a fiber channel control signal cable for transmitting different fiber channel control signals from the fiber channel control logic circuits of said at least two of the disk unit control units to the port bypass circuits of said at least two of the disk units. 
   In a preferred embodiment, each of the disk units further comprises: a plurality of selectors that are used in order to change the number of ports that the storage device has, the selectors being connected to each of the control signal transmission cables and the respective port control circuits. 
   In a preferred embodiment, each of the selectors comprises a select input terminal to which a logic level “H” or logic level “L” voltage signal is applied, the selection of whether to capture a port control signal from each of the port control logic circuits being made in accordance with the logic level of the voltage signal thus applied to the select input terminal. 
   Moreover, in a preferred embodiment, each of the control signal transmission cables is connected to each of the disk control units via a plurality of connectors arranged on a disk control substrate for bearing the disk unit control units; and each of the connectors comprises: signal pins that allow at least two ports&#39; worth of the disk unit control units to be connected thereto; and a lock mechanism for attaching and fixing each of the control signal transmission cables. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing the details of a circuit constitution with which a conventional storage device is provided; 
       FIG. 2  is an explanatory view of a disk control substrate for mounting the port control logic circuit in  FIG. 1  and FC signal connectors and port control signal connectors that are disposed on the disk control substrate; 
       FIG. 3  is a block diagram showing an additional detailed circuit constitution of the conventional storage device; 
       FIG. 4  is a block diagram showing the overall constitution of a storage system to which the present invention is applied; 
       FIG. 5  is a block diagram showing the details of the circuit constitution with which the storage device according to an embodiment of the present invention is provided; 
       FIG. 6  is an explanatory view of a disk control substrate for mounting the port control logic circuit in  FIG. 5  and FC signal connectors and a 2-port control signal connector that are disposed on the disk control substrate; 
       FIG. 7  provides a comparison of the 2-port control signal connector shown in  FIG. 6  and a conventional 1-port control signal connector; 
       FIG. 8  is a block diagram showing the details of the circuit constitution with which a storage device according to a second modified example of an embodiment of the present invention is equipped; 
       FIG. 9  is a block diagram showing an example of an additional detailed circuit constitution of the storage device when an embodiment of the present invention is applied; and 
       FIG. 10  is a block diagram showing another example of an additional detailed circuit constitution of the storage device when an embodiment of the present invention is applied. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   An embodiment of the present invention will be described below in detail with reference to the drawings. 
     FIG. 4  is a block diagram showing the overall constitution of a storage system to which the present invention is applied. 
   The storage system  320  shown in  FIG. 4  comprises one or more channel adapters (CHA)  321 , one or more disk adapters (DKA)  322 , one or more cache memories (CACHE)  323 , one or more shared memories (SM)  324 , one or more common paths  325 , a plurality of physical storage devices (that is, storage devices)  326 , one or more connection control circuits  327 , one or more motherboards  328 , and one or more main supply devices  329 . A hard disk drive, nonvolatile semiconductor memory, or another type of device can be adopted for the physical storage devices  326 . However, hard disk drives (hereinafter abbreviated to ‘HDD’) are typically adopted. HDD will also be adopted in the following description. 
   The channel adaptors  321 , disk adapters  322 , cache memories  323 , and shared memories  324  are connected to one another by means of the common path  325 . The common path  325  may be provided in duplicate as illustrated (or as a multiplicity) in order to prepare for failure of the common path  325 . The channel adaptors  321  are connected to one or more host computers  310  or other storage systems (omitted from the illustration) by means of connecting wires  311 . The channel adaptors  321  control data transfers between the host computer  310  or another storage system (not illustrated), and the cache memories  323 . The disk adapters  322  control data transfers between the cache memories  323  and HDD  326 . The cache memories  323  are memories for the temporary storage of data received from the host computer  310  or another storage system (not illustrated) or data that is read from the HDD  326 . The shared memories  324  are memories that are shared by all the channel adapters  321  and all the disk adapters  322  in the storage system  320 . The shared memories  324  mainly store and hold various control and management information that is employed by the channel adaptors  321  and disk adapters  322 . 
   The motherboard  328  is an electrical circuit substrate comprising a data transfer wiring network for the HDD  326  and an electrical supply wiring network. A plurality of HDD  326  and two (or more) mutually interchangeable connection control circuits  327  are mounted on respective motherboards  328 . The two respective connection control circuits  327  on the respective motherboards  328  communicably connect the plurality of HDD  326  on the motherboard  328  to each of the mutually interchangeable two disk adapters  322 . A Fiber Channel Switch, a port bypass circuit, or the like, for example, is adopted for this purpose. The respective connection control circuits  327  and the plurality of HDD  326  are electrically connected via the wiring network on the respective motherboards  328 . Further, the respective connection control circuits  327  and respective disk adapters  322  are electrically connected via a multiplicity of cables, for example. Data transfers are executed between the plurality of HDD  326  and the respective disk adapters  322  via the respective connection control circuits  327 . A set, which is comprised of a connection control circuit  327  and disk adapter  322 , is provided in duplicate for each motherboard  328 , whereby the stability with respect to failure is improved. As will be described in specific terms subsequently, each HDD  326  is housed within a canister (that is, an enclosure) that can be mounted on or detached from the motherboard  328 . The pack of HDD  326  housed within this canister or enclosure can be called the ‘HDD pack’ or ‘HDD enclosure’. In the following description, a term such as ‘HDD pack’ will be used. 
   Each of the reference symbols  331 A,  331 B, and  331 C denote a group of HDD  326  according to the principles of RAID, which is known as a ‘parity group’ (or ‘error correction group’) according to the principles of RAID. Two or more HDD  326  that belong to the same parity group  331 A,  331 B, or  331 C are mounted on different motherboards and have data with redundancy stored thereon so that, even if one of the HDD  326  should fail, the data on the failed HDD  326  can be recovered by using the data on the other remaining HDD  326 . Two or more HDD  326  belonging to the same parity group  331 A,  331 B or  331 C desirably have exactly the same storage capacity, and, from that standpoint, are normally integrated in HDD of the same model from the same manufacturer, and therefore the same is also true for power supply specifications and data transfer interfaces. 
   The power supply system of the storage system  320  comprises one or more AC/DC power supply circuits  329 . The respective AC/DC power supply circuits  329  receive an input of AC power from an external AC power supply (a commercial 200V_AC power supply, for example)  330 , convert this power supply into DC electrical power of a predetermined voltage (56V, 48V, 24V, or 12V, or the like, for example), and then supply the converted DC supply to the plurality of HDD packs  333  on the motherboard  328  and to other circuits. The respective AC/DC power supply circuits  329  and the plurality of HDD packs  333  on the respective motherboards  328  are connected via a power supply wiring network on each motherboard  328 . In preparation for power failure, mutually interchangeable duplicate (or multiple) AC power supplies  330  are used. Duplicate AC/DC power supply circuits  329  or a larger number of multiple AC/DC power supply circuits  329  connected to each AC power supply  330  so as to be mutually interchangeable. In the illustrated example, the respective AC/DC power supply circuits  329  are shared by a plurality of motherboards  328 . However, as a modified example, one or more dedicated AC/DC power supply circuits may be provided for each motherboard  328 . 
   Further, a port relating to the present invention that is described below denotes a port between the respective disk adapters  322  above and respective motherboards (that is, disk drive units)  328 . 
     FIG. 5  is a block diagram showing the details of the circuit constitution with which the storage device according to an embodiment of the present invention is provided. 
   In  FIG. 5 , a disk drive unit (sometimes also described as a ‘disk array’ or ‘disk storage unit’; the same below)  1  comprises a backboard  3 . A basic unit of a disk drive substrate corresponding with port  0  (hereinafter described as the ‘basic disk drive substrate’)  5   1 , and two basic disk drive substrates of a basic disk drive substrate  5   2  corresponding with port  1 , which is a port adjacent to port  0 , for example, are arranged on the backboard  3 . In addition to the parts described above, an extension of the disk drive substrate corresponding with port  0  (hereinafter described as the ‘extension disk drive substrate’)  7   1 , and two extension disk drive substrates of an extension disk drive substrate  7   2  corresponding with port  1  are also arranged on the backboard  3 . 
   Two selectors  9  and  11 , each with two input terminals, one output terminal, and a select signal input terminal, and a port control circuit  13  and two drivers  15  and  17  are arranged on the basic disk drive substrate  5   1  that constitutes the basic disk drive substrate of port  0 . Similarly to the basic disk drive substrate  5   1 , two selectors  19  and  21  each with two input terminals and one output terminal, and a port control circuit  23  and two drivers  25  and  27  are arranged on the basic disk drive substrate  5   2  that constitutes the basic disk drive substrate of port  1 . Further, similarly to the basic disk drive substrates  5   1  and  5   2 , two selectors  29  and  31  each with two input terminals and one output terminal, and a port control circuit  33  and two drivers  35  and  37  are arranged on the extension disk drive substrate  7   1 , which is an extension disk drive substrate corresponding with port  0 . Further, similarly to the basic disk drive substrates  5   1  and  5   2  and the extension disk drive substrate  7   1 , two selectors  39  and  41  each with two input terminals and one output terminal, and a port control circuit  43  and two drivers  45  and  47  are arranged on the extension disk drive substrate  7   2 , which is an extension disk drive substrate corresponding with port  1 . Further, the selection may be switched depending on whether the select signal input terminals of the selectors ( 9 ,  11 ,  19 ,  21 ,  29 ,  31 ,  39 , and  41 ) are open or earthed, that is, depending on whether a logic level “H” voltage signal is applied to these select signal input terminals or a logic level “L” voltage signal is applied thereto. 
   On the other hand, the disk control logic unit  49  has the same circuit constitution as the disk adapter that the storage device comprises and is provided with a plurality of port control logic circuits  51   1 ,  51   2 , . . . ,  51   n-1 ,  51   n  with the same constitution provided in correspondence with the individual ports (port  0 , port  1 , . . . , port n- 1 , port n), and a plurality of drivers  53   1 ,  53   2 ,  53   n-1 ,  53   n  with the same constitution each of which is disposed in correspondence with respective port control logic circuits  51   1 ,  51   2 , . . . ,  51   n-1 ,  51   n . Each of the port control logic circuits  51   1 ,  51   2 , . . . ,  51   n-1 , and  51   n  and the respective drivers  53   1 ,  53   2 , . . . ,  53   n-1 , and  53   n  are individually connected, and the respective drivers  53   1 ,  53   2 , . . . ,  53   n-1 , and  53   n  and the respective basic disk drive substrates ( 5   1 ,  5   2 ) (provided for each port) are individually connected by respective port control signal cables ( 56 ,  58 , . . . ,  60 , and  62 ). 
   According to this embodiment, in order to connect the disk control logic unit  49  and disk drive unit  1 , a 2-port control signal cable ( 57   1 ,  57   n ), which has a constitution in which two port control signal cables (port control signal cable  56 , port control signal cable  58 , port control signal cable  60 , and port control signal cable  62 , for example) of adjacent ports (port  0 , port  1 , port n- 1 , and port n, for example) among the above-mentioned (plurality of) port control signal cables ( 56 ,  58 , . . . ,  60 , and  62 ) are bundled to form one cable, is adopted. 
   A port control signal outputted by the port control logic circuit  51   1  (corresponding with port  0 ) is inputted to selector  9  via the first input terminal of selector  9  (of the basic disk drive substrate  5   1 ) via the driver  53   1  and the port control signal cable  56  contained in the 2-port control signal cable  57   1 . Selector  9  is for selecting whether to input a control signal transmitted via a cable such as the 2-port control signal cable ( 57   1 ,  57   n ) or to input a signal via the backboard  3 , for example, this selection being determined by the mounting (connection) position of the disk drive substrate ( 5   1  on the backboard  3 . The select signal input terminal of the selector  9  is earthed in a predetermined position on the backboard  3  and the second input terminal is open, and a logic level “L” voltage signal is applied via the select signal input terminal. The selector  9  outputs, via the output terminal thereof, the above-mentioned port control signal, which has been inputted via the first input terminal, to the first input terminal of the selector  11 . First and second input terminals, which are input terminals for the control signals of the selector  9 , are allocated to one of the main edges of the disk drive substrate  5   1 , for example. 
   The selector  11  also permits selection of whether to input a control signal that is transmitted via a cable such as the 2-port control signal cable ( 57   1 ,  57   n ), or to input a signal via the backboard  3 , for example, the selection being determined by the mounting (connection) position of the disk drive substrate ( 5   1 ) on the backboard  3 . The select signal input terminal and second input terminal of the selector  11  are open and a logic level “H” voltage signal is applied via the select signal input terminal. The selector  11  outputs, via the output terminal thereof, the port control signal thus outputted by the selector  9  via the first input terminal to the port control circuit  13  and the driver  15 . The port control circuit  13  inputs the port control signal and executes a predetermined control operation based on the port control signal. Meanwhile, the driver  15  outputs the port control signal to the second input terminal of the selector  31  (of the extension disk drive substrate  7   1 ). 
   The selector  29  (of the extension disk drive substrate  7   1 ) earths the select signal input terminal and applies a logic level “L” voltage signal, and the first and second input terminals are both open. Further, the output terminal of the driver  35  (of the extension disk drive substrate  7   1 ) and the input and output terminals of the driver  37  are open respectively. The selector  31  outputs, via the output terminal thereof, the port control signal that is inputted via the second input terminal to the port control circuit  33  and driver  35 . The selectors  29  and  31  also permit selection of whether to input a control signal that is transmitted via a cable such as the above-mentioned 2-port control signal cable ( 57   1 ,  57   n ), or to input a signal via the backboard  3 , for example, the selection being determined by the mounting (connection) position of the (extension) disk drive substrate ( 7   1 ) on the backboard  3 . The port control circuit  33  has the port control signal inputted thereto and executes a predetermined control operation on the basis of the port control signal. 
   Next, the port control signal that is outputted by the port control logic circuit  51   2  (corresponding with port  1 ) is inputted to selector  19  via the second input terminal of the selector  19  (of the basic disk drive substrate  5   2 ) via the driver  53   2 , the port control signal cable  58  that constitutes the 2-port control signal cable  57   1 , and the driver  17  (of the basic disk drive substrate  5   1 ). The select signal input terminal of the selector  19  is open in a predetermined position on the backboard  3  and the first input terminal is open, and a logic level “H” voltage signal is applied via the select signal input terminal. The selector  19  outputs, via the output terminal thereof, the port control signal thus inputted via the second input terminal thereof to the first input terminal of the selector  21 . 
   The select signal input terminal and the second input terminal of the selector  21  are open and a logic level “H” voltage signal is applied thereto via the select signal input terminal. The selector  21  outputs, via the output terminal thereof, the port control signal thus outputted by the selector  19  via the first input terminal to the port control circuit  23  and driver  25 . The selectors  19  and  21  also permit selection of whether to input a control signal that is transmitted via a cable such as the above-mentioned 2-port control signal cable ( 57   1 ,  57   n ) or to input a signal via the backboard  3 , for example, this selection being determined by the mounting (connection) position of the (basic) disk drive substrate ( 5   2 ) on the backboard  3 . The port control circuit  23  inputs the port control signal and executes a predetermined control operation on the basis of the port control signal. Meanwhile, the driver  25  outputs the port control signal to the second input terminal of selector  41  (of the extension disk drive substrate  7   2 ) Further, the input terminal of the driver  27  and the output terminal are both open. 
   The select signal input terminal, first input terminal, and second input terminal of the selector  39  (of the extension disk drive substrate  7   2 ) are open. Further, the output terminal of driver  45  (of the extension disk drive substrate  7   2 ) and the input and output terminals of driver  47  are open respectively. The select signal input terminal of the selector  41  is open and a logic level “H” voltage signal is applied via the select signal input terminal. The selector  41  outputs, via the output terminal thereof, the port control signal thus inputted via the second input terminal to the port control circuit  43  and driver  45 . The port control circuit  43  has the port control signal inputted thereto and executes a predetermined control operation based on the port control signal. The selectors  39  and  41  also permit selection of whether to input a control signal that is transmitted via a cable such as the above-mentioned 2-port control signal cable ( 57   1 ,  57   n ) or to input a signal via the backboard  3 , for example, this selection being determined by the mounting (connection) position of the (extension) disk drive substrate ( 7   2 ) on the backboard  3 . 
   Further, the port control signal outputted via the port control logic circuit  51   n-1  (corresponding with port n- 1 ) is transmitted to a basic disk drive substrate  5   n-1  (not shown) via the driver  53   n-1  and the port control signal cable  60  of the 2-port control signal cable  57   n . Further, the port control signal outputted by the port control logic circuit  51   n  (corresponding with port n) is transmitted to the basic disk drive substrate  5   n  (not shown) via the driver  53   n  and the port control signal cable  62  that constitutes the 2-port control signal cable  57   n . 
     FIG. 6  is an explanatory view of a disk control substrate for mounting the port control logic circuits ( 51   1  to  51   n ) in  FIG. 5 , and FC signal connectors and a 2a-port control signal connector that are disposed on the disk control substrate. 
   As shown in  FIG. 6(   a ), FC signal connectors  61   1  and  61   2 , a 2-port control signal connector  63   1 , FC signal connectors  61   3  and  61   4 , a 2-port control signal connector  63   2 , FC signal connectors  61   5  and  61   6 , a 2-port control signal connector  63   3 , FC signal connectors  61   7  and  61   8 , and a 2-port control signal connector  63   4 , are arranged at respective predetermined intervals on the disk control substrate  59  along one edge thereof. That is, two FC signal connectors ( 61   1  to  61   8 ) per single port and one 2-port control signal connector ( 63   1  to  63   4 ) per single port are arranged respectively on the disk control substrate  59 . 
   The 2-port control signal connectors ( 63   1  to  63   4 ) have the same constitution and, therefore, only the 2-port control signal connector  63   1  will be taken as an example in the following description. 
   As shown in  FIG. 6(   b ), a larger number of signal pins (34 pins, for example) than the number of signal pins for the 1-port control signal connector (24 pins, for example) are arranged in the connector main body  65  of the 2-port control signal connector  63   1  in order that control signals for two ports are made to correspond with a single 2-port control signal connector ( 63   1 ). Further, a connector lock mechanism  67  for fixing the connector main body  65  to the disk control substrate  59  is disposed at the top of the connector main body  65 . Accordingly, the width of the connector main body  65  (22.59 mm, for example) can be established with substantially the same size as the whole width (21.59 mm, for example) of the signal pin placement region of the connector main body  65 . 
     FIG. 7  shows a comparison of the 2-port control signal connector shown in  FIG. 6  and a 1-port control signal connector. 
   In  FIG. 7(   a ), in the 1-port control signal connector  69 , the number of signal pins arranged on the connector main body  71  is 24 pins, and a pair of connector lock levers  73   1  and  73   2  are each turnably supported on an attachment portion at both ends of the connector main body  71 . In the case of a 1-port control signal connector  75  with the same constitution as the 1-port control signal connector  69 , the number of signal pins arranged on the connector main body  77  is 24 pins, and a pair of connector lock levers  79   1  and  79   2  are each turnably supported on an attachment portion at both ends of the connector main body  77 . 
   By providing the two 1-port control signal connectors ( 69  and  75 ) shown in  FIG. 7(   a ) in a row, the functions of the single 2-port control signal connector  63  shown in  FIG. 7(   b ) can be afforded (in other words, the result of integrating the two 1-port control signal connectors ( 69 ,  75 ) shown in  FIG. 7(   a ) is a single 2-port control signal connector ( 63 )). However, in this case, including the width of the 1-port control signal connectors  69  and  75 , and the width in a case where the connector lock levers  73   1  and  73   2  of the 1-port control signal connector  69  and the connector lock levers  79   1  and  79   2  of the 1-port control signal connector  75  are open, a mounting width of 124.48 mm is required. On the other hand, when the 2-port control signal connector  63  shown in  FIG. 7(   b ) is used, the mounting width of the disk control substrate  59  is then 41.59 mm, which is substantially one third of the above mounting width. As shown in  FIG. 6 , eight FC signal connectors ( 61   1  to  61   8 ) and four 2-port control signal connectors ( 63   1  to  63   4 ) can be mounted on the same disk control substrate ( 59 ). Accordingly, in the example shown in  FIG. 6 , an 8-port Fiber Channel Interface can be controlled by a single disk control substrate ( 59 ). 
     FIG. 8  is a block diagram showing the details of the circuit constitution with which a storage device according to the second modified example of an embodiment of the present invention is equipped. 
   In this modified example, the extension disk drive substrate  8  is connected to the port control logic circuit  51   3  of port  2  via the first input terminal of the selector  71 , the port control signal cable  64  constituting the 2-port control signal cable  57   2 , and the driver  53   3  of port  2 . Further, the extension disk drive substrate  10  is connected to the port control logic circuit  51   4  of port  3  via the second input terminal of the selector  81 , the driver  79  of the extension disk drive substrate  8 , the port control signal cable  66  constituting the 2-port control signal cable  57   2 , and the driver  53   4  of port  3 . 
   In the extension disk drive substrate  8 , the select input terminal of the selector  71  is earthed and a logic level “L” voltage signal is applied, and the second input terminal is open. Further, the select input terminal of the selector  73 , which is a selector for selecting whether to afford the constitution of the storage device a constitution that carries about two times the normal number of ports, for example, is also earthed and a logic level “L” voltage signal is applied, the second input terminal also being open. The output terminal of the driver  77  is also open. In the extension disk drive substrate  10 , the select input terminal of the selector  81  and the first input terminal are open, and the select input terminal of the selector  83 , which is a selector for selecting whether to afford the constitution of the storage device a constitution with two times the normal number of ports, for example, is also earthed and a logic level “L” voltage signal is applied, the second input terminal also being open. In addition, the output terminal of the driver  87 , and the input and output terminals of the driver  89  are also open. 
   The port control signal outputted by the port control logic circuit  51   3  (corresponding with port  2 ) is inputted to the selector  71  via the first terminal of the selector  71  (of the extension disk drive substrate  8 ) via the driver  53   3 , and the port control signal cable  64  of the 2-port control signal cable  57   2 . The port control signal is inputted from the output terminal of the selector  71  to the selector  73  via the first input terminal of the selector  73  and is outputted from the selector  73  to the port control circuit  75  and driver  77  via the output terminal of the selector  73 . 
   Furthermore, the port control signal, which is outputted from the port control logic circuit  51   4  (corresponding with port  3 ) is inputted to the selector  81  via the second input terminal of the selector  81  (of the extension disk drive substrate  10 ) via the driver  53   4 , the port control signal cable  66  of the 2-port control signal cable  57   2 , and the driver  79  (of the extension disk drive substrate  8 ). The port control signal is inputted from the output terminal of the selector  81  to the selector  83  via the first input terminal of the selector  83 , and then outputted from the selector  83  to the port control circuit  85  and driver  87  via the output terminal of the selector  83 . 
   Further, in  FIG. 8 , the same reference symbols are assigned to the same parts as those shown in  FIG. 5 , and therefore a detailed description thereof has been omitted. 
   According to an embodiment of the present invention or the modified examples thereof, in the case of the disk drive unit  1 , because the mounted state (storage capacity) of the HDD (hard disk drive) remain unchanged and the settings of the selectors ( 29 ,  31 ,  39 ,  41 ) of the extension disk drive substrates  71  and  72  shown in  FIG. 5  or the selectors ( 71 ,  73 ,  81 , and  83 ) of the extension disk drive substrates  8 ,  10  shown in  FIG. 6  are changed together with the form of cable connection, the constitution of the storage device can be freely changed to render a storage device with normal functions as shown in  FIG. 5  or a high-performance storage device with two times the normal number of ports as shown in  FIG. 8 . 
   Furthermore, when the constitution is changed from the storage device with the constitution shown in  FIG. 5  to the storage device with the constitution shown in  FIG. 8 , no new cables are used, and therefore erroneous cable connections can be prevented. 
     FIG. 9  is a block diagram showing an example of an additional detailed circuit constitution of the storage device when an embodiment of the present invention is applied. 
   In the case of the storage device shown in  FIG. 9 , the disk control unit  91  comprises disk control substrates  93  and  95  on which one chip (LSI) is disposed for each port and respective chips  97  to  111  function as port control logic/FC control logic circuits. Hereinbelow, each of the chips  97  to  111  will be described as port control logic/FC control logic circuits  97  to  111 . Meanwhile, the disk drive unit  113  comprises a plurality (two in  FIG. 9 ) of backboards  115  and  117 . The respective backboards  115  and  117  are provided with respective pluralities (four on each backboard for a total of eight in  FIG. 9 ) of disk drive substrates  119  to  133  and a multiplicity of HDD (hard disk drives)  135   1  to  135   n ,  137   1  to  137   n ,  139   1  to  139   n , and  141   1  to  141   n  aligned in a plurality of columns (two columns on each backboard for a total of four in  FIG. 9 ). 
   Further, a port control circuit  143   1  and a port bypass circuit  145   1  are arranged on the disk drive substrate  119 , a port control circuit  143   2  and a port bypass circuit  145   2  are arranged on the disk drive substrate  121 , a port control circuit  143   3  and a port bypass circuit  145   3  are arranged on the disk drive substrate  123 , a port control circuit  143   4  and a port bypass circuit  145   4  are arranged on the disk drive substrate  125  respectively. Further, a port control circuit  143   5  and a port bypass circuit  145   5  are arranged on the disk drive substrate  127 , a port control circuit  143   6  and a port bypass circuit  145   6  are arranged on the disk drive substrate  129 , a port control circuit  143   7  and a port bypass circuit  145   7  are arranged on the disk drive substrate  131 , and a port control circuit  143   8  and a port bypass circuit  145   8  are arranged on the disk drive substrate  133 . 
   The port control logic/FC control logic circuit  97  of port  0  and the port control circuit  143   1  on the disk drive substrate  119  are connected by a port control signal cable  151 , and the port control logic/FC control logic circuit  99  of port  1  and the port control circuit  143   3  on the disk drive substrate  123  are connected by a port control signal cable  153  respectively. The port control signal cables  151  and  153  constitute a 2-port control signal cable  150  between the disk control unit  91  and disk drive unit  113 . 
   The port control logic/FC control logic circuit  101  of port  2  and the port control circuit  143   5  on the disk drive substrate  127  are connected by a port control signal cable  155 , and the port control logic/FC control logic circuit  103  of port  3  and the port control circuit  143   7  on the disk drive substrate  131  are connected by a port control signal cable  157 . The port control signal cables  155  and  157  constitute a 2-port control signal cable  152  between the disk control unit  91  and disk drive unit  113 . 
   The port control logic/FC control logic circuit  105  of port  4  and the port control circuit  143   2  on the disk drive substrate  121  are connected by a port control signal cable  159 , and the port control logic/FC control logic circuit  107  of port  5  and the port control circuit  143   4  on the disk drive substrate  125  are connected by a port control signal cable  161 . The port control signal cables  159  and  161  constitute a 2-port control signal cable  154  between the disk control unit  91  and disk drive unit  113 . 
   The port control logic/FC control logic circuit  109  of port  6  and the port control circuit  143   6  on the disk drive substrate  129  are connected by a port control signal cable  163 , and the port control logic/FC control logic circuit  111  of port  7  and the port control circuit  143   8  on the disk drive substrate  133  are connected by a port control signal cable  165 . The port control signal cables  163  and  165  constitute a 2-port control signal cable  156  between the disk control unit  91  and disk drive unit  113 . 
   The port control logic/FC control logic circuit  97  performs communications with a host control logic unit (not shown) of a host computer or the like, for example, to exchange mutually required information. The port control logic/FC control logic circuit  97  outputs a port control signal to the port control circuit  143   1  via the port control signal cable  153  and a port control signal cable  151  that constitutes a 2-port control signal cable  150 . A process operation that is similar to that for the port control logic/FC control logic circuit  97  is also executed for the remaining port control logic/FC control logic circuits  99  to  111 . 
   The port bypass circuits  145   1  to  145   8  are Fiber Channel Switch chips (FC switch chips) (hereinafter abbreviated to ‘Fiber Channel Switch’), for example. By turning the Fiber Channel Switches  145   1  to  145   8  ON/OFF in accordance with instructions from the port control logic/FC control logic circuits ( 97  to  111 ) under the control of respective corresponding port control logic/FC control logic circuits ( 97  to  111 ), the respective HDD ( 135   1  to  135   n ,  137   1  to  137   n ,  139   1  to  139   n , and  141   1  to  141   n ) and the port control logic/FC control logic circuits ( 97  to  111 ) are disconnected/connected. 
   According to the above constitution, the number of cables required to connect the disk control units and disk drive units can be reduced in comparison with the conventional storage device shown in  FIG. 3 . 
     FIG. 10  is a block diagram showing another example of an additional detailed circuit constitution of the storage device when an embodiment of the present invention is applied. 
   The storage device shown in  FIG. 10  differs from the storage device shown in  FIG. 9  in that, in the disk control unit  191 , highly integrated chips (LSI) ( 197 ,  199 ,  201 , and  203 ) that singly function as a port-control logic/FC control logic circuit for two ports are arranged on a plurality (two in  FIG. 10 ) of disk control substrates  193  and  195 . As shown in  FIG. 9 , a port control signal cable that connects each of the two port control logic/FC control logic circuits contained in a single chip with the port control circuit of each chip disposed on the disk drive substrate is constituted as a 2-port control signal cable, as indicated by the reference symbols  200 ,  202 ,  204 , and  206 , between the disk control unit  191  and the disk drive unit  113 . In  FIG. 10 , a redundant constitution is rendered in which respective two port control logic/FC control logic circuits are allocated to each port ( 0  to  3 ) (chips  197  and  201  are allocated to port  0  and port  1  respectively, and chips  199  and  203  are allocated to port  2  and port  3  respectively). 
   Further, in  FIG. 10 , the same reference symbols are assigned to the same parts as those shown in  FIG. 9 , and, therefore, a detailed description of these parts is omitted. 
   According to the above constitution, in addition to it being possible to afford the same effects as those of the constitution shown in  FIG. 9 , by employing a highly integrated chip for the chip (LSI) constituting the disk control unit  191 , the mounting surface of the chips ( 197 ,  199 ,  201 , and  203 ) on the disk control substrates ( 193 ,  195 ) can be reduced, and hence miniaturization and cost reductions for the storage device are feasible. 
   According to the constitution shown in  FIG. 9  or  FIG. 10 , the FC control signal cables and port control signal cables for connecting the port control logic/FC control logic circuits ( 97  to  111 ) shown in  FIG. 9  or the chips ( 197  to  203 ) shown in  FIG. 10  with the port bypass circuits ( 145   1  to  145   8 ) are isolated, and the port control logic/FC control logic circuits ( 97  to  111 ) or the chips ( 197  to  203 ) shown in  FIG. 10  can be mounted highly densely on the disk control substrates( 93 ,  95 ,  193 ,  195 ) while securing signal isolation accuracy when an FC control signal is impaired due to cable faults. 
   Furthermore, the number of cables for connecting the disk control substrates ( 93 ,  95 ,  193 ,  195 ) and the disk drive substrates ( 119 ,  121 ,  123 ,  125 ,  127 ,  129 ,  131 ,  133 ) can be reduced to half the number of conventional cables used and cable ducts or similar can be reduced, meaning that miniaturization of the storage device is possible. 
   Moreover, because the number of cables used to connect the disk control substrates ( 93 ,  95 ,  193 ,  195 ) and the disk drive substrates ( 119 ,  121 ,  123 ,  125 ,  127 ,  129 ,  131 ,  133 ) can be reduced, the cable wiring, which easily grows complex, can be simplified, and hence the erroneous wiring of cables can be prevented. 
   In addition, depending on the specifications that the user requires for the storage device, in a state where the same disk control substrates ( 93 ,  95 ,  193 , and  195 ) and the same disk drive substrates ( 119 ,  121 ,  123 ,  125 ,  127 ,  129 ,  131 ,  133 ) are used, the addition of a new disk drive substrate or the like can be varied. It is thus possible to provide a storage device with a flexible constitution. 
   A preferred embodiment of the present invention and modified examples thereof were described hereinabove but merely serve as examples to illustrate the present invention, there being no intention to restrict the scope of the present invention to this embodiment or these modified examples alone. The present invention can also be implemented by means of a variety of other embodiments.