File sharing system and method for storing and managing failure information based on statuses of a main control and a power supply

There is provided a file sharing system which allows accessing a memory that stores failure information and using the failure information even in a case where a CPU is shut down. When a failure occurs on a substrate, a control circuit on the substrate detects the failure and stores the information on the failure to an NVRAM. In a normal case, an OS loads the failure information and transmits it to a PC for maintenance. Upon shut down of the OS, a BMC loads the failure information from the NVRAM according to an instruction from the PC for maintenance. If an operator operates a manual switch upon power shut down, the BMC operates with the power supply from a battery, and the failure information is obtained from the NVRAM.

CROSS REFERENCES TO RELATED APPLICATIONS

This application relates to and claims priority from Japanese Patent Application No. 2008-185641, filed on Jul. 17, 2008, the entire disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a file sharing apparatus and a file sharing system.

2. Description of the Related Art

A file sharing apparatus is used for sharing data between/among multiple computers distributed over a network. As an initial file sharing apparatus, a file server is known which implements a file sharing protocol, such as a CIFS (or Common Internet File System) and an NFS (Network File System), to a generic OS (or Operating System). As an improved file sharing system, a NAS (or a Network Attached Storage) is known which supports multiple file sharing protocols (CIFS, NFS, DAFS (or Direct Access File System) and so on) by using a special OS which is specific to a file sharing service.

JP-A-2008-097527 discloses a file sharing apparatus that internally contains multiple controllers, whereby the controllers can backup the other party mutually. JP-A-2005-251060 and JP-A-2006-330506 also disclose a technology that displays a failure part though it is not a technology relating to a file sharing apparatus.

SUMMARY OF THE INVENTION

In a conventional file sharing apparatus, an OS manages a failure and may transmit it or give an alarm to an external apparatus. Therefore, in a case where the OS is terminated and is disabled to operate normally due to some failure, it is difficult to locate the occurring failure. It is further difficult to obtain information on the failure if a power supply apparatus, for example, has an abnormality and the entire apparatus is terminated therefor. If information on the failure is not available from the file sharing apparatus, enormous amounts of time and efforts are required for locating the occurring failure and clarifying the cause or causes.

The invention was made in view of the problem, and it is an object of the invention to provide a file sharing apparatus and a file sharing system by which information on a failure is available even in a case where a main control section is not operating normally or a case where power supply is shut down. Further objects of the invention will be apparent from the later description of embodiments.

In order to solve the problems, according to a first aspect of the invention, there is provided a file sharing apparatus that performs file sharing processing, the apparatus including a failure detecting section that detects the occurrence of a failure, a failure information storage section that stores failure information describing information on the detected failure, a main control section that performs the file sharing processing and obtains the failure information from the failure information storage section and transmits it to an apparatus for maintenance, a failure information managing section that obtains the failure information from the failure information storage section in a case where the main control stops operating, and a power supply unit that supplies a predetermined amount of power to each of the failure detecting section, the main control section and the failure information managing section.

The apparatus may further include a switch to be operated by a user for supplying backup power to predetermined components at least including the failure information storage section and the failure information managing section, wherein the failure information managing section operates in response to the supply of the backup power and obtains the failure information from the failure information storage section in a case where the main control section and the power supply unit stop.

The predetermined components may include multiple light emitting units, and the failure information managing section may cause the light emitting unit corresponding to the part having the failure among the light emitting units to light up or blink based on the obtained failure information.

The failure information managing section may transmit the obtained failure information to the apparatus for maintenance the address information of which is predefined as a destination.

The backup power supply may be an internal small power battery.

The backup power supply may be an external power supply to be externally supplied.

The external power supply may be provided within the apparatus for maintenance.

The failure information managing section and the failure information storage section may be provided on one same electronic circuit substrate.

The failure information managing section may operate based on an inquiry from the apparatus for maintenance and obtains the failure information from the failure information storage section in a case where the main control section stops and the power supply unit is operating normally.

The failure information managing section may transmit the obtained failure information to the apparatus for maintenance as a response to the inquiry from the apparatus for maintenance.

According to a second aspect of the invention, there is provided a file sharing apparatus that performs file sharing processing, the apparatus including a chassis, a first communication control substrate provided within the chassis, which communicates with a host computer, a second communication control substrate provided within the chassis, which communicates with a storage device, a main control substrate positioned within the chassis and connected to the first communication control substrate and the second communication control substrate, which performs the file sharing processing, a first failure detecting section provided on the first communication control substrate, which detects a failure occurring on the first communication control substrate, a second failure detecting section provided on the second communication control substrate, which detects a failure occurring on the second communication control substrate, a third failure detecting section provided on the main control substrate, which detects a failure occurring on the main control substrate, a failure information storage section provided on the first communication control substrate for storing failure information describing information on a failure detected by the failure information detecting section, a failure information managing section provided on the first communication control substrate for obtaining the failure information from the failure information storage section in a predetermined case, a power supply unit that supplies a predetermined amount of power to each of the substrates, and a switch to be operated by a user for supplying backup power to predetermined components at least including the failure information storage section and the failure information managing section, wherein the main control substrate obtains the failure information from the failure information storage section and transmits it to an apparatus for maintenance in a first case where the main control substrate and the power supply unit are operating normally, the failure information managing section operates based on an inquiry from the apparatus for maintenance and obtains the failure information from the failure information storage section in a second case where the main control substrate is not operating normally and the power supply unit is operating normally, and the failure information managing section operates in response to the supply of the backup power by an operation on the switch and obtains the failure information from the failure information storage section in a third case where the main control substrate and the power supply unit are not operating normally.

The failure information managing section may provide the obtained failure information to the outside in the second and third cases.

The failure information managing section may transmit the obtained failure information to the apparatus for maintenance in the second and third cases.

The chassis may have multiple light emitting units so as to visually check from the outside, and the failure information managing section may cause the light emitting unit corresponding to the part having the failure among the light emitting units to light up or blink based on the obtained failure information in the second and third cases.

According to the third aspect of the invention, there is provided a file sharing system including a file sharing apparatus that provides a file sharing service to a host computer and an apparatus for maintenance connected to the file sharing apparatus over a communication network for maintaining the file sharing apparatus, wherein the file sharing apparatus has a chassis, a failure detecting section provided within the chassis, which detects a failure occurring within the chassis, a failure information storage section provided within the chassis, which stores failure information describing information on the detected failure, a main control section provided within the chassis, which provides a file sharing service to a host computer and obtains the failure information from the failure information storage section and transmits it to the apparatus for maintenance, a failure information managing section provided within the chassis, which obtains the failure information from the failure information storage section and provides it to the apparatus for maintenance in a case where the main control section stops operating, and the apparatus for maintenance analyzes a failure based on the failure information obtained from one of the main control section and the failure information managing section and causes the result of the analysis to display on a screen.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to drawings, embodiments of the invention will be described below. According to an embodiment of the invention, failure information is made available based on an external trigger (such as an instruction by an operator and an inquiry from an apparatus for maintenance) in a case where a main control section and/or a power supply unit stop and failure information cannot be retrieved from a file sharing apparatus through a normal route, as will be described later.

First Embodiment

FIG. 1is an explanatory diagram showing an entire configuration of a file sharing system according to an embodiment to which the invention is applied. The file sharing system may include at least one file sharing apparatus (which will be called NAS)1, at least one storage device (which will be called storage), at least one PC for maintenance3, and at least one server4.

The NAS1is an apparatus that provides a file sharing service to the server4as the “host computer”. Details of the NAS1will be described later with reference toFIG. 2and soon. The storage2functioning as the “storage device” stores data received from the NAS1.

The storage2may include a physical storage device and a controller that controls the physical storage device (both of which are not shown), for example. The physical storage device may be a device from/to which data can be read/written, such as a hard disk device, a semiconductor memory device, an optical disk device, a magneto-optical disk device, a magnetic tape device and a flexible disk device.

In a case where a hard disk device is used as the storage device, an FC (or Fibre Channel) disk, a SCSI (or Small Computer System Interface) disk, a SATA disk, an ATA (or AT Attachment) disk or a SAS (Serial Attached SCSI) disk may be used, for example. In a case where a semiconductor memory device is used as the storage device, various memory devices can be used, such as a flash memory, an FeRAM (or Ferroelectric Random Access Memory), an MRAM (Magnetoresistive Random Access Memory), a phase change memory (or Ovonic Unified Memory), and a RRAM (or Resistance RAM).

The PC for maintenance3as the “apparatus for maintenance” may be configured as a personal computer or a server computer, for example. The PC for maintenance3manages the state of each NAS1and displays the presence of a failure on the screen of the PC for maintenance3.

Each NAS1and each storage2are connected over a communication network5such as an FC_SAN (or Fibre Channel_Storage Area Network). Each NAS1, the PC for maintenance3and each server4are connected over a communication network6such as a LAN (Local Area Network) and the Internet.

FIG. 2shows a block diagram showing a configuration of the NAS1. The square frame showing the external form of the NAS1also represents the chassis of the NAS1. The NAS1may include a main control substrate10, a first communication control substrate20, a second communication control substrate30, a cooling fan40, a power supply device50as the “power supply unit” and a switch60, for example.

The main control substrate10is a substrate that controls an operation of the NAS1. The main control substrate10may include a microprocessor11, a memory12, a control LSI (or Large-Scale Integrated circuit)13, and a light emitting diode14as the “light emitting unit”, for example.

The microprocessor (or CPU inFIG. 2)11loads and executes a program stored in the memory (or SRAM inFIG. 2)12. Thus, the main control substrate10performs a predetermined routine such as a file sharing processing. The memory12may be configured as an SRAM (or Static Random Access Memory) but may be any type of memory. At least a part of programs and data to be used by the microprocessor11can also be stored within the storage2.

The control LSI13may be configured as a programmable LSI such as an FPGA (Field Programmable Gate Array). The control LSI13may also be configured as a special LSI instead of an FPGA. The control LSI13performs a predetermined routine such as data transfer. For convenience, the microprocessor11, memory12and control LSI13will be called CPU11, SRAM12and FPGA13in the description below.

The first communication control substrate20is a substrate for communicating with each server4over the communication network6. The first communication control substrate20may include an environmental control LSI (or BMC: Base board Management Controller inFIG. 2)21, a non-volatile memory (or NVRAM inFIG. 2)22, an NIC (or Network Interface Card)23and a battery24, for example. The environmental control LSI21and the non-volatile memory22will be called BMC21and the NVRAM22, respectively, hereinafter.

The BMC21obtains failure information from the NVRAM22instead of the CPU11upon shut down of the main control substrate10(or upon OS shut down). The BMC21further feeds power to predetermined components (such as the NVRAM22, NIC23and light emitting diodes14,34,35and41) at a predetermined time when the power supply device50is shut down. The BMC21further controls the lighting of the light emitting diodes14,34,35and41distributed within the NAS1.

The NVRAM22is a memory for storing failure information collected on the substrates10,20and30. The failure information refers to information describing the position of occurrence or type of a failure. The memory for storing failure information is preferably a non-volatile memory. However, in some cases, a volatile memory backed up by a battery, for example, may be used.

The NIC23is a circuit for performing communication over the communication network6. The battery24corresponds to the “backup power supply” and may be configured as a small battery such as a button battery. The battery24is originally used for keeping times, for example. The light emitting diode14is associated with the FPGA13.

The second communication control substrate30is a substrate for communicating with each storage2over the communication network5. The second communication control section30may include an SFP (or Small Form-Factor Pluggable)31, a control LSI (or PXH inFIG. 2)32, an NIC33and the light emitting diodes34and35, for example.

The SFP31is a circuit for performing communication based on the Fibre Channel Protocol. The PXH32is a circuit that controls an operation of the second communication control substrate30. The NIC33is a circuit for performing communication over the communication network6. The light emitting diode34is associated with the SFP31. The light emitting diode35is associated with the PXH32.

The cooling fan40feeds external air into the chassis of the NAS1for cooling. The light emitting diode41is associated with the cooling fan40.

The power supply device50supplies power at a predetermined voltage to the substrates10,20and30and the cooling fan40within the NAS1. For convenience, the power supply device50connects to the NVRAM22, not shown, so that information can be stored in the NVRAM22upon occurrence of a failure.

Here, the “failure detecting section” may correspond to the CPU11, FPGA13, SFP31, PXH32and BMC21. The NVRAM22corresponds to the “failure information storage section”. The CPU11corresponds to the “main control section”. The BMC21corresponds to the “failure information managing section”.

FIG. 3is an explanatory diagram showing roles played by several circuits of the circuits of the NAS1. The CPU11and the SPRM12may operate an OS110, a file system (FS)111and an application program (App)112. The application program112may be a failover control program, for example.

The failover is processing for offloading the processing from one NAS1and placing it on another NAS1if the one NAS1stops. If one or multiple NAS1is or are failed and stops or stop among the multiple NAS1, a predetermined NAS1of the normally operating NAS1substitutes as the NAS1that is or are failed and stops or stop.

The FPGA13may include a data transfer section131and a failure detecting section132, for example. The data transfer section131is a function of performing data transfer between the SRAM12and the PXH32or NIC23. The failure detecting section132is a function of detecting a failure occurring within the main control substrate10and writing failure information on the failure to the NVRAM22.

The PXH32may include an option control section321and a failure detecting section322, for example. The option control section321is a function of controlling an operation of the second communication control substrate30, which is handled as an extensible option item. The failure detecting section322is a function of detecting a failure occurring within the second communication control substrate30and writing failure information on the failure to the NVRAM22.

The NVRAM22includes a register221for managing failure information. Details of the register221will be described later with reference toFIG. 4.

The BMC21may include a LAN communication section211, a failure detecting section212, a backup power supply control section213and a light emitting diode (or LED inFIG. 2) lighting control section214, for example. Here, it should be noted that the BMC21does not have control functions such as the OS and a file system, unlike the CPU11.

The LAN communication section211performs communication over the communication network6. The failure detecting section212has a function of detecting a failure occurring within the first communication control substrate20and storing failure information on the failure to a predetermined register221within the NVRAM22. The backup power supply control section213is a function of connecting the battery24to a predetermined component for power supply. The LED lighting control section214is a function for lighting up or blinking the light emitting diode corresponding to the part having a failure.

FIG. 4is an explanatory diagram showing examples of registers221(1) to221(8) provided within the NVRAM22. The register221(1) that manages a failure disabling the continuation of operations manages for which the continuation of an operation of NAS1is difficult, such as a BIOS (or Basic Input/Output System) abnormality, a hardware failure of the CPU11, a hardware failure of the cooling fan40(which is a state that all fans are disabled to operate) and a power supply abnormality.

The register221(2) that manages a failure for which the continuation of operations is possible manages a failure for which the continuation of an operation by the NAS1is possible, such as the occurrence of an instant power failure and a partial failure in the power supply device50or cooling fan40.

The register221(3) that manages a failure in a fan may manage which fan included in the cooling fan40has a hardware failure, for example. The register221(4) that manages a failure in a power supply unit may manage a cable disconnection to the power supply device50or a hardware failure of the power supply device50, for example. The register221(5) that manages a power supply failure may manage a failure that current at a predetermined voltage is not flowing on a substrate or that a predetermined voltage is not output from the power supply device50, for example. The register221(6) that manages a failure in the CPU may manage an abnormality in temperature of the CPU11or a hardware failure in the CPU11, for example. The register221(7) that manages an internal failure of a BMC may manage a failure occurring in a counter or a sequencer within the BMC21or a failure occurring in a register within the BMC21, for example. The register221(8) that manages a failure in an option card may manage a hardware failure in the second communication control substrate30, which is handled as an optional card, or a failure in an optical module (or SFP).

FIGS. 5A and 5Bare an explanatory diagram showing a configuration in which the BMC21feeds power from the battery24to a predetermined component. As shown inFIG. 5A, a switch circuit70for connection control is provided within the BMC21. For convenience of description, the light emitting diodes14,34,35,41are not discriminated inFIGS. 5A and 5B.

The switch circuit70includes multiple switches71. The switches71are connected to the light emitting diodes, NVRAM22and NIC23. A manual switch60is provided between the switch circuit70and the battery24. If the manual switch60is turned on, the power from the battery24is supplied to the BMC21, whereby the BMC21starts. Thus, the BMC21turns on the switches71of the switch circuit70, and the power from the battery24is supplied to the light emitting diodes, NVRAM22and NIC23.

As shown inFIG. 5B, the switch circuit70may be provided outside of the BMC21and may be configured to control by the BMC21.

With reference toFIGS. 6 to 8, failure management processing according to this embodiment of the invention will be described. The flowcharts described below illustrate a general outline of a processing routine and may be different from that of an actual computer program. So-called those skilled in the art can delete or change shown steps, change the order of the steps and/or add a new step.

First of all, the failure detecting sections (that is, the CPU11, FPGA13, BMC21, SFP31, PXH32, a fan40and power supply device50) within the NAS1stores information on a detected failure within the respective responsible range if any to the NVRAM22(S10). Information on a failure may be stored by setting a predetermined bit within a register according to the type of failure.

If the OS is in operation, that is, the NAS1is operating normally (S11: YES), the OS loads failure information from the NVRAM22(S12). The OS transmits the failure information from the NIC23to the PC for maintenance3over the communication network6.

The PC for maintenance3in response to the reception of the failure information (S14) analyzes the failure information to locate the occurring failure (S15) and displays the analysis result to the screen (S16). The PC for maintenance3can transmit an electronic mail to a pre-registered electronic mail address as required. The steps S11to S16relate to the processing in a case where the NAS1is operating normally, that is, the “first case”.

Referring to steps S30to S36, the “second case” will be described where power is supplied from the power supply device50but the main control substrate10is not operating normally. If the OS is not in operation (S11: NO), whether power is being supplied from the power supply device50or not is determined (S30). If power is being supplied from the power supply device50(S30: YES), the BMC21instead of the OS obtains failure information from the NVRAM22.

First of all, the BMC21determines whether any inquiry is received from the PC for maintenance3or not (S31), the details of which will be described later with reference toFIG. 7. If so (S31: YES), the BMC21loads failure information from the NVRAM22(S32). The BMC21transmits the failure information to the PC for maintenance3through the NIC23and over the communication network6(S33).

Subsequently, like the first case, the PC for maintenance3in response to the reception of failure information (S34) analyzes the failure information to locate the occurring failure (S35) and displays the analysis result to the screen (S36).

The third case where both of the main control substrate10and the power supply device50are not operating normally (S30: NO, then move to S50) will be described with reference toFIG. 8. Before the description, details (steps S31to S36) in the second case will be described with reference toFIG. 7.

An operator may operate a keyboard switch of the PC for maintenance3, for example, to instruct to start searching to the PC for maintenance3(S21). In response to the instruction, the PC for maintenance3transmits a packet indicating a request to the NAS1(S22).

Subsequently, as described with reference toFIG. 6, the BMC21in response to the reception of a request from the PC for maintenance3(S31: YES) loads failure information from the NVRAM22(S32) and transmits it to the PC for maintenance3(S33).

FIG. 8is a flowchart showing details of step S50inFIG. 6. In the “third case” where both of the main control substrate10and the power supply device50are not operating normally, an operator may turn on the manual switch60(S51). Thus, power from the battery24is supplied to the BMC21(S52), and the BMC21thus starts.

The BMC21determines whether the manual switch60has undergone an ON operation for a predefined time (such as approximately 5 seconds) or not (S53). If so (S53: YES), the BMC21controls the switch circuit70to connect a predetermined component and the battery24(S54). Thus, power is supplied from the battery24to the predetermined component (S55). At the times of steps S54and S55, the BMC21does not turn on the switches71connecting to the light emitting diodes.

Next, the BMC21loads failure information from the NVRAM22(S56). The BMC21controls the switch circuit70based on the failure information to light up or blink the light emitting diode corresponding to the position having the failure only for a predetermined period of time (S57). In other words, in step S57, power is not supplied to the light emitting diodes in steps S54and S55so as to light up or blink the required light emitting diode only.

Next, the BMC21transmits the failure information to a predetermined IP (or Internet Protocol) address (S58). For example, the IP address of the PC for maintenance3is predefined to the BMC21as the destination IP address.

Then, after shutting off the light emitting diode, the BMC21stops its operation and exits the processing (S59). Thus, the life of the battery24can be extended. An operator may turn on the manual switch60any number of times to check the lighting state of the light emitting diodes during a period that a predetermined or higher amount of electric energy remains in the battery24.

According to the first embodiment of the invention in the configuration above, failure information stored in the NVRAM22can be used even in a case where the main control substrate10is not operating normally. Therefore, the operation for locating a failure, for example, can be performed efficiently.

According to the first embodiment, when an operator turns on the manual switch60, the power of the battery24can be supplied to a predetermined component of the BMC21so that failure information stored in the NVRAM22can be used. Therefore, even in a case where the power supply device50is failed or has a power failure for a long period of time, the failure information can be used to perform a maintenance operation.

According to the first embodiment, even in a case where both of the main control substrate10and the power supply device50are not operating normally, the light emitting diode14,34,35or41corresponding to the failure may be lighted up or blink. Therefore, an operator can immediately locate the failure only by checking which light emitting diode is lighted on.

According to the first embodiment, even in a case where the main control substrate10is not operating normally, the failure information stored in the NVRAM22can be transmitted to the PC for maintenance3. Therefore, the PC for maintenance3can analyze the failure information and display the result on the screen.

According to the first embodiment, the small battery24internally contained in the NAS1can be used to load failure information from the NVRAM22or light up a light emitting diode. Therefore, the battery24for keeping times can be effectively used to increase the efficiency of a maintenance operation, without requiring the preparation of any special backup power supply such as a battery, for example.

According to the first embodiment, the NVRAM22functioning as the failure information storage section and the BMC21functioning as the failure managing section are mounted on the first communication control substrate20. Therefore, in a case where the power supply device50is failed, the power of the battery24can be supplied to the BMC21and the NVRAM22efficiently. As a result, the life of the battery24can be extended. Particularly, since the battery24is also provided on the same substrate20as that of the BMC21and NVRAM22, which are power consuming sections, a shorter electric path is only required therefor, which can reduce the number of wasteful voltage drops and can extend the life of the battery24.

According to the first embodiment, the BMC21transmits failure information to the PC for maintenance3according to a request from the PC for maintenance3. Thus, an operator can use the PC for maintenance3to use failure information at a remote place from the NAS1. Therefore, the efficiency of the maintenance operation can be improved.

According to the first embodiment, in response to the request from the PC for maintenance3, the BMC21transmits failure information to the PC for maintenance3. Therefore, the configuration can be simplified without requiring the registration of IP address of the PC for maintenance3to the BMC21in advance.

Second Embodiment

A second embodiment of a file sharing system to which the invention is applied will be described with reference toFIG. 9. Since the embodiments below correspond to change examples of the first embodiment, differences from the first embodiment will be described mainly.FIG. 9is a flowchart showing failure management processing according to the second embodiment.

According to the second embodiment, in a case where the main control substrate10is not operating normally but power is being supplied normally (that is, the second case), the BMC21transmits failure information to the pre-registered IP address, without waiting for a request from the PC for maintenance3(S33A). Since the IP address of the PC for maintenance3is pre-registered with the BMC21, failure information is automatically transmitted to the PC for maintenance3in the second case according to the second embodiment.

The second embodiment in the configuration above can also provide the same advantages as those of the first embodiment. Furthermore, according to the second embodiment, since failure information can be automatically transmitted to the PC for maintenance3without waiting for a request from the PC for maintenance3, the operability can be improved.

Third Embodiment

With referenceFIG. 10, a third embodiment of a file sharing system to which the invention is applied will be described. According to the third embodiment, in a case where both of the main control substrate10and the power supply device50are not operating normally (that is, the third case), the light emitting diode corresponding to the position having a failure is only lighted up (S57), and failure information is not transmitted to the PC for maintenance3. The third embodiment in the configuration above can also provide the same advantages to those of the first embodiment.

Fourth Embodiment

With reference toFIGS. 11 and 12, a fourth embodiment of a file sharing system to which the invention is applied will be described. According to this embodiment, USB (or Universal Serial Bus) bus power is used as a backup power supply in a case where the power supply device50is failed.

FIG. 11is a block diagram of the NAS1according to the fourth embodiment. The PC for maintenance3includes a LAN interface3A1and a USB interface3A2. The LAN interface3A1connects to the NIC23and33within the NAS1over the communication network6. The USB interface3A2connects to the USB interface25on the first communication control substrate20through a USB cable80.

The USB interface25on the first communication control substrate20is only for using the USB bus power and does not connect to the main control substrate10. However, without limiting thereto, the configuration is possible in which the USB interface25connects to the main control substrate10. The position where the USB interface25is to be mounted is not limited to the first communication control substrate20.

FIG. 12is a flowchart describing failure management processing in the third case according to the fourth embodiment. An operator may connect the PC for maintenance3and the NAS1through the USB cable80and turn on the manual switch60(S71). Thus, power from the battery24or the USB bus power is supplied to the BMC21(S72), and the BMC21starts.

The BMC21determines whether the manual switch60has undergone an ON operation for a predefined time or not (S73). If so (S73: YES), the BMC21connects a predetermined component and the battery24and the USB bus power (S74). Thus, power is supplied from the battery24or the USB bus power to the predetermined component (S75).

The BMC21loads failure information from the NVRAM22(S76) and lights up or blinks the light emitting diode corresponding to the position having the failure only for a predetermined period of time (S77). The BMC21transmits the failure information to a predefined IP address (S78). Finally, after shutting off the light emitting diode, the BMC21stops its operation and exits the processing (S79).

The fourth embodiment in the configuration above can also provide the same advantages as those of the first embodiment. Furthermore, according to the fourth embodiment, since the power within the PC for maintenance3is used as USB bus power, failure information can be obtained from the NVRAM22even at the end of the life of the battery24.

The invention is not limited to the aforesaid various embodiments. Those skilled in the art can perform various additions and/or changes thereon without departing from the scope of the invention. For example, instead of USB bus power, other external power application means such as IEEE (or Institute of Electrical and Electronic Engineers) bus power can be used. Alternatively, the BMC and the NVRAM may be integrated.