Abstract:
A storage apparatus includes: a storage medium for storing data; a controller for controlling an access from an upper device to the storage medium through a data line for transmitting data; a detector for detecting a transition of an access signal for requesting access from the upper device through the data line; and a power controller for supplying power to the controller in accordance with a rate of the transition of the access signal detected by the detector.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2009-244726 filed on Oct. 23, 2009, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The embodiments discussed herein are related to a storage apparatus. 
       BACKGROUND 
       [0003]    It is known as to a system in which a plurality of data processing devices are connected to one another that one of the data processing devices activates another one of the data processing devices. As an exemplary system in which a plurality of data processing devices are connected to one another, there is a storage apparatus including a primary device which controls an access request from the outside and an extended device which controls an access request from the primary device to a storage medium included in the own device connected to each other. 
         [0004]    A storage apparatus including a primary device connected with an extended device can be provided with more extended devices so that storage media can be added to the storage apparatus. The extended device is, e.g., connected in series to the primary device. The storage apparatus including the primary device connected with the extended device can be configured in such a way that the primary device can activate the extended device. 
         [0005]    In order that the primary device is configured to activate the extended device, an exclusive line for power supply control can be provided between the primary device and the extended device. Further, the extended device can be provided in itself with a controller connected to the primary device and configured to control an access to a storage medium provided in the own device, and the controller can be configured to work all the time and to activate the storage medium on the basis of communication with the primary device. Incidentally, if extended devices are connected in series, one of the extended devices having been activated can activate another one of the extended devices connected downstream, so that the plural extended devices can be successively activated. Japanese Laid-open Patent Publication Nos. 59-37755, 2000-214964 and No. 2003-8592 are examples of related art. 
         [0006]    The communication interface between the primary device and the extended device, however, may lack a signal for power supply control in some cases. If the communication interface lacking a signal for power supply control is used, a configuration such that an exclusive line for power supply control is provided between the primary device and the extended device as described above cannot be employed. 
         [0007]    Further, according to the configuration such that the extended device is provided in itself with a controller connected to the primary device by means of communication and configured to control an access to a storage medium provided in the own device, and that the controller is configured to work all the time, power consumption required by the controller to work cannot be disregarded. 
         [0008]    As described above, there is ordinarily a problem in that a communication interface lacking a signal for power supply control cannot reduce the power consumption enough in a waiting state. 
       SUMMARY 
       [0009]    According to an aspect of the embodiment, a storage apparatus includes: a storage medium for storing data; a controller for controlling an access from an upper device to the storage medium through a data line for transmitting data; a detector for detecting a transition of an access signal for requesting access from the upper device through the data line; and a power controller for supplying power to the controller in accordance with a rate of the transition of the access signal detected by the detector. 
         [0010]    The object and advantages of the embodiment will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0011]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1  is a block diagram for illustrating a configuration of a storage apparatus according to a first embodiment; 
           [0013]      FIG. 2  is a block diagram for explaining a configuration of a storage apparatus according to a second embodiment; 
           [0014]      FIG. 3  is a block diagram for illustrating a configuration of an example to be compared with; 
           [0015]      FIG. 4  explains a method for OOB detection by means of observing a voltage level; 
           [0016]      FIG. 5  explains a method for OOB detection by means of frequency analysis; 
           [0017]      FIG. 6  is a flowchart for explaining a processing operation performed when the extended device is activated; 
           [0018]      FIG. 7  explains a waiting state of the extended device; 
           [0019]      FIG. 8  explains a state in which the extended device detects an OOB sequence; 
           [0020]      FIG. 9  explains a state in which the extended device is in operation; and 
           [0021]      FIG. 10  is a sequence diagram for explaining power-on synchronization in the storage apparatus. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0022]    Embodiments of a storage apparatus disclosed by the present application will be explained in detail with reference to the drawings below. Incidentally, the embodiments do not limit the scope of the disclosed art. 
       First Embodiment 
       [0023]      FIG. 1  is a block diagram for illustrating a configuration of a storage apparatus according to a first embodiment. The storage apparatus  10  illustrated in  FIG. 1  has an upper communication line  20   a  via which the storage apparatus  10  is connected to and communicates with an upper device, a system controller  21 , an OOB (Out Of Band) detector  23 , a power supply controller  24  and a storage medium  27 . 
         [0024]    The storage medium  27  stores data. The storage medium  27  is a storage medium of any type such as a magnetic disk (HDD: Hard Disk Drive) or a semiconductor recording medium (SSD: Solid State Drive). The upper communication line  20   a  is a communication line for connecting the storage apparatus  10  to the upper device. The upper device is any device which accesses the storage medium  27  of the storage apparatus  10  via the upper communication line  20   a.    
         [0025]    The system controller  21  is a controller which controls an access request to the storage medium received via the upper communication line  20   a . The system controller  21  is supplied with no power and does not work while the storage apparatus  10  is in a waiting state. 
         [0026]    The upper device sets up a communication session by using an OOB (Out Of Band) sequence, etc. before starting an operation for connecting with the storage apparatus  10 . The OOB detector  23  observes the upper communication line  20   a . Upon detecting a rising edge of a signal used for the OOB sequence, the OOB detector  23  notifies the power supply controller  24  of the detection. The OOB detector  23  is supplied with power even while the storage apparatus  10  is in the waiting state. The OOB detector  23  thereby enables a detecting operation even while the storage apparatus  10  is in the waiting state. 
         [0027]    Upon receiving the notice from the OOB detector  23 , the power supply controller  24  powers on and activates the system controller  21 . As being supplied with power even while the storage apparatus  10  is in the waiting state, the power supply controller  24  enables an operation to wait for a notice coming from the OOB detector  23 . 
         [0028]    As described above, the storage apparatus according to the first embodiment leaves the system controller  21  not working in the waiting state, detects a rising edge of a signal received from the upper device by means of the OOB detector  23  and activates the system controller  21 . The storage apparatus can thereby implement power-on synchronization among the devices while reducing power consumption in the waiting state without using a signal for power supply control. 
       Second Embodiment 
       [0029]      FIG. 2  is a block diagram for explaining a configuration of a storage apparatus according to a second embodiment. As illustrated in  FIG. 2 , the storage apparatus  1  of the second embodiment has a primary device  11  and extended devices  12  and  13 . 
         [0030]    The primary device  11  is a control enclosure which controls an access request coming from an external server  2 . The extended device  12  is connected with the primary device  11  and is a storage apparatus which controls an access request coming from the primary device to a storage medium provided in the own device, i.e., a disk enclosure, and so is the extended device  13 . 
         [0031]    The extended devices  12  and  13  are connected in series with the primary device  11 . For communication between the primary device  11  and the extended device  12  and between the extended devices  12  and  13 , a SAS (Serial Attached SCSI) interface is used.  FIG. 2  illustrates a configuration such that the extended devices  12  and  13  are connected in series with the primary device  11 , and a plurality of extended devices can further be connected in series at later stages of the extended device  13 . 
         [0032]    The extended device  12  has an upper communication line  20   a , a lower communication line  20   b , a system controller  21 , an OOB detector  23 , a power supply controller  24 , a DC power producing device  25 , a synchronizing function changeover switch  26  and storage media  27 - 1  through  27 - n.    
         [0033]    The system controller (SASexpander)  21  controls data communication among the primary device  11  being an upper device, the storage media  27 - 1  through  27 - n  and the extended device  13  being a lower device. The upper communication line  20   a  which connects the primary device  11  and the system controller  21  has, e.g., four signal lines. The lower communication line  20   b  which connects the system controller  21  and the extended device  13  similarly has, e.g., four signal lines. 
         [0034]    The system controller  21  is a logic device of any kind. The system controller  21  runs a system control firm  22  on the device. The system controller  21  can be, e.g., a device having a CPU (Central Processing Unit) and a memory. The system controller  21  carries out a process for communication with the primary device  11  and with the extended device  13 , and a process for accessing the storage media  27 - 1  through  27 - n  by running the system control firm  22 . Upon being supplied with no power in a waiting state of the extended device  12 , the system controller  21  does not work. 
         [0035]    The synchronizing function changeover switch  26  holds data indicating whether the extended device  12  is activated synchronously with the primary device  11  having been activated. The synchronizing function changeover switch  26  provides the OOB detector  23  with a signal corresponding to the data being held. If the synchronizing function changeover switch  26  is turned on, the extended device  12  in a waiting state is activated synchronously with the primary device  11  having been activated. After being activated, the extended device  12  is ready to ordinarily operate, i.e., ready to access the storage media  27 - 1  through  27 - n . Meanwhile, if the synchronizing function changeover switch  26  is turned off, the extended device  12  is activated asynchronously with the primary device having been activated upon being directly operated by an operator. 
         [0036]    The OOB detector  23  observes the upper communication line  20   a . The OOB detector  23  detects a rising edge of a signal used for an OOB sequence. The OOB detector  23  is supplied with power so as to be ready to work even in the waiting state of the extended device  12 . If the synchronizing function changeover switch  26  is turned on, the OOB detector  23  detects a rising edge of a signal. If the synchronizing function changeover switch  26  is turned off, the OOB detector  23  does not detect a rising edge of a signal. If the OOB detector  23  does not detect a rising edge of a signal, the OOB detector  23  can be supplied with no power, or can refrain from working while being supplied with power. 
         [0037]    If the OOB detector  23  detects a rising edge of a signal, the power supply controller  24  controls the DC power producing device  25  so as to power on and activate the system controller  21  and the storage media  27 - 1  through  27 - n . After activating the system controller  21 , the power supply controller  24  makes the OOB detector  23  stop working. As the OOB detector  23  stops working, the storage apparatus can reduce power consumption after starting to work. 
         [0038]    The DC power producing device  25  adjusts an output level of voltage provided by an apparatus power supply in response to control directions coming from the power supply controller  24 . The DC power producing device  25  supplies the system controller  21  and the storage media  27 - 1  through  27 - n  with the adjusted voltage. 
         [0039]    As described above, the extended device  12  leaves the system controller  21  not working in the waiting state. Then, upon detecting a rising edge of a signal received from the upper device by means of the OOB detector  23 , the extended device  12  activates the system controller  21 . The storage apparatus of the embodiment can thereby reduce power consumption without using a signal for power supply control. Further, as explained below, the storage apparatus according to the embodiment can consume less power than a configuration such that the system controller works in the waiting state and detects a signal. 
         [0040]    A storage apparatus configured to work the system controller in a waiting state and to detect a signal will be explained below as an example to be compared with.  FIG. 3  is a block diagram of the storage apparatus for illustrating the configuration of the example to be compared with. The storage apparatus  3  illustrated in  FIG. 3  has a primary device  31  and extended devices  32  and  33 . The primary device  31  and the extended devices  32  and  33  are connected in series with one another. 
         [0041]    The extended device  32  has an upper communication line  20   a , a lower communication line  20   b , a system controller  41 , a power supply controller  44 , a DC power producing device  45 , a synchronizing function changeover switch  46  and storage media  47 - 1  through  47 - n.    
         [0042]    The system controller  41  communicates with the primary device  31  and the extended device  33  by running a system control firm  42 . The system controller  41  processes access to the storage media  47 - 1  through  47 - n . The system controller  41  has an OOB detector  43 . The OOB detector  43  is, e.g., a program to be run by the system controller  41 . 
         [0043]    The system controller  41  is supplied with power and works even in a waiting state of the extended device  32 . The system controller  41  observes the upper communication line  20   a  by means of the OOB detector  43 . Upon receiving a signal related to the OOB sequence, the OOB detector  43  activates the system control firm  42 . 
         [0044]    The synchronizing function changeover switch  46  holds data indicating whether the extended device  32  is activated synchronously with the primary device  31  having been activated. The synchronizing function changeover switch  46  provides the system controller  41  with a signal corresponding to the data being held. If the synchronizing function changeover switch  46  is turned on, the system controller  41  detects a rising edge of the signal by means of the OOB detector  43 . If the synchronizing function changeover switch  46  is turned off, the system controller  41  does not detect a rising edge of the signal by means of the OOB detector  43 . 
         [0045]    Upon receiving instructions from the system controller  41  having detected a signal by means of the OOB detector  43 , the power supply controller  44  powers on and activates the storage media  47 - 1  through  47 - n  by controlling the DC power producing device  45 . 
         [0046]    The DC power producing device  45  adjusts an output level of voltage provided by an apparatus power supply in response to control directions coming from the power supply controller  44 . The DC power producing device  45  supplies the storage media  47 - 1  through  47 - n  with the adjusted voltage. 
         [0047]    As described above, the extended device  32  illustrated as the example to be compared with is activated synchronously with the primary device  31 . That is, the system controller  41  works even in the waiting state of the extended device  32 . Thus, the extended device  32  consumes more power in the waiting state than the extended device  12  illustrated in  FIG. 2 . 
         [0048]    Return to the explanation with reference to  FIG. 2 . An operation of the OOB detector  23  illustrated in  FIG. 2  will be explained as follows. In the OOB sequence, one device transmits to the outside a COMINIT signal for checking whether a device to communicate with is present. Another device having received the COMINIT signal transmits a COMINIT signal back. The two devices having transmitted and received the COMINIT signals to and from each other successively transmits and receives signals such as COMSAS and COMWAKE for identifying a communication type. 
         [0049]    The OOB detector  23  detects the COMINIT signal. The COMINIT signal has a voltage signal waveform having six peaks during 106.67 ns. The OOB detector  23  detects the voltage signal waveform of the COMINIT signal. To put it specifically, the OOB detector  23  can observe a voltage level on the upper communication line  20   a , or can analyze a frequency of a signal on the upper communication line  20   a.    
         [0050]      FIG. 4  illustrates a method for OOB detection by means of observing the voltage level. The OOB detector  23  sets “1” to a register if a voltage of a signal propagated on the upper communication line  20   a  exceeds a threshold, and resets the register if the register is read. As an observation interval is made much shorter than 106.67 ns, the OOB detector  23  can detect the COMINIT signal.  FIG. 4  specifically illustrates an exemplary case in which the observation interval of the register is made 30 ns. If the observation interval of the register is 30 ns, the OOB detector  23  identifies success in the OOB detection if values of the register having been read are “1” consecutively three times. Although success in the OOB detection is identified if values of the register having been read are “1” consecutively three times for the example illustrated here, the number of times is not limited to three and any number of times can be suitably chosen. 
         [0051]      FIG. 5  illustrates a method for OOB detection by means of frequency analysis. The OOB detector  23  performs the OOB detection depending upon how many times rising edges of a voltage signal are detected in a lapse of 106.67 ns after the voltage of the signal propagated on the upper communication line  20   a  exceeds a threshold. The OOB detector  23  identifies success in the OOB detection if the rising edges of the voltage signal are detected five times in a lapse of 106.67 ns after the voltage of the signal exceeds the threshold. Although the OOB detector  23  identifies success in the OOB detection if the rising edges of the voltage signal are detected five times for the example illustrated here, the number of times is not limited to five and any number of times can be suitably chosen. 
         [0052]    Then, a processing operation performed when the extended device  12  is activated will be explained.  FIG. 6  is a flowchart for illustrating the processing operation performed when the extended device  12  is activated. Further,  FIGS. 7-9  illustrate a change of the extended device  12  from a waiting state to an operating state. 
         [0053]    In the waiting state of the extended device  12 , the OOB detector  23  observes voltage of an input signal propagated on the upper communication line  20   a  ( FIG. 6 , S 101 ).  FIG. 7  explains the waiting state of the extended device  12 . In  FIG. 7 , components being powered on and working are illustrated by solid frames, and components not working are illustrated by dotted frames. In the waiting state of the extended device  12 , the OOB detector  23  and the power supply controller  24  are working, and so are neither the system controller  21  nor the storage media  27 - 1  through  27 - n . Further, the primary device  11  has started to work in  FIG. 7 . 
         [0054]    The primary device  11  carries out the OOB sequence upon being activated, and transmits a COMINIT signal to the upper communication line  20   a  which connects the extended device and the primary device as illustrated in  FIG. 8 . In  FIG. 8 , components being powered on and working are illustrated by solid frames, and components not working are illustrated by dotted frames. Upon detecting the COMINIT signal ( FIG. 6 , S 102 , Yes), the OOB detector  23  notifies the power supply controller  24  of the detection ( FIG. 6 , S 103 ). 
         [0055]    Upon being notified by the OOB detector  23 , the power supply controller  24  powers on the system controller  21 , and directs the system controller  21  to activate the system control firm  22 . Upon being directed, the system control firm  22  starts to be activated ( FIG. 6 , S 104 ), and starts to transmit a COMINIT signal to the lower device (S 105 ). The power supply controller  24  stops the OOB detector  23  (S 106 ). 
         [0056]      FIG. 9  illustrates the extended device  12  in the operating state. In  FIG. 9 , components being powered on and working are illustrated by solid frames, and components not working are illustrated by dotted frames. In the operating state, the DC power producing device  25  is activated by the power supply controller  24  and supplies the system controller  21  and the storage media  27 - 1  through  27 - n  with power. 
         [0057]    The system controller  21  works upon being supplied with power. The system controller  21  runs the system control firm  22 . The system control firm  22  starts the OOB sequence, and transmits a COMINIT signal to the lower communication line  20   b.    
         [0058]    Thus, if the extended device  13  being the lower device is configured similarly as the extended device  12 , the extended device  13  can detect the COMINIT signal transmitted by the extended device  12  and be activated from the waiting state. 
         [0059]      FIG. 10  is a sequence diagram for illustrating power-on synchronization in the storage apparatus  1 . The primary device  11  and the extended devices  12  and  13  are waiting in an initial state. The primary device  11  is activated at first as operated by an operator, etc. (S 201 ), and starts the OOB sequence (S 202 ). In the OOB sequence, the primary device  11  transmits a COMINIT signal to the extended device  12 . The primary device  11  transmits COMINIT signals repeatedly until the primary device receives a COMINIT signal from the extended device  12 . 
         [0060]    The extended device  12  detects the COMINIT signal by means of the OOB detector  23  (S 211 ), and activates the own device (S 212 ). After being activated, the extended device  12  starts the OOB sequence (S 213 ), and starts to transmit COMINIT signals to the primary device  11  and to the extended device  13 . 
         [0061]    Upon receiving the COMINIT signal from the extended device  12 , the primary device  11  can shift to a next step in the OOB sequence. Further, upon receiving the COMINIT signal from the extended device  12 , the extended device  13  can start to activate the own device. 
         [0062]    According the storage apparatus  1  of the second embodiment, as described above, the extended device  12  leaves the system controller  21  not working in the waiting state, and observes the upper communication line  20   a  by means of the OOB detector  23 . Upon detecting a COMINIT signal transmitted by the primary device  11 , the OOB detector  23  notifies the power supply controller  24  of the detection so as to activate the system controller  21 . The storage apparatus  1  can thereby use a sequence for starting the SAS communication so as to activate the extended device  12  synchronously with the primary device  11  having been activated. 
         [0063]    Further, the storage apparatus  1  observes the OOB sequence of the primary device  11  by means of the OOB detector  23  consuming less working power than the system controller  21 . The storage apparatus  1  can thereby consume less power than a configuration such that the system controller  21  works in the waiting state so as to implement power-on synchronization. 
         [0064]    Further, the extended device carries out the OOB sequence and transmits a COMINIT signal to the lower device when being activated. The storage apparatus  1  can thereby implement the power-on synchronization for the extended device  13  connected in series to the extended device  12  and for the following lower devices, as well. 
         [0065]    Further, the extended device  12  can prevent the power consumption for working from increasing by stopping the operation of the OOB detector  23  after being activated. Incidentally, in order that the operation of the OOB detector  23  is stopped, the OOB detector  23  can be supplied with no power, or can stop the operation for observation while being supplied with power. The OOB detector  23  stops the operation after being activated, and then resumes the operation upon the extended device  12  falling in a waiting state next time.