Abstract:
A CPU determines whether the intended use of the image data to be stored in a plurality of HDDs has a first-type purpose, which requires storing temporarily stored image data for carrying out output processing of the image data, or a second-type purpose, which requires long-term preservation of the image data. If the first-type intended use is determined, a first-type mode for saving is selected, wherein the image data to be stored are divided and each divided set of image data is stored into one HDD. If the second-type intended use is determined, a second-type mode for saving is selected, wherein the same image data part is saved in a plurality of storage means.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention generally relates to an image data storage system or apparatus that has a plurality of storage means for storing the image data. More specifically, the present invention relates to such an image data storage system or apparatus that has a plurality of storage means for storing the image data to be used in a digital copying machine.  
           [0003]    2. Description of the Related Art  
           [0004]    As one of today&#39;s known digital copiers, there is a digital copier that has a hard disk drive (hereinafter referred to as HDD) as a means for storing image data. A HDD as such has been utilized for a function that stores the image data once and then uses the data, e.g., an electronic sorting function, an image registration function, etc. In the electronic sorting function, original image data are obtained by scanning a plurality of pages or sheets, then the obtained original image data sets are stored into a HDD and thereafter each image data set in the order of its corresponding page number is read out from the HDD for the purpose of making printouts. This function enables delivery of sorted copier-paper printouts without a more-conventional, sorting-hardware mechanism, which has a plurality of sorting bins. On the other hand, in the image registration function, a plurality of form images (sets) as the registration images are stored into the HDD and thereafter printouts can be made on an on-demand basis, eliminating the necessity of a scanning process that would otherwise be required each time when additional copies are made.  
           [0005]    Nowadays, we have seen the necessity of using a plurality of HDDs in parallel for storing the image data in order to keep up with the requirements of higher speeds in print-out performance while using the electronic sorting function, not to speak of the requirements of high speeds due to the increases in amount of information to be handled, which come from recent years preferences for high resolution images. For instance, an A4-sized and 1,200-dpi image amounts to about 17 MByte of data, when each pixel is considered to occupy 1 bit. If a print-out performance of 120 pages per minute are required, the required data transfer rate of the HDD would be about 34 MBytes per second, as is obtained by the calculation of: (17 MBytes×120)/60 sec.=34 MBytes/sec. However, at present, a typical data transfer rate of a reasonable HDD is about 20 MBytes/sec., which is unable to satisfy the above data transfer rate requirement of 34 Mbytes per sec. Thus, in order to satisfy the above print-out speed requirement, two HDDs simultaneously operated in parallel are utilized, which achieves a data transfer rate of about 40 Mbytes per sec. There is another approach to improve the data access speed without the use of a plurality of HDDs: Japanese unexamined patent publication (KOKAI) No. 2000-32243 shows a copier apparatus utilizing a HDD, with a consideration of data access rates which vary depending on various storage areas of the HD (hard disk), which seems to be able to temporarily improve the data access speed of the same HD.  
           [0006]    On the other hand, registered document-form images or those in conjunction with the image registration function that are preserved as stored data in a hard disk tend to be utilized a number of times. Therefore, what is important is the reliability, i.e., the prevention of loss of correct data due to malfunctions, etc., rather than the print-out speeds. In this respect, the aforementioned Japanese unexamined patent publication (KOKAI) No. 2000-32243 does not seem to teach any reliability considerations on its preserved data in its HDD.  
         SUMMARY OF THE INVENTION  
         [0007]    It is therefore a first object of the present invention to provide an image data storage system having a plurality of image data storage means, which satisfies both the requirements of the high speed transfer of the image data and of the data reliability.  
           [0008]    A second object of the present invention is to make a choice based on the intended use of the image data that are to be stored in HDDs, the choice being made so that the image data are divided and stored into a plurality of HDDs, each having a divided piece of the image data and/or the image data is stored in a plurality of HDDs, each having the same data. Thus, as for data that require a high access rate of HDDs, high, access rate is made possible, and as for data of which its preservation is important, the same data can be output from another HDD even if one HDD fails to operate properly. Consequently, the HDDs are controlled to store data in accordance with the intended use of the data.  
           [0009]    A third object of the present invention is to make a choice between data so as not to use data in a HDD if there is a data abnormality in said HDD, when the data stored by a storing mode of storing identical data into a plurality of storage means is read out, thereby preventing the adverse effect that can occur due to data abnormality caused by a HDD that has failed to operate properly.  
           [0010]    A fourth object of the present invention is to identify or pinpoint a HDD that has an abnormality in an image data storage system utilizing a plurality of HDDs, thereby providing a clear-cut notice to its user.  
           [0011]    A fifth object of the present invention is to arrange so that when a HDD (in a system which utilizes the mode of storing identical data in a plurality of HDDs) is replaced due to its malfunction, etc., the data that is stored for intended long time preservation and use is transferred from one of the other HDDs and is stored into a replacement HDD, thereby sustaining data maintainability, in order to enhance the maintainability of data stored with intended long-term preservation and use.  
           [0012]    The objects of the present invention can be achieved based on an image data storage system or apparatus, comprising:  
           [0013]    a plurality of storage means for storing image data;  
           [0014]    means for determining intended use of the image data that is stored at said image data storage means;  
           [0015]    selection means for selecting a given type of image storing mode for storing said image data into one of said storage means, wherein the selection is performed based on the determined intended use of image data; and  
           [0016]    data saving means for saving said image data into at least one of said plurality of said storage means in accordance with the image storing mode selected by said selection means.  
           [0017]    In the above system, it is preferable that said selection means select one of:  
           [0018]    a first storage mode for storing image data divided into sets of data, each of said sets of data being respectively stored into a corresponding one of said plurality of said storage means; and  
           [0019]    a second storage mode for storing image data into at least two of said plurality of storage means, each of said at least two storage means storing an identical part of said image data.  
           [0020]    Further, in the above system, it is also preferable that said intended use of said image data includes a first intended use and a second intended use, wherein said first intended use is to temporarily store said image data for a time period of output process of said image data and said second intended use is to store said image data for long-term preservation of said image data, and wherein said selection means selects said first mode when said intended use is said first intended use and selects said second mode when said intended use is said second intended use.  
           [0021]    In any one of the above systems, it is also preferable that said determining means determine said intended use in accordance with information provided through input means operated by a user.  
           [0022]    In any one of the above systems, it would be also preferable to further arrange so that data other than image data are stored by said second storage mode.  
           [0023]    In any one of the above systems, it would be also preferable to further arrange so that when the data stored by said second mode are read out, each data part is read out from each of said at least two of said plurality of storage means, and determination is made on whether said data part read out from one of said plurality of storage means is abnormal data so as to select and output said data part read out from one of said image data storage means other than the abnormal data.  
           [0024]    Further, in the above system, it would be also preferable for said system to display a notice with respect to said image data storage means in which said abnormal data has occurred.  
           [0025]    In any one of the above systems, it would be also preferable to further arrange so that when the system is initialized and if a certain image data storage means that lacks a history of usage has been detected based on histories of usage in said plurality of storage means, the data stored by said second mode in one of said storage means that has usage history is duplicated into said image data storage means that lacks said history of usage.  
           [0026]    In any one of the above image data storage systems, HDDs can be employed as the plurality of the image data storage means.  
           [0027]    Any one of the above image data storage systems are useful, for example, when provided in an image formation apparatus such as a copier, a printer or a fax machine.  
           [0028]    Other features that may be employed to help further achieve the objects together with the advantageous effects of the present invention will become apparent by reference to the following detailed description when considered in connection with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]    [0029]FIG. 1 is a schematic illustration of a copier showing an example of an image data storage system of the present invention;  
         [0030]    [0030]FIG. 2 is a block diagram showing the overview of the control system section of the copier shown in FIG. 1;  
         [0031]    [0031]FIG. 3 is a block diagram showing a HDD array controller IC of a HDD control section shown in FIG. 2;  
         [0032]    [0032]FIG. 4 is a diagram in explanation of an example of a register configuration for HDD I/Fs (HDD interfaces) A-D ( 303 - 306 ) shown in FIG. 3;  
         [0033]    [0033]FIG. 5 is a diagram in explanation of an example of a detailed internal construction of one of the HDD I/Fs A-D ( 303 - 306 ) shown in FIG. 3;  
         [0034]    [0034]FIG. 6 is a timing chart of main signals that occur when a state machine (shown in FIG. 5) in one of the HDD I/Fs A-D ( 303 - 306 ) shown in FIG. 3 is in its HDD-writing operation;  
         [0035]    [0035]FIG. 7 is a timing chart of main signals that occur when the state machine (shown in FIG. 5) is in its HDD-reading operation;  
         [0036]    [0036]FIG. 8 is a diagram in explanation of an example of a DMA transfer scheme of the HDD I/Fs A-D ( 303 - 306 ) shown in FIG. 3;  
         [0037]    [0037]FIG. 9 is a diagram in detailed explanation of an example of how the data are divided and stored in the HDDs;  
         [0038]    [0038]FIG. 10 is a schematic explanation of how the data are divided and stored in the HDDs when all the HDD I/Fs A-D have been asserting REQ signals and the data are being divided prior to being stored into the HDDs;  
         [0039]    [0039]FIG. 11 is a schematic explanation of how the data are divided and stored in the HDDs when all the HDD I/Fs A-D have been asserting REQ signals and the data are still being divided while the HDDs are storing the data;  
         [0040]    [0040]FIG. 12 is a diagram in schematic explanation of how the data are divided and stored in the HDDs when the HDD I/Fs A-D have negated REQ signals and yet the HDDs are storing the divided portions of the data;  
         [0041]    [0041]FIG. 13 is a diagram in detailed explanation of an example of a different layout of transferred data in a different-type mode, i.e., when the same data are commonly stored in each of the four HDDs, in the same system of FIG. 9;  
         [0042]    [0042]FIG. 14 is a detailed view of a user operation panel of the copier of the embodiment of the present invention;  
         [0043]    [0043]FIG. 15 is a flow chart of the document registration process of the present invention;  
         [0044]    [0044]FIG. 16 is a detailed view of a registered-document-list/document-registration-setting window that appears in a LCD of the user operation panel of FIG. 14;  
         [0045]    [0045]FIG. 17 is a flow chart of the registered document print out process of the present invention;  
         [0046]    [0046]FIG. 18 is a block diagram showing in detail an abnormal data detection process section, which is located within the CPU/DMA I/F (CPU/DMA interface)  302  of FIG. 3;  
         [0047]    [0047]FIG. 19 is a detailed view of a malfunction notice window, which appears in the LCD of the user operation panel of FIG. 14; and  
         [0048]    [0048]FIG. 20 is a flow chart of a new HDD detection process and its related data copying process of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0049]    According to the general principle of the present invention, a plurality of HDDs are utilized. The data storing format in these HDDs can be varied in response to an intended use of the incoming image data, in such a manner that a data storing mode that is suitable for the intended use, in view of speeds and data maintainability, etc., is selected. Embodiments of the present invention are described below.  
         [0050]    [0050]FIG. 1 is a schematic illustration of a digital copier, which relates to an embodiment of the present invention. In this copier, a scanner section  101  and a laser-recorder section  102  perform image formation and printing onto the paper. A tail end process section  103  jogs output papers, staples them, punches them, etc. The scanner section  101  includes an original document table or original glass plate  104  made of clear glass, a reversing automatic document feeder (hereinafter referred to as RADF)  105  that feeds an original copy along the upper surface of the glass plate  104 , and a scanner unit  106  that obtains image data by scanning the original copy during its stay on the upper surface of the glass plate  104 .  
         [0051]    The RADF  105  has a first path for feeding of single-sided original copies and a second path for feeding of double-sided original copies in order to handle both types of original copies. The first path extends from an original receiving tray (not shown), via the original glass plate  104 , to an outlet tray (not shown). As for a double-sided original copy, when the original copy has been scanned by the scanner unit  106 , it is reversed and guided again onto the original glass plate in the second path. The scanner unit  106  illuminates the original copy with a lamp. The scanner unit  106  arranges that the reflected light from the original copy is focused with a lens, a mirror, etc., in order to obtain imaging on an acceptance surface of photoelectric conversion element. The photoelectric conversion element obtains an electrical signal by converting the incoming reflected light and outputting the electric signal into an image processing section, which will be described later.  
         [0052]    The image data obtained by the scanner section  101  is output into the laser-recorder section  102 . The laser-recorder section includes a paper feed section  107  for feeding paper, a laser-writing (or laser write) unit  108  and a electrophotographic processing section  109 . The paper feed section  107  has a secondary paper-feed path which, in a double-sided copying mode, reverses or turns over the faces of, and guides into the electrophotographic processing section  109  again, the copier paper that has passed the fixing roller.  
         [0053]    The laser write unit  108  has a semiconductor laser that radiates laser light based on the image data provided from the image processing section. The light radiated from the semiconductor laser is directed to achieve light distribution onto the surface of a photosensitive drum of the electro-photographic processing section  109  via a mirror and a lens. An electrostatic latent image is formed on the surface of the photosensitive drum. With the toner supplied from an image development or photofinishing unit, the forming of a toner image is carried out.  
         [0054]    The toner image is transferred onto the paper that has been guided into position from the paper feed section  107 . After that, the toner image is heated and pressed with the fixing roller. As a result, the toner image is melted and thereby fixed onto the surface of the paper. The write process onto the paper is thus completed, followed by the processes performed at the tail end section  103  such as jogging, stapling and/or punching of grouped output papers, which are then delivered on a tray.  
         [0055]    [0055]FIG. 2 is a block diagram showing the overview of the control section of the aforementioned copier. The control section of the copier controls, by means of a CPU  202  on the image processing board  201 , and further via CPUs  226  and  229  on boards  214  and  230 , respectively, which are located for each unit, those equipment sets each of which constitutes a unit, in a totalized or across-the-board manner. More specifically, the control section of the copier is made up of an operation panel board  214 , a machine control board  230 , a CCD board  209  and the image processing board  201 . The operation panel board  214  is in charge of a user operation panel located on an upper surface of the copier. The machine control board  230  is in charge of each equipment set within the copier. The CCD board  209  provides a mount for the photoelectric conversion element accompanied by its peripheral parts. The image processing board  201  provides a mount for the CPU  202  accompanied by its peripheral parts. The CPU  202  performs a variety of image processing operations on the image data.  
         [0056]    The processing of the image data in a copying mode in the copier is discussed in the following. The images of the original copies fed from the RADF  105  and positioned on the original glass plate  104  are obtained one after another through scanning by means of the scanner unit  106 . The CCD (charge coupled device)  213  on the CCD board  209  in the scanner unit  106  is driven by a CCD control section  211 . The output signal of the CCD goes through a gain adjustment at an analog circuit  212 , and is sent as 8-bit image data from an A/D conversion section  210  to the image processing section  203  on the image processing board  201 . The image data which have gone through a given image processing at the section  203  are then stored into a memory  205  by means of a memory/HDD control section  204 . The image data stored in the memory  205  is then stored into an HDD array  207 , which has four HDDs.  
         [0057]    These processes are carried out on all the original copies that have been placed into the RADF  105 . Thus, the image data for a plurality of pages of the original copies are stored in the HDD array  207 . When the image scanning is finished, image data for each page are read out by means of the memory/HDD control section  204  for a set number of times and then goes through a given image processing at section  203 , and after that, are sent through a laser control section  206  into a laser write section  208 . Therefore, the scanning operation is necessary only once, whether or not the image formation of each original copy has to be repeated for a plurality of times, i.e., for a set number of copies to be produced.  
         [0058]    Now, methods for storing the image data into HDDs are described. The memory/HDD control section  204  includes a memory control IC  902  (shown in FIG. 13) that interfaces with both the memory  205  and the image processing section  203 . The section  204  also includes an HDD array control IC  301  (shown in FIG. 3) that is in charge of the data transfer between the memory control IC  902  and the HDD array  207 . FIG. 3 is a block diagram showing the internal blocks of the HDD array control IC  301 . The IC  301  includes a CPU/DMA I/F section  302  and HDD I/Fs  303 - 306  (or HDD interfaces A-D, wherein the sub-names “A”, “B”, “C” and “D” here mean equal configurations). The CPU/DMA I/F section  302  receives accesses such as “REGISTER”, “READ”, “WRITE” etc., from the CPU  202  and accesses from a DMA control IC  502  (shown in FIG. 5). The HDD I/Fs  303 - 306  (A-D) receive commands and data from the CPU/DMA I/F section  302 , and perform control and data transfer independently to respective HDDs (A-D).  
         [0059]    [0059]FIG. 4 shows registers that are set via the CPU I/F (CPU interface). The registers have a 4-byte configuration, with address 6000H storing HDCON and with address 6008 storing SECCOUNTW. The HDCON performs setting of the HDD array control IC, for instance, switching of HDDs. The SECCOUNTW performs “WRITE” into SECTOR COUNT registers of the HDDs.  
         [0060]    SECCOUNTR_A-D to be stored at the address 6010H as shown in FIG. 4 can read out values read from respective SECTOR COUNT registers of the HDDs (A-D). The SECTOR COUNT registers of the HDDs (A-D) indicate the sector count numbers transferred when the data transfer is performed. In this embodiment, since different settings are not made among the HDDs (A-D), i.e., since settings are equal to each other among the HDDs (A-D), each register for writing into the HDDs (A-D) is configured to allow writing of one value. On the other hand, in this embodiment, since different values can be read out from the HDDs (A-D) simultaneously, each register for readout is configured to allow four values to be read out simultaneously.  
         [0061]    In the same way, respective one of the data “sector number write” (“SECtor NUMber Write”; or SECNUMW in FIG. 4), “sector number read” (“SECtor NUMber Read”; or SECNUMR_ in FIG. 4), “cylinder number LOW write” (“CYLinder number LOw Write”; or CYLLOW in FIG. 4), “cylinder number LOW read” (“CYLinder number LOw Read”; or CYLLOR 13   in FIG. 4), “cylinder number HIGH write” (“CYLinder number HIgh Write”; or CYLHIW in FIG. 4), “cylinder number HIGH read” (“CYLinder number HIgh Read”; or CYLHIR_ in FIG. 4), is stored at respective one of the addresses 6018H, 6020H, 6028H, 6030H, 6038H and 6040H. These addresses are such storage areas. The registers at the addresses 6018-6040H for the HDDs (A-D) indicate values regarding the internal address setting of the HDDs (A-D). The register at 6048H is to issue a command such as a data transfer to the HDDs. Since a command (COMMAND) is only for writing into the HDDs (A-D), there is no register for readout of command (from the HDDs). The status register at 6050H is to read (READ) the statuses (STATUS_A-D) of the HDDs (A-D), which are only read out from the HDDs (A-D), therefore, there is no register for writing them (into the HDDs).  
         [0062]    Next, operations of accessing the HDDs (A-D) by accessing these registers are described. When the settings of the registers are done, then the CPU/DMA I/F section  302  decodes the addresses of the registers and issues IDE I/F signals, i.e., CS (Chip Select) and AD (Address), a R/W setting signal, a register setting value (CPUdata) and a data transfer starting trigger signal RTRG, to the HDD I/Fs  303 - 306  (A-D).  
         [0063]    [0063]FIG. 5 is a block diagram showing inner blocks of one of the HDD I/Fs A-D ( 303 - 306 ). Shown in it is a state machine  501 , which is activated by receiving the data transfer starting trigger signal RTRG and then performs the data transfer into the HDDs (A-D). FIG. 6 shows an example of a timing chart showing signals that occur when the state machines  501  are writing into the HDDs (A-D). In this example, by writing “07” into a register at 6008H, “CS[1:0]=01b, AD[2:0]=011b” is assigned to the HDDs (A-D) and by asserting a DIOW signal, writing that is directed to 07H is performed into the sector count registers of the HDDs (A-D).  
         [0064]    Signals from the CPU/DMA I/F section  302  are simultaneously issued to the HDD I/Fs A-D ( 303 - 306 ). Consequently, IDE signals that are identical to each other are simultaneously issued to the HDDs (A-D). When the writing into the HDDs (A-D) is finished, the state machines  501  issue RSTB (return strobe) signals to the CPU/DMA T/F section  302 . All the HDD I/Fs A-D ( 303 - 306 ) having issued RSTB signals, then the CPU/DMA I/F section  302  allows CPU  202  to proceed to next register setting.  
         [0065]    [0065]FIG. 7 shows an example of signals that occur when the state machines  501  are reading the HDDs (A-D). In this example, by reading a status register that is located at 6050H, “CS[1:0]=01b, AD[2:0]=111b” is assigned from the state machine  501  to the HDD (A-D) and by asserting a DIOR signal, reading out from the status register is performed.  
         [0066]    Signals from the CPU/DMA I/F section  302  are simultaneously issued to the HDD I/Fs A-D ( 303 - 306 ). Consequently, IDE signals that are identical to each other are simultaneously issued to the HDDs (A-D). When the reading of the HDDs (A-D) is finished, the state machines  501  issue RSTB (return strobe) signals to the CPU/DMA I/F section  302 . All the HDD I/Fs A-D ( 303 - 306 ) having issued RSTB signals, then the CPU/DMA I/F section  302  notifies the CPU  202  that the read-out data are valid.  
         [0067]    Next, the DMA transfer from the memory  205  to the HDDs (A-D) is described. FIG. 8 shows an example of the DMA transfer scheme of the HDD I/Fs A-D ( 303 - 306 ). The CPU  202  perform a writing into a register of the HDD array control IC  901  (shown in FIG. 9), which causes the HDD array control IC  901  to perform setting of parameters (such as a transfer sector count number and an address in a storage area needed for the DMA transfer) in HDDs (A-D). After setting the necessary parameters, the CPU  202  writes a command CAH (for DMA writing) into a register for command issuance (COMMAND at 6048H in FIG. 4), which causes the HDD array control IC  901  to issue the command CAH to the HDDs (A-D). The command having been issued, the HDDs (A-D) are brought into a wait state for the data transfer.  
         [0068]    The CPU  202  sets the RW bit of a register for the data transfer of the register (HDCON at 6000H) of the DMA control IC  901  to “1”, thereby activating the data transfer from the memory  205  to the HDDs (A-D). After that, a bit DEXE, which is a MSB data transfer start bit of the register (HDCON at 6000H) of the HDD array control IC  901 , is set, thereby causing the HDD array control IC  901  to receive the data read out by the DMA control IC  502  from the memory  205  and to write it into the HDDs (A-D).  
         [0069]    When the transfer start bit is set, the CPU/DMA I/F section  302  issues the DMA transfer start trigger signal DTRG to each of the state machines  501  (shown in FIG. 5) in the HDD I/Fs A-D ( 303 - 306 ). Then the state machine  501  generates a HDD interface signal at a timing for DMA transfer. When the DMA transfer is finished in accordance with the sector counter number of the setting, the HDDs (A-D) issue interrupts to notify of the completion of the data transfer. More specifically, since each of the HDDs (A-D) are operating with respective independent interfaces, the data transfer rates of the HDDs are different from each other, therefore, each interrupt signal from each of the HDDs (A-D) is connected to the CPU/DMA I/F section  302 , so that when all these interrupt signals have arrived, then an interrupt signal is issued to the CPU  202 . Upon receiving this interrupt, the CPU  202  reads the status register at the address 6050H to check up on the after-DMA-transfer statuses of the HDDs (A-D).  
         [0070]    Now, data transfer modes (for transferring data to the HDDs (A-D)) established in accordance with the present invention are described. There are two types of modes (a first-type mode and a second-type mode) in which the HDD array control IC  901  can make the HDDs (A-D) store the data from the memory control IC  902 . In the first-type mode, the assignment of 64-bit data from the DMA control IC  502  is shown in FIG. 9 and the data bus between the memory control IC  902  and the HDD array control IC  901  is 64-bit, wherein the data are transferred in the order of d 0 , d 1 , d 2 , . . . as shown in FIG. 9.  
         [0071]    Through the HDD I/Fs (A-D), the data are divided into 16-bit sets and are stored into the HDDs (A-D). In order to balance the differences in data transfer rates among the HDDs (A-D), each of the HDD I/Fs (A-D) has FIFOs in a “toggle” manner. Three phases of such a data transfer process using the FIFOs are shown in FIGS.  10 - 12 . When the FIFOs are open for the additional data as in FIGS. 10 and 11, each of the HDD I/Fs (A-D) asserts a REQ signal so as to permit the data transfer. Since the CPU/DMA I/F section  302  is to transfer the data simultaneously to all the HDD I/Fs (A-D) here, such data transfer is performed only when all the HDD I/Fs (A-D) assert the REQ signals.  
         [0072]    As shown in FIGS. 11 and 12, the HDD I/Fs (A-D) start the data transfer to the HDDs (A-D) when one of the FIFOs come into a “full” state due to writing of the data from the CPU/DMA I/F section  302 . Since there are FIFOs in a “toggle” manner as shown in FIG. 11, the data transfer from the CPU/DMA I/F section  302  to the HDD I/Fs and the data transfer from the HDD I/Fs to the HDDs (A-D) can be performed at the same time. As shown in FIG. 12, however, when one of the pair of FIFOs is “full” and the other is engaged in the data transfer to the HDD, the data transfer to the FIFOs are not possible, in which case the corresponding HDD I/F negates REQ signal. When this situation occurs, the data transfer from the CPU/DMA I/F section  302  is not performed, however, the data transfer from the HDD I/Fs to the HDDs can be continued. Thus, this divided storing of data into the four HDDs (A-D) in parallel in this manner attains a remarkable data transfer performance; the overall data transfer speed is about four times as high as the speed that is obtained when using a single HDD.  
         [0073]    Another or the second-type mode for storing data into HDDs is shown in FIG. 13, together with the data format or data layout. In contrast to the first-type mode shown in FIG. 9 in which each of the HDDs (A D) receives respective one of the four 16-bit data sets obtained by dividing the 64-bit data into four buses, this second-type mode does not divide but converts the 64-bit data into 16-bit-wide data parts within the HDD array control IC  901  and then transfers the same 16-bit data part to all the HDDs (A-D). This conversion (no division) of 64-bit data to 16-bit data being performed at the CPU/DMA I/F section  302  (shown in FIG. 3), the operations of each pair of the FIFOs that receive the data and transfer it to the HDDs (A-D) are similar to those explained as above referencing FIGS.  10 - 12 , but, the operation of the second-type mode, as far as its data transfer speed performance is concerned, is merely equivalent to a case when the data from the memory control section  902  are simply transferred into a single HDD, i.e., its speed is equal to the one obtained by a single HDD.  
         [0074]    An advantage in this second-type mode is apparent when one of its HDDs does not work properly. Because the data that is identical to the correct data that might have been lost in the malfunctioning HDD has been stored in other HDDs, the correct data can be read out from such other HDDs that have been working normally. In conclusion, the first-type mode shown in FIG. 9 can improve speed, and the second-type mode shown in FIG. 13 can improve reliability.  
         [0075]    Next, a method for saving the image data by selecting one of these modes is now described. FIG. 14 shows a user operation panel  1401 , which is located at the copier. A LCD  1402  is located in the upper part of the operation panel  1401 . A transparent touch panel (or a touch screen) is located on the surface of the LCD  1402 . The touch panel detects the operation of the keys indicated in the LCD  1402 . Lower than LCD  1402 , and in the bottom center section of the panel  1401 , a numeric keypad  1418  is located, which is useful for inputting numeric values, such as the number of copies to make, etc. To the right of the LCD  1402  and from top to bottom shown are push buttons: an interrupt button  1413 , a reset button  1414 , a stop button  1415  and a start button  1416 . The interrupt button  1413  is located to perform an interrupt-copy function that is used during a copying operation and allows the copier machine to go into another copying operation that is related to a different copying-mode. The reset button  1414  is located to reset settings such as those made by the numeric keypad. The stop button  1415  is to stop the copying operation while the copier is in motion. The start button  1416  starts the copying operation. To the left of the start button  1416  is a document registration button  1417  which is pushed down for a document registration process.  
         [0076]    To operate the copier with its electronic sorting function, first the original copies are placed at the RADF  105 . Then a “SORT” key shown in the LCD  1402  is selected and such state is kept until the start, button  1416  is pushed down and the copying operation with the electronic sorting function is performed. When the image data are stored into the HDDs at each copying operation that uses the electronic sorting function, speed is the priority. Once the copying operation is completed, such image data are not reused. Therefore, a speed-oriented transfer mode that divides and transfers the data shown in FIG. 9 from the CPU  202  into the HDDs (A-D) is selected or set to the HDD array control IC  901 .  
         [0077]    As for the document registration function, which can register a document such as a form image, its registration operation flow is now described with reference to FIG. 15. In order to register a document into the HDDs (A-D), first, the document registration button  1417  in the operation panel  1401  in FIG. 14 is pushed down (step  1501 ). When the button  1417  is pushed down, the LCD  1402  changes from the copy-mode screen into a registered-documents/document-registration-setting screen  1600  shown in FIG. 16. Then settings of a registration number setting key  1601  and a registration name setting key  1602  are performed (step  1502 ). By pushing a registration execution key  1603  (step  1503 ), settings for the registration are finished, thereby returning into the copy-mode screen again ( 1504 ). By pushing down the start button  1416  (step  1505 ) when the settings for registration are thus finished, the original copies are scanned and the data of the document is stored into the HDDs A-D (step  1506 ). When a number of pages according to the setting have been successfully scanned, the document registration is finished (step  1507 ).  
         [0078]    In the document registration, the transfer mode shown in FIG. 13 is set to the HDD array control IC  901 , wherein the same data are transferred to all the HDDs (A-D) and therefore the data are not lost even if a HDD does not work properly. In this manner, by changing the data format (or data layout) used to store the data into the HDD array  207  in response to the intended use of the data, either the speed-oriented data format (or data layout) or the data-reliability-oriented one can be selected. Further, although the data to be stored in the HDDs (A-D) has been shown as image data in the above example, the data may be other data such as management data or control parameters in order to store the initial condition of the system. When the system management data are stored into the HDDs (A-D), it requires reliability rather than speed, therefore the data transfer mode (shown in FIG. 13) that transfers the same data to all the HDDs (A-D) is selected.  
         [0079]    Next, a method for reading out and utilizing the data commonly stored in every one of the four HDDs, such as the above described data of the registered documents, is now described. In this system, correct images of the registered documents can be obtained (or recovered) even when the data are damaged (or mixed up, corrupted, etc.) in one of the HDDs. An example of such an operation is described below. The control flow of the reading out process when the registered documents are read out is explained with reference to FIG. 17.  
         [0080]    When the document registration button  1417  in FIG. 14 is pushed down, the LCD  1402  comes into the document-registration-setting screen  1600  shown in FIG. 16 (step  1701 ). Next, the setting of the registration number  1601  is performed (step  1702 ) and a print document selection key  1604  is pushed so as to select the registered document ( 1703 ). When the selection has been done, the document-registration-setting screen  1600  is turned into the copying-mode screen (step  1704 ). After that, when the start button  1416  is pushed down, the copier machine reads out the image data of the document that has been registered in the HDDs (A-D) and prints out the image ( 1706 ).  
         [0081]    [0081]FIG. 18 is a block diagram of some circuits in the CPU/DMA I/F  302 , which is used when the data are read out from the HDDs (A-D). The data comparison section  1801  receives data input from the FIFOs. The section  1801  performs the data comparison per every “1 word” (or specific bit length data) on the data corresponding to each of the HDDs (A-D) only when the aforementioned registered image is read out. If all the data are equal according to the performed comparison, the data from the HDD (A) are directly input into a data conversion section  1802 . The data conversion section organizes the input 16-bit data into the 64-bit data output, which is sent to the DMA control section  502 . On the other hand, if the data from HDD (A) are compared with the corresponding data from other HDDs (B-D) and they are not equal according to the comparison, for example, if the data from HDD (A) are 0000H and the data from any of the other HDDs (B-D) are FFFFH, then the input to the data conversion section  1802  is switched so that the data from HDD (B) are input to the section  1802 . In this manner, leveraging what is done by the aforementioned process that stores the same data in each HDD, data correction can be made even when a problem occurs in the data in a HDD.  
         [0082]    Further, since the HDD having the data trouble can be detected, such a HDD malfunction can be informed of by displaying a malfunction notice window (shown in FIG. 19) in the LCD  1402  of the user operation panel  1401 . On the other hand, when the image data are being read out from the HDDs (A-D) during a copying operation using the electronic sorting function, the data comparison section  1801  does not provide any substantive effect but just interfaces the data from the HDDs (A-D) with the data conversion section  1802 , and the data conversion section  1802  does not perform data conversion but just interfaces the data with the DMA control section  502 .  
         [0083]    By the way, suppose a document registration is done in the system in the above example of the present invention and after that a HDD is replaced due to its malfunction, etc., and the replacement HDD A 1  that has just been connected to the system instead of the previous HDD A 0  does not have the document registration data as all the other HDDs B-D do. Therefore, in this embodiment of the present invention, after a replacement of a HDD, the document registration data from the other HDDs B-D are copied into the corresponding addresses of the replacement HDD A 1  that has just been connected to the system instead of a previous HDD. To be more precise, when the system power is switched on, processes like setting of data transfer mode, etc., are carried out. Then, the CPU  202  reads the addresses of the HDD management area. In order to determine whether the HDD is a new one or not, the new HDD identification word located in the HDD management area is checked. If a value that shows that the HDD is not a new one has not been written in the “word”, the HDD is recognized as a new or replacement HDD. In this case, this new HDD further receives transfer of the image data of the registered documents from a HDD having a “word” (or “new HDD identification word”) in which a value that shows that the HDD is not a new one is written.  
         [0084]    With reference to the flow chart shown in FIG. 20, the above process flow is described in more detail. After the power switch SW is turned ON (step  2001 ), the CPU  202  performs initial settings (step  2002 ) for the HDDs (A-D) such as data transfer mode, etc. Next, the “new HDD identification word” checks are performed against the HDDs (A-D) (step  2003 ), to detect whether or not each of them is a replacement HDD. If all the HDDs are new or replacement HDDs (step  2004 ), “word” data that assumes that the HDD is not a new one is written into each “new HDD identification word” (step  2010 ) and the process is ended (i.e., HDDs detected as new HDDs in step  2003  no more have to be treated as new HDDs). If none of the HDDs is a new or replacement HDD (step  2005 ), nothing is done and the process is ended. If there is a new or replacement HDD, a management area of a non-new HDD is read to check whether there is a registered image document ( 2006 ), wherein if the check result is NO (there is no registered image document in this non-new HDD), “word” data that assumes that the HDD is not a new one is written into a “new HDD identification word” for each of the new HDDs (step  2010 ) and the process is ended (i.e., HDDs detected as new HDDs in step  2003  no more have to be treated as new HDDs). If the check result is YES (there are registered image documents in the non-new HDD), the registered image documents in the non-new HDD are read out in the order of management number and extracted (or developed) into the image memory  205  (step  2007 ), then the image is transferred to the new HDD (step  2008 ). In this manner, all the registered images are transferred and its completion is checked (step  2009 ). When the transfer of all the registered images is completed, then “word” data that assumes that the HDD is not a new one is written into a “new HDD identification word” for each of the new HDDs (step  2010 ) and the process is ended (i.e., HDDs detected as new HDDs in step  2003  no more have to be treated as new HDDs). If such writing of the data of the registered documents into a new or replacement HDD is accomplished, written data that is now present in this HDD can be used, especially when it further happens that another HDD has some trouble. Therefore, this feature can further reduce the chances of loss with regard to the data of the registered documents.  
         [0085]    The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.  
         [0086]    This application claims priority rights of and is based on Japanese patent application No. JPAP2001-287545 filed on Sep. 20, 2001 in the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.