Abstract:
A power supply control device including: a control unit which controls power supplied from a first device to a disk array unit accessible from host devices through a network device; and a second device which supplies power to the disk array unit and the power supply control device when the power supply from the first device is disconnected, the control unit including: a collecting unit which collects power supply fault information regarding at least one of the host devices and the network device; a starting unit which starts power supply from the second device when power supplied from the first device is disconnected; and a transmitting unit which transmits a notification to the disk array unit in response to collection of power supply fault information after starting the power supply from the second device, the notification indicating that the power supplied from the first device is disconnected.

Description:
[0001]    This application is based upon and claims the benefit of priority from Japanese patent application No. 2009-216119, filed on Sep. 17, 2009, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND 
       [0002]    The embodiments of the present invention relate to a power supply control device, a storage system, a control method of the power supply control device, a control method of a disk array unit and a computer readable medium thereof. More particularly, it relates to a method for controlling power supply of a disk array unit that can perform multi-platform connection with a plurality of host devices with different power supply control specifications. 
         [0003]    In order to improve the response of write processing from a host device, the disk array unit notifies the host device of writing completion when the disk array unit completes writing data in cache memory. The disk array unit writes data held in the cache memory to a hard disk drive when the host device is not writing other data in the cache memory. 
         [0004]    For this reason, the disk array unit has a battery, etc. in preparation for when electric power is not supplied to the disk array unit due to a power failure, etc. in a state where data exists in the cache memory. The disk array unit backs up the data held in the cache memory by using the battery. 
         [0005]    Examples of the disk array unit technology are disclosed below. 
         [0006]    Patent Document 1 discloses a disk array unit which has a cache saving area of a recording medium that is formed in an area that is different from a user data area of the recording medium. When a power failure occurs, the disk array unit copies contents of the cache memory into the cache saving area of the recording medium by using a back up power supply. 
         [0007]    Patent Document 2 discloses that a management device manages an external storage device of the disk array unit by using simple network management protocol (SNMP). Patent Document 2 also discloses that when abnormalities occur in a main power supply of the external storage device, the disk array unit supplies electric power from an auxiliary power supply to a semiconductor memory, a hard disk, and a control unit. 
         [0008]    [Patent Document 1] JP-A-2000-357059 
         [0009]    [Patent document 2] JP-A-2003-150415 
         [0010]    In Patent Document 1 and Patent Document 2, the uninterruptible power supply device supplies electric power when a power supply failure of the disk array unit occurs. However, software for controlling the uninterruptible power supply device is needed, and the specification for controlling the uninterruptible power supply differs according to the company that makes the uninterruptible power supply. For this reason, there is a problem that, when managing the plurality of host devices and the disk array units with different power supply control specifications collectively, management of the power supply is very complicated. 
         [0011]    A purpose of certain embodiments of the present s is to provide a power supply control device which can easily control the power supply of a storage system that comprises a plurality of host devices and disk array units with different power supply control specifications and which does not lose the data held in the cache memory. 
       SUMMARY OF THE INVENTION 
       [0012]    An exemplary object of the embodiments of the present invention is to provide a power supply control device, a storage system, a control method of the power supply control device, a control method of a disk array unit and a computer readable medium thereof in order to easily control the power supply of the storage system that comprises a plurality of host devices and disk array units with different power supply control specifications and which does not lose the data held in the cache memory. 
         [0013]    According to one aspect of the embodiments of the present invention, a power supply control device comprising: a power supply control unit configured to control electric power supplied from a first power supply device to a disk array unit which is accessible from a plurality of host devices through a network device and from the power supply control device, at least two of the plurality of host devices operate with different power supply control specifications, and a second power supply device configured to supply electric power to the disk array unit and the power supply control device when the electric power supply from the first power supply device is disconnected, wherein the power supply control unit comprises: a collecting unit configured to collect power supply fault information indicating a power supply failure of at least one of the plurality of host devices and the network device, wherein the power supply fault information is transferred according to a management control protocol which controls both the plurality of host devices and the network device; a starting unit configured to start the supply of the electric power from the second power supply device when the electric power supplied from the first power supply device is disconnected; and a transmitting unit configured to transmit a notification to the disk array unit in response to the collection of the power supply fault information according to the management control protocol after starting the electric power supply from the second power supply device, wherein the notification indicates that the electric power supplied from the first power supply device is disconnected. 
         [0014]    According to one aspect of the embodiments of the present invention, a power supply control method of a power supply control device, comprising: controlling electric power supplied from a first power supply device to a disk array unit which is accessible from a plurality of host devices through a network device and from the power supply control device, at least two of the plurality of host devices operate with different power supply control specifications, in a power supply control step, and supplying electric power to the disk array unit and the power supply control device when the electric power supply from the first power supply device is disconnected in a second power supply steps, wherein the power supply control step comprises: collecting power supply fault information indicating a power supply failure of at least one of the plurality of host devices and the network device in a collecting step, wherein the power supply fault information is transferred according to a management control protocol which controls both the plurality of host devices and the network device; starting the supply of the electric power from the second power supply device when the electric power supplied from the first power supply device is disconnected in a starting step; and transmitting a notification to the disk array unit in response to the collection of the power supply fault information according to the management control protocol after starting the electric power supply from the second power supply device in a transmitting step, wherein the notification indicates that the electric power supplied from the first power supply device is disconnected. 
         [0015]    According to one aspect of the embodiments of the present invention, a control method of a disk array unit, wherein the disk array unit comprises a first controller and a plurality of disks and is connected to a power supply control device which controls a first power supply device and a second power supply device, comprising: a host control unit collecting I/O (Input/Output) commands from a plurality of host devices; a disk control unit controlling transmission/reception of the data with the disks; storing the data in a cache memory; and processing the I/O commands which the host control unit has collected when the notification is received from the power supply control device, wherein the notification indicates that the electric power supplied from the first power supply device is disconnected, stopping power supplied from the second power supply device to the host control unit and the disk control unit after all the I/O commands the processing unit has collected have been processed, in a stopping step, saving the data stored in the cache memory to a predetermined recording medium in the disk array unit after the stopping step, and transmitting a request to the power supply control device, wherein the request is for stopping the power supply from the second power supply device to the disk array units in response to saving the data stored in the cache memory to the disk array unit. 
         [0016]    According to one aspect of the embodiments of the present invention, a computer readable medium recording thereon a program for enabling computer to execute a power supply control method of a power supply control device, the power supply control method comprising: controlling electric power supplied from a first power supply device to a disk array unit which is accessible from a plurality of host devices through a network device and from the power supply control device, at least two of the plurality of host devices operate with different power supply control specifications, in a power supply control step, and supplying electric power to the disk array unit and the power supply control device when the electric power supply from the first power supply device is disconnected in a second power supply steps, wherein the power supply control step comprises: collecting power supply fault information indicating a power supply failure of at least one of the plurality of host devices and the network device in a collecting step, wherein the power supply fault information is transferred according to a management control protocol which controls both the plurality of host devices and the network device; starting the supply of the electric power from the second power supply device when the electric power supplied from the first power supply device is disconnected in a starting step; and transmitting a notification to the disk array unit in response to the collection of the power supply fault information according to the management control protocol after starting the electric power supply from the second power supply device in a transmitting step, wherein the notification indicates that the electric power supplied from the first power supply device is disconnected. 
         [0017]    According to one aspect of the embodiments of the present invention, a power supply control device comprising: a power supply control means for controlling electric power supplied from a first power supply device to a disk array unit which is accessible from a plurality of host devices through a network device and from the power supply control device, at least two of the plurality of host devices operate with different power supply control specifications, and a second power supply device configured to supply electric power to the disk array unit and the power supply control device when the electric power supply from the first power supply device is disconnected, wherein the power supply control means comprises: a colleting means for collecting power supply fault information indicating a power supply failure of at least one of the plurality of host devices and the network device, wherein the power supply fault information is transferred according to a management control protocol which controls both the plurality of host devices and the network device; a starting means for starting the supply of the electric power from the second power supply device when the electric power supplied from the first power supply device is disconnected; and a transmitting means for transmitting a notification to the disk array unit in response to the collection of the power supply fault information according to the management control protocol after starting the electric power supply from the second power supply device, wherein the notification indicates that the electric power supplied from the first power supply device is disconnected. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Other features and advantages of various embodiments of the present invention will become apparent by the following detailed description and the accompanying drawings, wherein: 
           [0019]      FIG. 1  is a block diagram showing a configuration of a storage system of a first exemplary embodiment of the invention. 
           [0020]      FIG. 2  is a block diagram showing a configuration of a disk array unit  10  and an autonomous power supply control unit  11 . 
           [0021]      FIG. 3  is a flowchart showing a power supply control procedure of the autonomous power supply control unit  11  at the time of AC (Alternating Current) power supply disconnection. 
           [0022]      FIG. 4  is a flowchart showing a power supply control procedure of an array controller  21  at the time of AC supply disconnection. 
           [0023]      FIG. 5  is a block diagram showing a configuration of the disk array unit  10  and the autonomous power supply control unit  21  of the third exemplary embodiment of this invention. 
           [0024]      FIG. 6  is a flowchart showing a power supply control procedure when the power supply is controlled by the conventional power supply control mechanism in the forth exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    A first exemplary embodiment of the present invention will be described in detail below. 
       (1) First Exemplary Embodiment 
       [0026]      FIG. 1  is a block diagram showing a configuration of a storage system  1  of the first exemplary embodiment. In this embodiment, a disk array unit  10  has an independent unit for supplying electric power to the disk array unit  10 . 
         [0027]    The storage system  1  comprises the disk array unit  10 , an autonomous power supply control unit  11  (a power supply control device  11 ), a distribution board  12  (a first power supply  12 ), a plurality of host devices  14 , such as host computers, an operation management server  15 , and a network device  17 . 
         [0028]    The autonomous power supply control unit  11  is installed with simple network management protocol (SNMP) manager function, and operates as a SNMP manager. Moreover, the host device  14 , the operation management server  15  and the network device  17  operate as SNMP agents. 
         [0029]    The autonomous power supply control unit  11  is supplied with electric power from the distribution board  12  via a power cable  13 . The disk array unit  10  is supplied with electric power via the autonomous power supply control unit  11  and via a power cable  19 . 
         [0030]    The disk array unit  10 , the autonomous power supply control unit  11 , the host devices  14 , the operation management server  15  and the network device  17  are connected by a network for operation management  16 . Moreover, the disk array unit  10  and the autonomous power supply control unit  11  are connected by a storage area network (SAN) that includes, for example, the network device  17 . 
         [0031]    The disk array unit  10  and the autonomous power supply control unit  11  are connected by an interface  18 , and are enabled to communicate each other. 
         [0032]      FIG. 2  is a block diagram showing a configuration of the disk array unit  10  and the autonomous power supply control unit  11 . 
         [0033]    The disk array unit  10  is a device that comprises an array controller  21  (a first controller  21 ) and a disk enclosure  31 . Electric power for the array controller  21  is supplied from the distribution board  12  through the autonomous power supply control unit  11  and a power supply. Electric power for the disk enclosure  31  is supplied from the distribution board  12  through another power supply. 
         [0034]    The array controller  21  comprises an host interface  22 , a remote-controller communication part  23 , a host control unit such as a host control part  24 , a control unit such as a microprocessor  25 , a nonvolatile recording medium  26 , memory  27 , cache memory  28 , a recording medium  29 , a disk control unit such as a magnetic disk control part  30 , etc. Moreover, the disk enclosure  31  comprises a plurality of magnetic disks  32 . 
         [0035]    The remote-controller communication part  23  is connected with another array controller (not illustrated) in the disk array unit  10 . In this embodiment, the other array controller is referred to as a second controller. The second controller has a redundant structure to the first controller and can communicate with the first controller. 
         [0036]    The microprocessor  25  receives the data transmitted from the host device  14  and stores it in the cache memory  28  based on an I/O (Input/Output) command from the host device  14 , and subsequently stores the data in the magnetic disk  32 . Moreover, based on the I/O command from the host device  14 , the microprocessor  25  reads the corresponding data from the magnetic disk  32 , stores it in the cache memory  28 , and subsequently transmits the data to the host device  14 . 
         [0037]    The autonomous power supply control unit  11  comprises a power supply control unit such as a microprocessor  41 , a second power supply device such as a storage battery  42  or another type of electrical energy storage device such as a capacitor, a memory  43 , etc. 
         [0038]    The autonomous power supply control unit  11  is installed with an SNMP manager function, as described above. The autonomous power supply control unit  11  validates the SNMP manager function at the time when the SNMP manager starts to operate. Moreover, at the time of initialization, the autonomous power supply control unit  11  sets up network information for an SNMP agent group of the host devices  14 , the operation management server  15 , the network device  17 , etc. The autonomous power supply control unit  11  also makes a management table with the SNMP agent group network information. 
         [0039]    Next, the autonomous power supply control unit  11  processing when AC (Alternating Current) electric power from the distribution board  12  is disconnected will be explained with reference to the flowchart of  FIG. 3 .  FIG. 3  is a flowchart showing a power supply control procedure of the autonomous power supply control unit  11  at the time of AC power supply disconnection. 
         [0040]    Since the storage battery  42  is always supplied with electric power from the distribution board  12 , the microprocessor  41  monitors an electric power supply state of the distribution board  12  by communicating with the storage battery  42 . The microprocessor also monitors a supply state of AC electric power to the disk array unit  10  and the autonomous power supply control unit  11 . 
         [0041]    When the microprocessor  41  recognizes that the AC electric power supply from the distribution board  12  was disconnected by the monitoring described above (Step A 1 : YES), the storage battery  42  starts supplying electric power from the storage battery  42  to the disk array unit  10  and the autonomous power supply control unit  11  (Step A 2 ). 
         [0042]    Next, the microprocessor  41  determines whether or not a fault notification (SNMP Trap) was received from the SNMP agents such as the host device  14 , the operation management server  15  and the network device  17 . (Steps A 3 , A 4 ). 
         [0043]    Specifically, the microprocessor  41  determines whether the fault notification (SNMP Trap) was received from the host devices  14  and/or the operation management server  15  (Step A 3 ). Subsequently, when the fault notification is received from the host devices  14  and/or the operation management server  15  (Step A 3 : YES), the microprocessor  41  determines whether a link-down notification (the fault notification) was received from the network device  17  (Step A 4 ). 
         [0044]    In this way, in order to determine whether an AC electric power disconnection notification is to be transmitted to the array controller  21 , the microprocessor  41  determines simultaneously whether the microprocessor  41  has received the fault notification from the host devices  14  and/or the operation management server  15  and whether the microprocessor  41  has received the link-down notification (the fault notification) from the network device  17 . The following are the reasons. For example, it is difficult to detect a change of a link state of the network because the host device  14  sends a fault notification to the autonomous power supply control unit  11  when a fault occurs in the host device  14  alone. Also, when the host device  14  accesses the disk array unit  10  via the network device  17 , the host control part  24  cannot detect a change in the link state of the network. 
         [0045]    Next, when the link-down notification is received from the network device  17  (Step A 4 : YES), the microprocessor  41  proceeds to Step A 6 . 
         [0046]    On the other hand, if the microprocessor  41  does not receive the fault notification from all the SNMP agents that are management objects (Step A 3 : NO), or if the microprocessor  41  does not receive the notification of link-down from the network device  17  (Step A 4 : NO), the microprocessor  41  determines whether a specified time has elapsed after the AC electric power supply from the distribution board  12  is disconnected (Step A 5 ). 
         [0047]    That is, arrival of the fault notification is checked taking a specified wait time into consideration. This specified wait time is calculated based on power consumption of the disk array unit  10  and a capacity of the storage battery  42 , a capacity of the cache memory  28  of the disk array unit  10  and/or a data transfer rate from the cache memory  28  to the recording medium  29 , etc. The microprocessor  41  waits to receive the notification during the specified time (Step A 5 ). When the specified time has elapsed (Step A 5 : YES), the microprocessor  41  proceeds to Step A 6 . 
         [0048]    Next, the microprocessor  41  transmits the AC electric power disconnection notification to the array controller  21  through the interface  18  (Step A 6 ). 
         [0049]    Subsequently, the microprocessor  41  waits to receive a notification of electric power suspension of the storage battery  42  from the array controller  21  (Step A 7 ). After that, when the notification of electric power suspension of the storage battery  42  is received from the array controller  21  (Step A 7 : YES), the microprocessor  41  suspends the electric power supply from the storage battery  42  to the array controller (Step A 8 ). 
         [0050]    Next, processing by the array controller  21  after receiving the AC electric power disconnection notification will be explained with reference to the flowchart of  FIG. 4 .  FIG. 4  is a flowchart showing a power supply control procedure of an array controller  21  at the time of AC supply disconnection. 
         [0051]    If the AC electric power disconnection notification is received from the autonomous power supply control unit  11  (Step B 1 : YES), in the case of a redundant controller configuration, the microprocessor  25  checks whether the second controller also received the AC electric power disconnection notification through the remote-controller communication part  23  (Step B 2 ). 
         [0052]    Subsequently, if the second controller has not received the AC electric power disconnection notification (Step B 2 : NO), microprocessor  25  waits for the above specified time to elapse after the AC electric power supply from the distribution board  12  was disconnected (Step B 3 ). Then, when the specified time has elapsed (Step B 3 : YES), the microprocessor  25  determines that the other array controller operates normally, and issues the notification of electric power suspension of the storage battery  42  to the autonomous power supply control unit  11  in order to prevent wasted discharge of the storage battery  42  (Step B 4 ). 
         [0053]    When the specified time has elapsed, the autonomous power supply control unit  11  transmits the AC electric power disconnection notification (Step A 5 , A 6 ). Therefore, in the case where the second controller is connected to the control unit with a function equivalent to the autonomous power supply control unit  11 , if the AC electric power disconnection notification is not received even when the specified time has elapsed (Step B 2 , B 3 ), the microprocessor  25  determines that power supply of the second controller is not disconnected and the second controller is operating normally. 
         [0054]    On the other hand, if the second controller also received the AC electric power disconnection notification (Step B 2 : YES), the microprocessor  25  checks whether the host control part  24  of the array controller  21  received the I/O commands from the host devices  14  and whether or not all the I/O commands were processed (Step B 5 ). At this time, if the network device  17  is in a state of link-down, the I/O command corresponds to the I/O command that the host control part  24  received before the AC electric power disconnection and is being processed. 
         [0055]    Then, if all the I/O commands have not been processed in the host control part  24  of the array controller  21  (Step B 5 : NO), the microprocessor  25  waits until the specified time elapses after the AC electric power supply from the distribution board  12  was disconnected (Step B 6 ). Then, when the specified time has elapsed (Step B 6 : YES), the microprocessor  25  proceeds to Step B 7 . 
         [0056]    On the other hand, when all the I/O commands have been processed by the host control part  24  of the array controller  21  (Step B 5 : YES), the microprocessor  25  proceeds to Step B 7 . 
         [0057]    Next, in order to suppress discharge from the storage battery  42 , the microprocessor  25  disconnects power supplies of the host control part  24  and the magnetic disk control part  27 , and also suspends the electric power supply to the host control part  24  and the magnetic disk control part  27  (Step B 7 ). 
         [0058]    Subsequently, the microprocessor  25  starts writing the data in the cache memory  28  to the recording medium  29  (Step B 8 ). Then, when the writing of all the data in the cache memory  28  to the recording medium  29  has completed (Step B 9 : YES), the microprocessor  25  issues a notification of electric power suspension of the storage battery  42  to the autonomous power supply control unit  11  (Step B 10 ). 
         [0059]    Thereby, the microprocessor  25  can save the data in the cache memory  28  to the recording medium  29  quickly and safely while suppressing wasted discharge of the storage battery  42 . When the microprocessor  25  restarts the disk array unit  10  after the AC electric power supply from the distribution board  12  is restored, the microprocessor  25  can transmit the data in the recording medium  29  to the cache memory  28 , and resume the processing of the host devices  14 . 
         [0060]    In this way, in the storage system  1  of this embodiment, the SNMP manager function and the storage battery  42  are installed in the autonomous power supply control unit  11 . Also, the disk array unit  10  has recording medium  29 . Moreover, in the storage system  1 , the disk array unit  10 , the autonomous power supply control unit  11 , the host device  14 , the operation management server  15 , and the network device  17  are connected to the network  16  for operation management. Then, in the storage system  1 , the autonomous power supply control unit  11  functions as the SNMP manager. And the host device  14 , the operation management server  15 , and the network device  17  function as the SNMP agents. At the time of occurrence of power supply fault and at the time of occurrence of link-down, the SNMP agent notifies the SNMP manager of the fault. Then the SNMP manager performs power supply control based on the notification of fault. 
         [0061]    Therefore, it is possible for a plurality of host devices with different power supply control specifications to perform the power supply control of the disk array unit without being conscious of each company&#39;s own power supply control specification, and with minimum structure. 
         [0062]    Then, as explained above, the embodiment of the present invention has an effect as will be described below. The first effect is that in the disk array unit  10  in which a plurality of host devices  14  with different power supply control specifications are multi-platform connected, at the time of occurrence of a power failure, etc., the I/O commands from the host devices  14  are saved as data in the cache memory  29  for improving a writing response after I/O commands are processed as much as possible. The second effect is that it requires neither special-purpose software nor a special-purpose device, and processing of power supply disconnection is performed safely. 
         [0063]    Incidentally, the reasons why the autonomous power supply control unit  11  is independent are to achieve miniaturization of the array controller  21 , and to deal with the situation where the power supply control is not necessary because a constant voltage and constant frequency power supply (CVCF: Constant Voltage Constant Frequency) is installed in the disk array unit  10 . 
       (2) Second Exemplary Embodiment 
       [0064]    Although in the first exemplary embodiment, the autonomous power supply control unit  11  is independent, the configuration of the storage system  1  is not limited to this configuration. In the second exemplary embodiment, the autonomous power supply control unit  11  is incorporated in the disk array unit  10 . 
         [0065]    In this embodiment, the microprocessor  25  of the disk array unit  10  performs a processing ( FIG. 3 ) of the case where the AC electric power is disconnected from the aforementioned distribution board  12 . 
         [0066]    That is, when the electric power supply from the distribution board  12  is disconnected, the microprocessor  25  starts the electric power supply from the storage battery  42 . When the notification of fault was received from the host devices  14  and/or the network device  17 , the microprocessor  25  saves the data stored in the cache memory  28  to the recording medium  29  by the electric power supplied from the storage battery  42 . And when the saving of the data has completed, the microprocessor  25  suspends the electric power supply from the storage battery  42 . 
         [0067]    Therefore, the autonomous power supply control unit  11  becomes unnecessary, the interface  18 , the power cable  19 , the microprocessor  41 , and the memory  43  become unnecessary as a machine configuration. As a result, it is possible to reduce the number of the necessary device. 
       (3) The Third Exemplary Embodiment 
       [0068]    The embodiment of the present invention may be applied to an appliance NAS (Network Attached Storage) device. In the appliance NAS device, the host device  14  of  FIG. 1  is replaced with a NAS gateway or a NAS head. There are many configurations of the appliance NAS device where the host device  14  directly accesses the disk array unit  10  not through the network device  17 . 
         [0069]    In this case, the link-down of the host device  14  is detected by the host control part  24  of the array controller  21 . In the case where the disk array unit  10  and the autonomous power supply control unit  11  are independent, the link down is informed to the autonomous power supply control unit  11  via the network  16 . On the other hand, in the case where the autonomous power supply control unit  11  is incorporated in the disk array unit  10 , all processing are performed in the array controller  21 . Incidentally, a processing ( FIG. 3 ) of a case where the AC electric power is disconnected from the distribution board  12  and a processing ( FIG. 4 ) of the array controller  21  after receiving the notification of AC electric power disconnection are performed similarly with the first exemplary embodiment. 
       (4) The Forth Exemplary Embodiment 
       [0070]    In the forth exemplary embodiment, the conventional original power supply control specification is incorporated in the storage system  1  of the first exemplary embodiment. 
         [0071]      FIG. 5  is a block diagram showing a configuration of the disk array unit  10  and the autonomous power supply control unit  21  of the forth exemplary embodiment of this invention. In this case, the storage system  1  is the same as the configuration of the storage system  1  of  FIG. 2  except that the conventional power supply control mechanism  45  is connected to a legacy I/F in (LEGACY I/F IN)  44  of the autonomous power supply control unit  11 . 
         [0072]    Next, the power supply control method of this embodiment is explained with regard to a flowchart of  FIG. 6 . First, the autonomous power supply control unit  11  determines whether the conventional power supply control mechanism  45  is incorporated or not (Step C 1 ). Subsequently, in the case where the conventional power supply control mechanism  45  is incorporated (Step C 1 : YES), the autonomous power supply control unit  11  invalidates the SNMP manager function (Step C 2 ), and activates a control task for performing communication with the conventional power supply control mechanism  45  (Step C 3 ). 
         [0073]    Subsequently, the autonomous power supply control unit  11  determines whether the command was received from the conventional power supply control mechanism  45  (Step C 4 ), if the command was received (Step C 4 : YES), the autonomous power supply control unit  11  will analyze contents of the command (Step C 5 ), and will transmit power supply control information based on the analysis result to the array controller  21  (Step C 6 ). 
         [0074]    For example, if the command from the conventional power supply control mechanism  45  is an AC electric power disconnection command indicating that electric power from the distribution board  12  is disconnected, the autonomous power supply control unit  11  transmits to the array controller  21  the power supply control information corresponding to the notification of AC electric power disconnection. 
         [0075]    Thereby, also in the storage system which has the conventional original power supply control specification, the autonomous power supply control unit  11  can perform the power supply control. Thus, in the storage system  1 , the legacy I/F in  44  is incorporated in the autonomous power supply control unit  11  in order to connect with the conventional power supply control mechanism  45 . As a result, it is possible for the autonomous power supply control unit  11  to interpret a command of the original mechanism  45  whose specification is disclosed and to perform the power supply control. 
         [0076]    The embodiments of the present invention are usable not only in the disk array unit  10  but also in electric power control of a host-SAN switch-disk array unit in a data storage dedicated network (FC-SAN, IP-SAN), an NAS device for a file server, and whole peripheral devices connected to the host devices. 
         [0077]    While the embodiments of this invention have been described in conjunction with the preferred embodiments described above, it will now be possible for those skilled in the art to put this invention into practice in various other manners.