Abstract:
A storage device includes a plurality of interfaces for connection to an external device, a storage unit that stores data, an effective interface setting unit, and a switching instruction receiving unit. The effective interface setting unit sets one of the plurality of interfaces as an effective interface that may access the storage unit. The switching instruction receiving unit receives an effective interface switching instruction during operation of the storage device. The effective interface setting unit switches the interface set as the effective interface based on the effective interface switching instruction.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the priority based on a Japanese Patent Application No. 2008-218255 filed on Aug. 27, 2008, the disclosure of which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a storage device, and relates in particular to a storage device equipped with multiple interfaces for connection to an external device. 
     2. Description of Related Art 
     Hard disk drives, which are storage devices designed to store data, enjoy widespread use as one type of peripheral for personal computers. There are various different interfaces for connecting a computer and a hard disk drive. Such interfaces include, for example, the IEEE 1394 interface, the USB interface, and the LAN interface. 
     Hard disk drives that are equipped with multiple interfaces for connection to computers are known in the art. When a hard disk drive of this kind has been physically connected to a computer via the multiple interfaces, the hard disk drive will be operated by the computer through one interface ranked highest in a predetermined order of precedence, or through one interface representing the connection that was set up first, for example. 
     With the conventional hard disk drive mentioned above, it is not possible to switch the interface being used or to modify the order of precedence of the interfaces while the hard disk drive is connected to a computer and in use. Specifically, when it is desired to switch the interface or modify the order of precedence, it is necessary to first release the connection between the hard disk drive and the computer, for example, by unplugging the connecting cable or by rebooting. Accordingly, with conventional hard disk drives having multiple interfaces, there is room for improvement in terms of user convenience. 
     This problem is not limited to hard disk drives; rather, it is a problem common generally to storage devices having multiple interfaces. 
     SUMMARY 
     An object of the present invention is to provide a storage device with multiple interfaces, that would afford improved user convenience. 
     The present invention is addressed to attaining the above objects at least in part according to the following aspects of the invention. 
     Aspect 1. 
     A storage device comprising: 
     a plurality of interfaces for connection to an external device; 
     a storage unit that stores data; 
     an effective interface setting unit that sets one of the plurality of interfaces as an effective interface that may access the storage unit; and 
     a switching instruction receiving unit that receives an effective interface switching instruction during operation of the storage device, 
     wherein the effective interface setting unit switches the interface set as the effective interface based on the effective interface switching instruction. 
     According to the storage device of the aspect 1, one of the plurality of interfaces is set as the effective interface that may access the storage unit, and the interface set as the effective interface is switched on the basis of the effective interface switching instruction when the instruction is received during operation of the storage device, thereby affording improved user convenience in a storage device having multiple interfaces. 
     Aspect 2. 
     The storage device in accordance with aspect 1, wherein 
     one of the plurality of interfaces is a network interface for connection to a network, 
     the storage device further comprises a file sharing unit that provides a device on the network with a service for sharing a data file stored in the storage unit, and 
     prior to switching the interface set as the effective interface from the network interface to another interface, the effective interface setting unit has the file sharing unit stop providing the service for sharing a data file. 
     According to the storage device of the aspect 2, prior to switching the interface set as the effective interface from the network interface to another interface, the service for sharing a data file is stopped, thereby preventing device misoperation or corruption/loss of data resulting from the effective interface being switched while data is being transferred via the data file sharing service, and further improving operational stability and data reliability of the storage device. 
     Aspect 3. 
     The storage device in accordance with aspect 1, wherein 
     the effective interface setting unit opens a data transfer path between the storage unit and one of the plurality of interfaces that is to be set as the effective interface, and closes a data transfer path between the storage unit and the other interfaces. 
     According to the storage device of the aspect 3, one of the plurality of interfaces can be set as the effective interface enabling access to the storage unit, and the interface set as the effective interface can subsequently be switched based on the effective interface switching instruction. 
     Aspect 4. 
     The storage device in accordance with aspect 1, wherein 
     the plurality of interfaces are interfaces of mutually different type. 
     According to the storage device of the aspect 4, user convenience can be improved in a storage device having multiple interfaces of mutually different type. 
     Aspect 5. 
     The storage device in accordance with aspect 4, wherein 
     the plurality of interfaces include a USB interface and a LAN interface. 
     According to the storage device of the aspect 5, user convenience can be improved in a storage device having multiple interfaces including a USB interface and a LAN interface. 
     The present invention can be realized in various aspects. For example, the present invention can be realized in aspects such as a storage device; an interface switching method and device for a storage device; a computer program for accomplishing the functions of such a method or device; a recording medium having such a computer program recorded thereon; a data signal including such a computer program and carried on a carrier wave; and the like. 
     These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram depicting a configuration of a hard disk drive  100  according to Embodiment 1 of the present invention; 
         FIG. 2  is a flowchart depicting the flow of the switching process in the hard disk drive  100  according to Embodiment 1; 
         FIG. 3  is a diagram depicting a configuration of a hard disk drive  100   a  according to Embodiment 2 of the present invention; 
         FIG. 4  is a flowchart depicting the flow of the switching process in the hard disk drive  100   a  of Embodiment 2; 
         FIG. 5  is a diagram depicting a configuration of a hard disk drive  100   b  according to Embodiment 3 of the present invention; 
         FIG. 6  is a flowchart depicting the flow of the switching process in the hard disk drive  100   b  of Embodiment 3; 
         FIG. 7  is a diagram depicting a configuration of a hard disk drive  100   c  according to Embodiment 4 of the present invention; and 
         FIG. 8  is a flowchart depicting the flow of the switching process in the hard disk drive  100   c  of Embodiment 4. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The embodiments of the present invention are described below in the indicated order:
     A. Embodiment 1
       A-1: Device Configuration   A-2: Switching Process   
       B. Embodiment 2   C. Embodiment 3   D. Embodiment 4   E. Modified Embodiments   

     A. Embodiment 1 
     A-1: Device Configuration 
       FIG. 1  is a diagram depicting a configuration of a hard disk drive  100  according to Embodiment 1 of the present invention. The hard disk drive  100  of the present embodiment is a peripheral device that connects to a computer PC, and constitutes a storage device that is used to store data. The hard disk drive  100  has multiple interfaces. Specifically, the hard disk drive  100  can be connected to the computer PC through two interfaces, a USB interface and a LAN interface. 
     As shown in  FIG. 1 , the hard disk drive  100  has a hard disk drive unit (HDD unit)  110  that includes one or more hard disks for storing data; a USB port  120  for a USB connection to the computer PC; a LAN port  130  for a LAN connection to the computer PC; a selection switch  140  that allows the user to perform a switching operation of the effective interface, discussed later; and a CPU  150  for overall control of the hard disk drive  100 . 
     The CPU  150  includes a USB driver  151  for controlling data transfer in accordance with USB protocols; a LAN driver  152  for controlling data transfer in accordance with LAN protocols; a file share service module  153  for providing data file share services to computers PC on the network; an ATA driver  154  for controlling data transfer in accordance with ATA protocols; a bus switch  155  for switching the path of data transfer; an I/O port  156 ; and an interface switching decision module  157  for making decisions in relation to switching of the effective interface, discussed later. The functions of the elements included in the CPU  150  may be accomplished by having the CPU  150  load and execute computer programs that correspond to these elements, from an internal memory (not shown). 
     In the event that the hard disk drive  100  has been connected to the computer PC through the USB interface, the hard disk drive  100  will operate as a USB device of the computer PC to which the hard disk drive  100  has been directly connected. In this instance, data transfer between the computer PC and the HDD unit  110  will take place over a transfer path (herein also termed the “USB transfer path”) that leads from the computer PC to the USB port  120 , the USB driver  151 , the bus switch  155 , the ATA driver  154 , and the HDD unit  110 . On this path, data transfer between the USB port  120  and the USB driver  151  will take place in accordance with USB protocols, while data transfer between the ATA driver  154  and the HDD unit  110  will take place in accordance with ATA protocols, with protocol conversion between USB and ATA being carried out in the CPU  150 . 
     On the other hand, in the event that the hard disk drive  100  is connected to the computer PC through the LAN interface, the hard disk drive  100  will operate as an NAS (Network Attached Storage) shared by computers PC on the network. In this instance, exchange of data between the computer PC and the HDD unit  110  will take place over a transfer path (herein also termed the “LAN transfer path”) that leads from the computer PC to a router R, the LAN port  130 , the LAN driver  152 , the file share service module  153 , the bus switch  155 , the ATA driver  154 , and the HDD unit  110 . On this path, data transfer between the LAN port  130  and the LAN driver  152  will take place in accordance with LAN protocols, while data transfer between the ATA driver  154  and the HDD unit  110  will take place in accordance with ATA protocols, with protocol conversion between LAN and ATA being carried out in the CPU  150 . Also, in this instance, the data file share service  153  will provide the computers PC on the network with a sharing service of data files stored in the HDD unit  110 . 
     The selection switch  140  is a physical switch adapted to switch between two states corresponding to the two interfaces (the USB interface and the LAN interface). A signal that indicates the current state (i.e. a state corresponding one of the interfaces) of the selection switch  140  (this signal is also referred to herein as “switch state signal”) is input to the CPU  150  via the I/O port  156 . Depending on the input switch state signal, the interface switching decision module  157  will then make a decision in relation to switching the effective interface, discussed later. 
     Under the control of the interface switching decision module  157 , the bus switch  155  will toggle the switch to open up either the USB path or the LAN path discussed above, while closing the other. The interface corresponding to the transfer path that has been opened up by the bus switch  155  will then be established as the interface that may access the HDD unit  110  (hereinafter termed the “effective interface”). 
     The HDD unit  110  is equivalent to storage unit in the present invention; the selection switch  140  and the I/O port  156  are equivalent to the switching instruction receiving unit in the present invention; the interface switching decision module  157  and the bus switch  155  are equivalent to the effective interface setting unit in the present invention; and the file share service module  153  is equivalent to file sharing unit in the present invention. 
     A-2: Switching Process 
       FIG. 2  is a flowchart depicting the flow of the switching process in the hard disk drive  100  according to Embodiment 1. The switching process is a process that takes place during operation of the hard disk drive  100 , to switch the effective interface in response to a switching instruction. Switching of the effective interface refers to a process of changing the effective interface from the interface that is currently set as the effective interface to another interface that is identified by the switching instruction. 
     During startup of the hard disk drive  100 , the interface that corresponds to the state of the selection switch  140  will be set up as the effective interface. The switching process will be initiated when startup of the hard disk drive  100  is complete, and will continue to be executed continuously during operation of the hard disk drive  100 . 
     Of these effective interface switching choices, switching from the USB interface to the LAN interface could be carried out, for example, in the event that during use of the hard disk drive  100  as a USB device by the computer PC to which the hard disk drive  100  has been connected via the USB port, the user now wishes to share the HDD unit  110  with another computer PC on the network. On the other hand, switching from the LAN interface to the USB interface could be carried out, for example, in the event that the user wishes to achieve higher data transfer speed through a USB connection, while the computer PC to which the hard disk drive  100  is connected to by the LAN port  130  is using the hard disk drive  100  as an NAS. 
     In Step S 110  ( FIG. 2 ), the CPU  150  will determine whether there has been a switching operation of the selection switch  140  (i.e. whether there has been an effective interface switching instruction). Specifically, through polling via the I/O port  156 , the CPU  150  will monitor the switching state signal that represents the current state (corresponding to a particular interface) of the selection switch  140 , and if it determines that the switching state signal has changed, will determine that a switching operation of the selection switch  140  has taken place. 
     In Step S 120 , on the basis of the input switching state signal, the interface switching decision module  157  of the CPU  150  will determine whether the switching operation of the selection switch  140  is a switching operation to the LAN interface or a switching operation to the USB interface. Specifically, if the switching state signal is a signal that corresponds to the LAN interface, the interface switching decision module  157  will determine that the switching operation is an operation for switching from the USB interface to the LAN interface; or if the switching state signal is a signal that corresponds to the USB interface, it will determine that the switching operation is an operation for switching from the LAN interface to the USB interface. 
     If in Step S 120  the interface switching decision module  157  has determined that the switching operation is to the LAN interface, it will open up the LAN transfer path by switching the bus switch  155  (Step S 130 ). The HDD unit  110  will thereby be connected to the file share service module  153  and to the LAN driver  152 ; and sharing service of data files stored in the HDD unit  110  will be provided to the computers PC on the network. 
     On the other hand, if in Step S 120  the interface switching decision module  157  has determined that the switching operation is to the USB interface, it will shut down the file share service currently being provided by the file share service module  153  (Step S 140 ). Thus, the sharing service of data files that have been stored in the HDD unit  110  which was being provided to the computers PC on the network will terminate. Subsequently, the interface switching decision module  157  will open up the USB transfer path by switching the bus path  155  (Step S 150 ). The HDD unit  110  will thereby be connected to the USB driver  151 , and data storage service will be provided to the computer PC to which the hard disk drive  100  has been connected via the USB port  120 . 
     Subsequent to Steps  130  and S 150  of  FIG. 2 , the process will return to Step S 110  (state monitoring of the selection switch  140  by the CPU  150 ), and the above process will be executed again. 
     As discussed above, at any time during operation of the hard disk drive  100 , the hard disk drive  100  of Embodiment 1 is capable of switching of the effective interface without the need to disconnect the connection cable between the computer PC and the hard disk drive  100  or to restart the hard disk drive  100 . Thus, the hard disk drive  100  of Embodiment 1 affords improved user convenience in a storage device equipped with multiple interfaces. 
     Moreover, in the switching process that takes place in the hard disk drive  100  of Embodiment 1, when switching from the LAN interface to the USB interface, the file share service provided by the file share service module  153  will be shut down (Step S 140  of  FIG. 2 ) prior to switching by the bus switch  155  (Step S 150  of  FIG. 2 ), thereby proactively preventing device misoperation or corruption/loss of data resulting from the LAN transfer path being cut during data transfer between a computer PC and the HDD unit  110  via the file share service module  153 , and further improving operational stability and data reliability of the hard disk drive  100 . 
     B. Embodiment 2 
       FIG. 3  is a diagram depicting a configuration of a hard disk drive  100   a  according to Embodiment 2 of the present invention. The hard disk drive  100   a  of Embodiment 2 differs from the hard disk drive  100  of Embodiment 1 (see  FIG. 1 ) in that it also has a USB-ATA bridge  160  (a circuit for protocol conversion between USB and ATA) and a bus switch  170  adapted to switch the effective interface, these being provided as separate constitutional elements from the CPU  150   a . That is, while the CPU  150   a  provided to the hard disk drive  100   a  of Embodiment 2 has a LAN driver  152 , a file share service module  153 , an ATA driver  154 , an I/O port  156 , and an interface switching decision module  157 , it lacks a USB driver  151  and a bus switch  155 . The configuration of the hard disk drive  100   a  is otherwise comparable to Embodiment 1. 
     In Embodiment 2, where the hard disk drive  100   a  has been connected to a computer PC via a USB interface and is being operated as a USB device of the computer PC to which the hard disk drive  100   a  has been directly connected, data transfer between the computer PC and the HDD unit  110  will take place over a path (hereinafter also termed the “USB transfer path”) leading from the computer PC to the USB port  120 , the USB-ATA bridge  160 , the bus switch  170 , and then to the HDD unit  110 . On this transfer path, data transfer between the USB port  120  and the USB-ATA bridge  160  will take place by USB protocols, while data transfer from the USB-ATA bridge  160  to the HDD unit  110  will take place by ATA protocols, with protocol conversion between USB and ATA taking place in the USB-ATA bridge  160 . 
     On the other hand, where the hard disk drive  100   a  has been connected to a computer PC via a LAN interface and is being operated as an NAS that is shared by computers PC on the network, exchange of data between computers PC and the HDD unit  110  will take place over a path (hereinafter also termed the “LAN transfer path”) leading from the computer PC to a router R, the LAN port  130 , the LAN driver  152 , the file service sharing module  153 , the ATA driver  154 , the bus switch  170 , and thence to the HDD unit  110 . On this transfer path, data transfer between the LAN port  130  and the LAN driver  152  will take place by LAN protocols, while data transfer between the ATA driver  154  and the HDD unit  110  will take place by ATA protocols, with protocol conversion between LAN and ATA being performed in the CPU  150   a.    
     Under the control of the interface switching decision module  157 , the bus switch  170  will toggle the switch in order to open up either the aforementioned USB transfer path or LAN transfer path, while closing the other. The interface corresponding to the transfer path that has been opened through switching of the bus switch  170  will be set as the effective interface that may access the HDD unit  110 . 
     In Embodiment 2, the interface switching decision module  157  and the bus switch  170  are equivalent to the effective interface setting unit in the present invention. 
       FIG. 4  is a flowchart depicting the flow of the switching process in the hard disk drive  100   a  of Embodiment 2. In the switching process of Embodiment 2, the particulars of Steps S 110  and S 120  are the same as in Embodiment 1 (see  FIG. 2 ). 
     If in Step S 120  it has been determined that the switching operation is to the LAN interface, the interface switching decision module  157  ( FIG. 3 ) will open up the LAN transfer path by switching the bus path switch  170  (Step S 132 ). The HDD unit  110  will thereby be connected to the file share service module  153  and to the LAN driver  152 ; and sharing service of data files stored in the HDD unit  110  will be provided to the computers PC on the network. 
     On the other hand, if in Step S 120  it has been determined that the switching operation is to the USB interface, the interface switching decision module  157  will shut down the file share service currently being provided by the file share service module  153  (Step S 140 ), and open up the USB transfer path by switching the bus switch  170  (Step S 152 ). Thus, the HDD unit  110  will be connected to the USB-ATA bridge  160 , and data storage service will be provided via the USB port  120  to the computer PC to which the hard disk drive  100   a  has been connected. 
     As discussed above, as in Embodiment 1, at any time during operation of the hard disk drive  100   a  of Embodiment 2, the hard disk drive  100   a  will be able to switch the effective interface without the need to disconnect the connection cable between the computer PC and the hard disk drive  100   a  or to restart the hard disk drive  100   a , so improved user convenience can be attained in a storage device equipped with multiple interfaces. Moreover, when switching from the LAN interface to the USB interface, the file share service provided by the file share service module  153  will be shut down (Step S 140  of  FIG. 4 ) prior to switching by the bus switch  170  (Step S 152  of  FIG. 4 ), thereby proactively preventing device misoperation or corruption/loss of data resulting from the LAN transfer path being cut during data transfer between a computer PC and the HDD unit  110  via the file share service module  153 , and further improving operational stability and data reliability of the hard disk drive  100   a . Additionally, because the hard disk drive  100   a  of Embodiment 2 employs a dedicated circuit, namely, the USB-ATA bridge  160 , for protocol conversion between USB and ATA, faster data transfer speeds can be achieved during use as a USB device. 
     C. Embodiment 3 
       FIG. 5  is a diagram depicting a configuration of a hard disk drive  100   b  according to Embodiment 3 of the present invention. The hard disk drive  100   b  of Embodiment 3 differs from the hard disk drive  100  of Embodiment 1 shown in  FIG. 1  in terms of its arrangement for receiving effective interface switching instructions. Specifically, the hard disk drive  100   b  of Embodiment 3 lacks the physical switch represented by the selection switch  140  (see  FIG. 1 ), and instead has a Web service module  158  whereby the CPU  15  receives switching instructions. The configuration of the hard disk drive  100   b  is otherwise similar to Embodiment 1. 
     The Web service module  158  uses the Web to deliver various services to Web clients which have been provided on the computers PC. These services include, for example, an initial setting service for carrying out initial settings of the hard disk drive  100   b , as well as an effective interface switching service. Specifically, when the Web client provided on a computer PC issues a command instructing switching of the effective interface, the Web service module  158  will receive the command via the network, and will prompt the interface switching decision module  157  to switch the effective interface. In Embodiment 3, the Web service module  158  is equivalent to switching instruction receiving unit in the present invention. 
     The elements that make up the USB transfer path and the LAN transfer path in the hard disk drive  100   b  of Embodiment 3, as well as the protocols used for data transfer, are the same as in Embodiment 1 (see  FIG. 1 ). 
       FIG. 6  is a flowchart depicting the flow of the switching process in the hard disk drive  100   b  of Embodiment 3. In Step S 112 , the CPU  150   b  will determine whether an effective interface switching command has been received from the computer PC. Specifically, the CPU  150   b  will wait for the Web service module  158  to receive a command issued by the Web client of the computer PC and instructing that the effective interface be switched. Upon receiving the command, the process will advance to Step S 120 . The processing particulars of the subsequent steps (Steps S 120  to S 150  of  FIG. 6 ) are the same as in Embodiment 1 depicted in  FIG. 2 . 
     As discussed above, as in Embodiment 1, in the switching process in the hard disk drive  100   b  of Embodiment 3, switching of the effective interface can be accomplished at any time during operation of the hard disk drive  100   b , without the need to disconnect the connection cable between the computer PC and the hard disk drive  100   b  or to restart the hard disk drive  100   b , so improved user convenience can be attained in a storage device equipped with multiple interfaces. Moreover, when switching from the LAN interface to the USB interface, the file share service provided by the file share service module  153  will be shut down (Step S 140  of  FIG. 6 ) prior to switching by the bus switch  155  (Step S 150  of  FIG. 6 ), thereby proactively preventing device misoperation or corruption/loss of data resulting from the LAN transfer path being cut during data transfer between a computer PC and the HDD unit  110  via the file share service module  153 , and further improving operational stability and data reliability of the hard disk drive  100   b.    
     In the event that the switching command issued by the computer PC is a switching command from the USB interface to the LAN interface, a process to verify that the connection to the hard disk drive  100   b  being used as a USB device has been released may be carried out in the computer PC prior to switching by the bus switch  155  (Step S 130  of  FIG. 6 ). Specifically, the hard disk drive  100   b  may wait to receive from the Web client of the computer PC a command indicating that release of the connection is complete; and after having received the command, proceed to execute the process of Step S 130 . In this case, the Web client may bring up on the display of the computer PC a message prompting the user to release the connection to the hard disk drive  100   b  being used as a USB device. By so doing, the connection between the computer PC and the hard disk drive  100   b  being used as a USB device will be released prior to switching by the bus switch  155  (Step S 130 ), thus proactively preventing device misoperation or corruption/loss of data resulting from the USB transfer path being cut during data transfer between the computer PC and the HDD unit  110  via the USB interface, and further improving operational stability and data reliability of the hard disk drive  100   b.    
     It is not essential that effective interface switching instructions to the hard disk drive  100   b  from a computer PC be made via the Web. Specifically, as depicted in  FIG. 5 , in another acceptable arrangement the computer PC could be provided with a dedicated command issuing software designed to issue commands for controlling the hard disk drive  100   b ; and effective interface switching instructions could be made through receipt by the CPU  150   b  of the hard disk drive  100   b  of dedicated commands issued from the computer PC. 
     D. Embodiment 4 
       FIG. 7  is a diagram depicting a configuration of a hard disk drive  100   c  according to Embodiment 4 of the present invention. The hard disk drive  100   c  of Embodiment 4 differs from the hard disk drive  100   b  of Embodiment 3 (see  FIG. 5 ) in that it is furnished with a USB-ATA bridge  160  (a circuit for protocol conversion between USB and ATA), and a bus switch  170  adapted to switch the effective interface, these being provided as separate constitutional elements from the CPU  150   c . That is, while the CPU  150   c  provided to the hard disk drive  100   c  of Embodiment 4 has a LAN driver  152 , a file share service module  153 , an ATA driver  154 , an interface switching decision module  157 , a Web service module  158 , and an I/O port  159 , it lacks a USB driver  151  and a bus switch  155 . The configuration of the hard disk drive  100   c  is otherwise comparable to Embodiment 3. 
     The elements that make up the USB transfer path and the LAN transfer path in the hard disk drive  100   c  of Embodiment 4, as well as the protocols used for data transfer, are the same as in Embodiment 2 (see  FIG. 3 ). In Embodiment 4, the interface switching decision module  157  and the bus switch  170  are equivalent to the effective interface setting unit in the present invention; and the Web service module  158  is equivalent to switching command receiving unit in the present invention. 
       FIG. 8  is a flowchart depicting the flow of the switching process in the hard disk drive  100   c  of Embodiment 4. In the switching process of Embodiment 4, the particulars of Step S 112  are the same as in Embodiment 3 shown in  FIG. 6 . The particulars of Step S 120  and subsequent steps (Steps S 120  to S 152  of  FIG. 8 ) are the same as in Embodiment 2 shown in  FIG. 4 . 
     As discussed above, as in Embodiment 1, at any time during operation of the hard disk drive  100   c  of Embodiment 4, the hard disk drive  100   c  is capable of switching the effective interface without the need to disconnect the connection cable between the computer PC and the hard disk drive  100   c  or to restart the hard disk drive  100   c , so improved user convenience can be attained in a storage device equipped with multiple interfaces. Moreover, when switching from the LAN interface to the USB interface, the file share service provided by the file share service module  153  will be shut down (Step S 140  of  FIG. 8 ) prior to switching by the bus switch  170  (Step S 152  of  FIG. 8 ), thereby proactively preventing device misoperation or corruption/loss of data resulting from the LAN transfer path being cut during data transfer between a computer PC and the HDD unit  110  via the file share service module  153 , and further improving operational stability and data reliability of the hard disk drive  100   c . Additionally, because the hard disk drive  100   c  of Embodiment 4 employs a dedicated circuit, namely, the USB-ATA bridge  160 , for protocol conversion between USB and ATA, faster data transfer speeds can be achieved during use as a USB device. 
     As in Embodiment 3, in Embodiment 4, in the event that the switching command issued by the computer PC is a switching command from the USB interface to the LAN interface, a process to verify that the connection to the hard disk drive  100   c  being used as a USB device has been released may be carried out in the computer PC prior to switching by the bus switch  170  (Step S 132  of  FIG. 8 ). Also, as in Embodiment 3, in Embodiment 4 it is not essential that effective interface switching instructions to the hard disk drive  100   c  from a computer PC be made via the Web; as depicted in  FIG. 7 , in another acceptable arrangement the computer PC could be provided with a dedicated command issuing software designed to issue commands for controlling the hard disk drive  100   c ; and effective interface switching instructions could be made through receipt by the CPU  150   c  of the hard disk drive  100   c  of dedicated commands issued from the computer PC. 
     E. Modified Embodiments 
     While the present invention has been shown above through certain preferred embodiments, the invention is in no way limited to these embodiments, and without departing from the spirit of the invention may be reduced to practice in various other modes, such as the following modifications for example. 
     E1. Modified Embodiment 1 
     The hard disk drive  100  configurations described in the preceding embodiments are merely exemplary, and various possible modifications may be made thereto. For example, whereas in the preceding embodiments the hard disk drive  100  is furnished with two interfaces, the hard disk drive  100  may instead be provided with three or more interfaces. In this instance as well, the interface to be set as the new effective interface from among the three or more interfaces will be identified through an effective interface switching instruction (a switch state signal or command as described in the preceding embodiments). 
     The interfaces provided to the hard disk drive  100  are not limited to a USB interface and a LAN interface, and other interfaces (e.g. an IEEE 1394 interface or wireless LAN interface) may be provided as well. The hard disk drive  100  may also be provided with multiple interfaces of the same type. 
     In the preceding embodiments, the hard disk drive  100  has a file share service module  153 , but it is not essential for the hard disk drive  100  to have a file share service module  153 . 
     Some of the arrangements implemented through hardware in the preceding embodiments may instead be implemented through software, and conversely some of the arrangements implemented through software may instead be implemented through hardware. For example, in Embodiment 2 (see  FIG. 3 ), protocol conversion between USB and ATA is carried out through hardware, namely, the USB-ATA bridge  160 , but protocol conversion between LAN and ATA may be carried out analogously through hardware. 
     The present invention is not intended to be limited to a hard disk drive  100  furnished with an HDD unit  110 , and is applicable generally to storage devices having a storage unit for storing data. 
     E2. Modified Embodiment 2 
     In the preceding embodiments, switching operations by the selection switch  140  were monitored through polling by the CPU  150 ; however, switching operations by the selection switch  140  may be accompanied by a signal indicating that a switching operation has occurred being sent from the selection switch  140  to the CPU  150 .