Patent Publication Number: US-2018052749-A1

Title: Information processing system and information processing method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2016-160288, filed on Aug. 18, 2016, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein are related to an information processing system and an information processing method. 
     BACKGROUND 
     A storage device that performs mirroring control copies data from one disk (copy source disk) to another disk (copy destination disk). If an error occurs on the copy source disk during a copy process, the copy process is generally aborted. In this case, since the copy process is not completed and the contents in the copy destination disk are not guaranteed, the copy destination disk is separated from the mirroring, and as a result, the copy source disk becomes an operation disk. However, since the error occurs during the copy process in the copy source disk, the copy source disk does not have a sufficient qualification as an operation disk. 
     Therefore, there has been a storage device in which, when an error occurs in the copy source disk during the copy process, the copy source disk is separated from the mirroring and the copy destination disk is used as an operation disk. 
     Related techniques are disclosed in, for example, Japanese Laid-Open Patent Publication No. 2010-186285. 
     SUMMARY 
     According to an aspect of the present invention, provided is an information processing device including a memory and a processor coupled to the memory. The processor is configured to perform data copy of copying data from a first storage device to a second storage device. The processor is configured to receive a first write request while performing the data copy. The first write request requests to write first data in a first area of the first storage device. The processor is configured to perform first data write of writing the first data in the first area. The processor is configured to perform second data write of writing the first data in a second area of the second storage device. The second area corresponds to the first area. The processor is configured to store abnormality information in the memory upon detecting normal completion of the second data write and an error occurred in the first data write. The abnormality information indicates the first area. The processor is configured to continuously perform the data copy while excluding data stored in the first area from copy-target data on basis of the abnormality information stored in the memory. The copy-target data is data to be copied by the data copy. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 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 
         FIG. 1  is a diagram illustrating an example of an information processing system according to a first embodiment; 
         FIG. 2  is a diagram illustrating an example of a storage device according to a second embodiment; 
         FIG. 3  is a diagram illustrating an exemplary hardware configuration of a CM according to the second embodiment; 
         FIG. 4  is a diagram illustrating an exemplary functional configuration of the CM according to the second embodiment; 
         FIG. 5A  is a diagram illustrating a format of a mirror disk management table according to the second embodiment; 
         FIG. 5B  is a diagram illustrating a specific example of the mirror disk management table according to the second embodiment; 
         FIGS. 6A and 6B  are diagrams illustrating examples of a disk state according to the second embodiment; 
         FIG. 7  is a diagram illustrating examples of a write area management table and the like according to the second embodiment; 
         FIG. 8  is a flowchart illustrating an example of a normal write process according to the second embodiment; 
         FIG. 9  is a flowchart illustrating an example of a normal read process according to the second embodiment; 
         FIG. 10  is a flowchart illustrating an example of a copy process according to the second embodiment; 
         FIG. 11  is a flowchart illustrating an example of the copy process according to the second embodiment; 
         FIG. 12  is a flowchart illustrating an example of a write-in-copy process according to the second embodiment; 
         FIG. 13  is a flowchart illustrating an example of a read-in-copy process according to the second embodiment; 
         FIG. 14  is a flowchart illustrating an example of the read-in-copy process according to the second embodiment; and 
         FIGS. 15A to 15C  are diagrams illustrating examples of a write-in-copy process according to the second embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the storage device in which the copy source disk is separated from the mirroring and the copy destination disk is used as an operation disk, when the error occurs in the copy source disk during the copy process, the copy source disk does not have the qualification as an operation disk and the data may be non-guaranteed even in the copy destination disk. 
     Hereinafter, embodiments will be described with reference to the accompanying drawings. 
     First Embodiment 
       FIG. 1  is a diagram illustrating an example of an information processing system according to a first embodiment. The information processing system  1  includes an information processing device  2 , a first storage device  5 , and a second storage device  6 . For example, the first storage device  5  and the second storage device  6  are hard disk drives (HDDs). 
     The information processing device  2  includes a storage unit  3  and a control unit  4 . For example, the storage unit  3  is a random access memory (RAM) and the like. For example, a processor performs a required process to implement the control unit  4 . 
     The control unit  4  performs data copy of copying data from the first storage device  5  to the second storage device  6 . The second storage device  6  is a storage device which becomes a duplication of the first storage device  5 . That is, the first storage device  5  is a storage device of a copy source. The second storage device  6  is a storage device of a copy destination. The control unit  4 , for example, copies data stored in an area  5   a  of the first storage device  5  to an area  6   a  of the second storage device  6 . 
     The control unit  4  may receive a write request while performing the data copy. For example, the control unit  4  receives the write request from a higher-level device. The higher-level device is, for example, a host device. When the control unit  4  receives the write request, the control unit  4  writes data (hereinafter, referred to as “write data”) to be written, which corresponds to the write request, in an area  5   b  of the first storage device  5  and an area  6   b  of the second storage device  6 . 
     When the control unit  4  detects normal writing of the write data by the second storage device  6  and abnormal writing of the write data by the first storage device  5  as a result of the write request while performing the data copy, the control unit  4  stores abnormality information  3   a  in the storage unit  3 . The abnormality information  3   a  is information for identifying a write-abnormality area in the first storage device  5 . For example, the abnormality information  3   a  indicates a write-abnormality area X. The write-abnormality area X is information for identifying the area  5   b.    
     The control unit  4  continuously performs the data copy while excluding the data corresponding to the write-abnormality area from data (hereinafter, referred to as “copy-target data”) to be copied in the data copy on the basis of the abnormality information  3   a . For example, the control unit  4  continuously performs the data copy while excluding the data corresponding to the area  5   b  from the copy-target data in the data copy. 
     As described above, the information processing device  2  prevents indefinite data from being copied to the second storage device  6  from the first storage device  5  by excluding the data corresponding to the write-abnormality area from the copy-target data in the data copy. As a result, the information processing device  2  prevents a state in which the second storage device  6  which is the storage device of the copy destination does not guarantee data. Since the information processing device  2  normally writes the write data of the write request instead of the data excluded from the copy-target data, the second storage device  6  which is the storage device of the copy destination may be used as a storage device that may guarantee data. 
     When the first storage device  5  and the second storage device  6  constitute mirroring, the information processing device  2  may exclude the first storage device  5  from the mirroring constituents after completing the data copy of copying data from the first storage device  5  to the second storage device  6 . 
     Accordingly, the information processing system  1  or the information processing device  2  may guarantee data in the storage device of the copy destination even when an error occurs in the storage device of the copy source during a copy process. 
     Second Embodiment 
       FIG. 2  is a diagram illustrating an example of a storage device according to a second embodiment. A storage device  100  stores therein data handled by a host device  400 . The storage device  100  includes a controller module (CM)  200  and a device enclosure (DE)  300 . The CM  200  controls an access to the DE  300  from the host device  400 . 
     The DE  300  is a disk array device capable of housing a plurality of storage devices. The DE  300  includes HDDs  310 ,  320 , and  330 . The DE  300  may include more than three HDDs. The DE  300  may house solid state drives (SSDs) as the storage devices. 
     The storage device  100  and the host device  400  are coupled to each other through a network. For example, the storage device  100  and the host device  400  are coupled to each other by a transmission scheme such as a Fibre Channel (FC) or the like. 
     The CM  200  may manage the HDDs  310  and  320  as a redundant array of inexpensive disks (RAID). The CM  200  designates a logical block address (LBA) of a logical volume set in storage areas of the HDDs  310  and  320  to accesses the HDDs  310  and  320 . The CM  200  controls the HDDs  310  and  320  as RAID1. That is, the CM  200  performs mirroring control on the HDDs  310  and  320 . The HDDs  310  and  320  serve as mirror disks. The CM  200  stores information used for each process in the HDD  330 . Therefore, the HDD  330  serves as a management disk. 
     It is assumed that the HDD  320  is a newly introduced HDD as a replacement. Therefore, even though the HDD  320  is an HDD among the mirroring constituents, the HDD  320  does not yet store therein data which is duplicated with data stored in the HDD  310 . The CM  200  detects addition of the HDD  320  due to a change in the configuration of the storage devices as the mirroring constituents. In the second embodiment, each process is performed while the data stored in the HDDs  310  and  320  do not coincide with each other. 
     The storage device  100  is an example of the information processing system  1  according to the first embodiment. The CM  200  is an example of the information processing device  2  according to the first embodiment. 
       FIG. 3  is a diagram illustrating an exemplary hardware configuration of the CM according to the second embodiment. The CM  200  includes a central processing unit (CPU)  201 , a RAM  202 , a flash memory  203 , an input-output controller (IOC)  204 , a disk adapter (DA)  205 , and a channel adapter (CA)  206 . 
     The CPU  201  controls information processing of the CM  200 . The CPU  201  may be replaced by a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like. The CPU  201  may be a multi-processor. 
     The RAM  202  is a main storage device of the CM  200 . The RAM  202  temporarily stores therein at least a part of a program of an operating system (OS) or an application program executed by the CPU  201 . The RAM  202  also stores therein various data used for the information processing performed by the CPU  201 . 
     The flash memory  203  is an auxiliary storage device of the CM  200 . The flash memory  203  is a non-volatile storage device. The flash memory  203  stores therein the program of the OS, the application program, and various data. The CM  200  may include, as the auxiliary storage device, an HDD instead of the flash memory  203 . 
     The IOC  204  controls the access to the DE  300  from the host device  400 . The DA  205  is an interface for communication with the DE  300 . The CA  206  is an interface for communication with the host device  400 . 
       FIG. 4  is a diagram illustrating an exemplary functional configuration of the CM according to the second embodiment. The CM  200  includes a storage unit  210  and a control unit  220 . 
     The storage unit  210  stores therein a mirror disk management table  211 , a write area management table  212 , an error area management table  213 , and a copy management table  214 . 
     The mirror disk management table  211  indicates information on the HDDs as the mirroring constituents. The write area management table  212  indicates areas (hereinafter, referred to as write completion areas) where data has been written. The error area management table  213  indicates areas where an error has occurred. The copy management table  214  indicates areas where data has been copied. The HDD  330  stores therein the mirror disk management table  211  and the write area management table  212  while the storage device  100  is in a power-off state. 
     The control unit  220  includes a mirror unit  221 , a copy unit  222 , and a configuration management unit  223 . The mirror unit  221  performs mirroring control on the HDDs  310  and  320 . In a case where the mirror unit  221  receives a write request from the host device  400  while the copy process to be described below is not performed, the mirror unit  221  performs a normal write process. The normal write process will be described later in detail. In a case where the mirror unit  221  receives a write request from the host device  400  during the copy process, the mirror unit  221  performs a write-in-copy process. The write-in-copy process will be described later in detail. 
     In a case where the mirror unit  221  receives a read request from the host device  400  while the copy process is not performed, the mirror unit  221  performs a normal read process. The normal read process will be described later in detail. In a case where the mirror unit  221  receives a read request from the host device  400  during the copy process, the mirror unit  221  performs a read-in-copy process. The read-in-copy process will be described later in detail. 
     The copy unit  222  performs the copy process. When the copy unit  222  performs the copy process, the copy unit  222  copies data stored in a copy source disk to a copy destination disk. The copy source disk and the copy destination disk are set by the configuration management unit  223 . 
     The configuration management unit  223  performs an update process of updating the mirror disk management table. The configuration management unit  223  sets any one of the HDDs  310  and  320  as the copy source disk. The configuration management unit  223  may determine which one of HDDs  310  and  320  is to be set as the copy source disk in accordance with an instruction from the host device  400 . The configuration management unit  223  sets an HDD other than the copy source disk as the copy destination disk. The setting of the copy source disk and the copy destination disk will be described later in detail. 
     After the storage device  100  is powered on, the configuration management unit  223  reads the mirror disk management table  211  and the write area management table  212  from the HDD  330 . The configuration management unit  223  stores the read mirror disk management table  211  and the write area management table  212  in the storage unit  210 . 
       FIGS. 5A and 5B  are diagrams illustrating an example of a mirror disk management table according to the second embodiment.  FIG. 5A  illustrates a format of the mirror disk management table  211 . The mirror disk management table  211  includes items of a write area management table use flag, a write area management table disk number, and a write area management table offset. Further, the mirror disk management table  211  includes items of the number of mirror disks, physical disk number-1, disk state-1, physical disk number-2, disk state-2, . . . , physical disk number-n, and disk state-n. 
     The item of the write area management table use flag indicates whether the write area management table  212  is used. The item of the write area management table use flag indicates any one of “valid” and “invalid”. The “valid” indicates that the write area management table  212  is used. The “invalid” indicates that the write area management table  212  is not used. When the write area management table use flag is “valid”, the copy unit  222  performs data copy for the write completion areas. When the write area management table use flag is “invalid”, the copy unit  222  performs data copy for the entire copy source disk. In the second embodiment, it is assumed that “valid” is set in the item of the write area management table use flag. 
     The item of the write area management table disk number indicates a device number of a management disk storing the write area management table  212 . The item of the write area management table offset indicates a location where the write area management table  212  is stored in the management disk. 
     The item of the number of mirror disks indicates the number of mirror disks which exist in the DE  300 . The item of the physical disk number indicates the device number of a mirror disk. The item of the disk state indicates a state of the mirror disk. The item of the disk state indicates any one of “ACTIVE”, “COPY”, and “INVALID”. The “ACTIVE” indicates that the mirror disk is an operation disk. Further, the “ACTIVE” indicates that the mirror disk is the copy source disk during the copy process. The “COPY” indicates that the mirror disk is the copy destination disk during the copy process. The “INVALID” indicates that the mirror disk is separated from the mirroring configuration. That is, the “INVALID” indicates that the mirror disk is excluded from the mirroring constituents. Further, the “INVALID” indicates that the mirror disk is not an operation disk. 
       FIG. 5B  illustrates a specific example of a mirror disk management table  211   a . The mirror disk management table  211   a  indicates that the write area management table  212  is used (“valid”). The mirror disk management table  211   a  indicates that the device number of the management disk is “0x00010000”. The mirror disk management table  211   a  indicates that the write area management table  212  is stored at a location of “0x00002000” in the management disk. The mirror disk management table  211   a  indicates that the number of mirror disks which exist in the DE  300  is “2”. The mirror disk management table  211   a  indicates that the device number of the copy source disk (“ACTIVE”) is “0x00010001”. The mirror disk management table  211   a  indicates that the device number of the copy destination disk (“COPY”) is “0x00010002”. 
       FIGS. 6A and 6B  are diagrams illustrating examples of a disk state according to the second embodiment.  FIG. 6A  illustrates a state before the copy process.  FIG. 6A  illustrates that the item of the disk state in the mirror disk management table  211  corresponding to the HDDs  310  and  320  is “ACTIVE”. 
     Before the copy unit  222  performs the copy process, the configuration management unit  223  sets one HDD, among the HDDs having “ACTIVE” in the item of the disk state in the mirror disk management table  211 , as the copy source disk. The configuration management unit  223  sets another HDD, among the HDDs having “ACTIVE” in the item of the disk state in the mirror disk management table  211 , as the copy destination disk. The configuration management unit  223  registers “COPY” in the item of the disk state in the mirror disk management table  211  corresponding to the HDD set as the copy destination disk.  FIG. 6B  illustrates that the HDD  310  is set as the copy source disk (the disk state is “ACTIVE”) and the HDD  320  is set as the copy destination disk (the disk state is “COPY”). The HDD  320  is an operation disk even when the HDD  320  is set as the copy destination disk. 
       FIG. 7  is a diagram illustrating examples of a write area management table and the like, according to the second embodiment.  FIG. 7  illustrates that the write area management table  212 , the error area management table  213 , and the copy management table  214  have a relationship with a logical volume  310   a  of the HDD  310  and a logical volume  320   a  of the HDD  320 . 
     The write area management table  212  indicates, with bits, whether data has been written in an area of the logical volumes  310   a  and  320   a  divided into units of 2 MB corresponding to the respective bits. The write area management table  212  may indicate, with bits, whether data has been written in an area of the physical volumes of the HDDs  310  and  320  divided into units of 2 MB corresponding to the respective bits. Each bit of the write area management table  212  indicates any one of “0” and “1”. When the bit is “0”, it indicates that no data has been written in an area corresponding to the bit. When the bit is “1”, it indicates that data has been written in the area corresponding to the bit. When data is written in an area of the logical volume  310   a  and an area of the logical volume  320   a  corresponding to the area of the logical volume  310   a , the mirror unit  221  sets the bit corresponding to the areas of the logical volumes  310   a  and  320   a  as “1”. When data is written in one of an area of the logical volume  310   a  and an area of the logical volume  320   a  corresponding to the area the logical volume  310   a , the mirror unit  221  sets the bit corresponding to the area where the data is written as “1”. 
     The error area management table  213  indicates, with bits, whether an error has occurred in an area of the logical volumes  310   a  and  320   a  divided into units of 2 MB corresponding to the respective bits. The error area management table  213  may indicate, with bits, whether an error has occurred in an area of physical volumes of the HDDs  310  and  320  divided into units of 2 MB corresponding to the respective bits. Each bit of the error area management table  213  indicates any one of “0” and “1”. When the bit is “0”, it indicates that no error has occurred in an area corresponding to the bit. When the bit is “1”, it indicates that an error has occurred in the area corresponding to the bit. For example, when an error occurs in an area of the logical volume  310   a , the mirror unit  221  sets a bit corresponding to the area (hereinafter, referred to as an “error area”) where the error occurs as “1”. 
     The copy management table  214  indicates, with bits, whether data dopy is completed between areas of the logical volumes  310   a  and  320   a  divided into units of 2 MB correspond to the respective bits. The copy management table  214  may indicate, with bits, whether data dopy is completed between areas of the physical volumes of the HDDs  310  and  320  divided into units of 2 MB correspond to the respective bits. Each bit of the copy management table  214  indicates any one of “0” and “1”. When the bit is “0”, it indicates that data dopy is not completed between areas corresponding to the bit. When the bit is “1”, it indicates that data dopy is completed between areas corresponding to the bit. For example, when data copy from an area of the logical volume  310   a  is completed, the copy unit  222  sets the bit corresponding to the area from which the data is copied as “1”. 
     Subsequently, each process is described with reference to a flowchart. Since the HDD  320  is a newly introduced HDD as a replacement, even though the HDD  320  is an HDD among the mirroring constituents, the HDD  320  does not yet store therein data which is duplicated with data stored in the HDD  310 . 
     First, a case where a copy process is not performed in the CM  200  is described. A case where the CM  200  receives an access request for the DE  300  from the host device  400  is described with reference to a flowchart. 
       FIG. 8  is a flowchart illustrating an example of a normal write process according to the second embodiment. The copy process is not performed in the control unit  220 , and the control unit  220  performs the normal write process upon receiving a write request from the host device  400 . 
     (S 11 ) The mirror unit  221  writes data in areas in the logical volumes  310   a  and  320   a  designated by the write request. 
     (S 12 ) The mirror unit  221  determines whether an error occurs in the data write. When it is determined that an error occurs, the mirror unit  221  proceeds to S 13 . When no error occurs, the mirror unit  221  proceeds to S 17 . 
     (S 13 ) The mirror unit  221  determines whether the error occurs in both the HDDs  310  and  320 . When it is determined that the error occurs in both the HDDs  310  and  320 , the mirror unit  221  proceeds to S 15 . When it is determined that the error occurs in any one of HDDs  310  and  320 , the mirror unit  221  proceeds to S 14 . 
     (S 14 ) The configuration management unit  223  separates the HDD in which the error occurs from the mirroring configuration. The configuration management unit  223  registers “INVALID” in the item of the disk state in the mirror disk management table  211  corresponding to the HDD in which the error occurs. Thereafter the configuration management unit  223  proceeds to S 17 . 
     (S 15 ) The configuration management unit  223  separates both the HDDs  310  and  320  from the mirroring configuration. The configuration management unit  223  registers “INVALID” in the item of the disk state in the mirror disk management table  211  corresponding to both the HDDs  310  and  320 . 
     (S 16 ) The mirror unit  221  transmits an error notification to the host device  400 . The mirror unit  221  ends the normal write process. 
     (S 17 ) The mirror unit  221  sets the bit corresponding to the area where the data is written as “1” by referring to the write area management table  212 . 
     (S 18 ) The mirror unit  221  transmits a normality notification to the host device  400 . The mirror unit  221  ends the normal write process. 
       FIG. 9  is a flowchart illustrating an example of a normal read process according to the second embodiment. The copy process is not performed in the control unit  220 , and the control unit  220  performs the normal read process upon receiving a read request from the host device  400 . 
     (S 21 ) The mirror unit  221  identifies a bit of the write area management table  212  corresponding to an area designated by the read request. The mirror unit  221  determines whether the area corresponding to the identified bit is a write completion area. When it is determined that the area corresponding to the identified bit is a write completion area (the identified bit is “1”), the mirror unit  221  proceeds to S 22 . When it is determined that the area corresponding to the identified bit is not a write completion area (the identified bit is “0”), the mirror unit  221  proceeds to S 31 . 
     (S 22 ) The mirror unit  221  reads data from the area designated by the read request in the HDD  310  (logical volume  310   a ) or the HDD  320  (logical volume  320   a ). 
     (S 23 ) The mirror unit  221  determines whether an error occurs in the data read. When it is determined that an error occurs, the mirror unit  221  proceeds to S 25 . When it is determined that no error occurs, the mirror unit  221  proceeds to S 24 . 
     (S 24 ) The mirror unit  221  transmits a normality notification to the host device  400 . The mirror unit  221  ends the normal read process. 
     (S 25 ) The mirror unit  221  reads data from the area designated by the read request in the logical volume of an HDD other than the HDD on which the data read is performed in S 22 . For example, when the HDD on which the data read is performed in S 22  is the HDD  310 , the mirror unit  221  reads data from the area designated by the read request in the HDD  320 . 
     (S 26 ) The mirror unit  221  determines whether the error occurs in both the HDDs  310  and  320 . When it is determined that the error occurs in both the HDDs  310  and  320 , the mirror unit  221  proceeds to S 29 . When it is determined that no error occurs in either the HDD  310  or the HDD  320 , the mirror unit  221  proceeds to S 27 . 
     (S 27 ) The configuration management unit  223  separates an HDD in which the error occurs from the mirroring configuration. The configuration management unit  223  registers “INVALID” in the item of the disk state in the mirror disk management table  211  corresponding to the HDD in which the error occurs. 
     (S 28 ) The mirror unit  221  transmits a normality notification to the host device  400 . The mirror unit  221  ends the normal read process. 
     (S 29 ) The configuration management unit  223  separates both the HDDs  310  and  320  from the mirroring configuration. The configuration management unit  223  registers “INVALID” in the item of the disk state in the mirror disk management table  211  corresponding to the HDDs  310  and  320 . 
     (S 30 ) The mirror unit  221  transmits an error notification to the host device  400 . The mirror unit  221  ends the normal read process. 
     (S 31 ) The mirror unit  221  transmits zero data to the host device  400 . Herein, the zero data is data indicating that no data exists and for example, data represented by a row of “0”s as bit values. The mirror unit  221  ends the normal read process. 
     Subsequently, a case where the copy process is performed in the CM  200  is described with reference to a flowchart. Further, a case where the CM  200  receives an access request for the DE  300  from the host device  400  during the copy process is described with reference to a flowchart. 
     In the following description, it is assumed that the HDD  310  is the copy source disk and the HDD  320  is the copy destination disk. Before the copy unit  222  starts the copy process, the configuration management unit  223  registers “COPY” in the item of the disk state in the mirror disk management table  211  corresponding to the copy destination disk (HDD  320 ). The item of the disk state in the mirror disk management table  211  corresponding to the copy source disk (HDD  310 ) is “ACTIVE”. 
       FIG. 10  and  FIG. 11  are flowcharts illustrating an example of the copy process according to the second embodiment. The control unit  220  starts to perform the copy process at a predetermined timing. The predetermined timing may be a preset timing or a timing when the copy unit  222  receives an instruction to start the copy process from the host device  400 . 
     (S 41 ) The copy unit  222  selects one bit of the write area management table  212 . The copy unit  222  determines whether an area corresponding to the selected bit is a write completion area. When it is determined that the area corresponding to the selected bit is a write completion area (the selected bit is “1”), the copy unit  222  proceeds to S 42 . When it is determined that the area corresponding to the selected bit is not a write completion area (the selected bit is “0”), the mirror unit  221  proceeds to S 48 . 
     (S 42 ) The copy unit  222  identifies the bit of the error area management table  213  corresponding to the bit selected in S 41 . The copy unit  222  determines whether an area corresponding to the identified bit is an error area. When it is determined that the area corresponding to the identified bit is an error area (the identified bit is “1”), the copy unit  222  proceeds to S 48 . When it is determined that the area corresponding to the identified bit is not an error area (the identified bit is “0”), the mirror unit  221  proceeds to S 43 . 
     (S 43 ) The copy unit  222  reads data from the area of the logical volume  310   a  of the copy source disk corresponding to the bit selected in S 41 . 
     (S 44 ) The copy unit  222  determines whether an error occurs in the data read performed on the copy source disk. When it is determined that an error occurs, the copy unit  222  proceeds to S 49 . When it is determined that no error occurs, the copy unit  222  proceeds to S 45 . 
     (S 45 ) The copy unit  222  writes the data read in S 43  in an area of the logical volume  320   a  of the copy destination disk corresponding to the bit selected in S 41 . 
     (S 46 ) The copy unit  222  determines whether an error occurs in the data write performed on the copy destination disk. When it is determined that an error occurs, the copy unit  222  proceeds to S 49 . When it is determined that no error occurs, the copy unit  222  proceeds to S 47 . 
     (S 47 ) The copy unit  222  identifies the bit of the copy management table  214  corresponding to the bit selected in S 41 . The copy unit  222  sets the identified bit as “1”. 
     (S 48 ) The copy unit  222  determines whether all bits of the write area management table  212  are selected. When it is determined that all bits are selected, the copy unit  222  proceeds to S 51 . When it is determined that some of the bits are not selected, the copy unit  222  proceeds to S 41 . 
     (S 49 ) The copy unit  222  aborts the data copy. 
     (S 50 ) The configuration management unit  223  separates the copy destination disk from the mirroring configuration. The configuration management unit  223  registers “INVALID” in the item of the disk state in the mirror disk management table  211  corresponding to the copy destination disk. The configuration management unit  223  proceeds to S 53 . 
     (S 51 ) The copy unit  222  determines whether information representing an error area is registered (the bit is “1”) by referring to the error area management table  213 . When it is determined that the information representing an error area is registered, the copy unit  222  proceeds to S 52 . When it is determined that the information representing an error area is not registered, the configuration management unit  223  registers “ACTIVE” in the item of the disk state in the mirror disk management table  211  corresponding to the copy source disk and the copy destination disk. The copy unit  222  ends the copy process. 
     (S 52 ) The configuration management unit  223  separates the copy source disk from the mirroring configuration. The configuration management unit  223  registers “INVALID” in the item of the disk state in the mirror disk management table  211  corresponding to the copy source disk. The configuration management unit  223  registers “ACTIVE” in the item of the disk state in the mirror disk management table  211  corresponding to the copy destination disk. 
     The mirror unit  221  refers to the mirror disk management table  211  to count the number of mirror disks. The mirror unit  221  aborts the control of the mirroring when the number of mirror disks is one (when the number of HDDs having “ACTIVE” in the item of the disk state in the mirror disk management table  211  is one). 
     (S 53 ) The copy unit  222  deletes the information registered in the error area management table  213 . That is, the copy unit  222  initializes the error area management table  213 . The copy unit  222  ends the copy process. 
       FIG. 12  is a flowchart illustrating an example of a write-in-copy process according to the second embodiment. The control unit  220  performs the write-in-copy process upon receiving a write request from the host device  400  during the copy process. 
     (S 61 ) The mirror unit  221  identifies the bit of the error area management table  213  corresponding to an area designated by the write request. The mirror unit  221  determines whether an area corresponding to the identified bit is an error area. When it is determined that the area corresponding to the identified bit is an error area (the identified bit is “1”), the mirror unit  221  proceeds to S 69 . When it is determined that the area corresponding to the identified bit is not an error area (the identified bit is “0”), the mirror unit  221  proceeds to S 62 . 
     (S 62 ) The mirror unit  221  writes data in the area designated by the write request among the areas of the logical volume  310   a  of the copy source disk. The mirror unit  221  writes the data in the area designated by the write request among the areas of the logical volume  320   a  of the copy destination disk. 
     (S 63 ) The mirror unit  221  determines whether an error occurs in the data write. When it is determined that an error occurs, the mirror unit  221  proceeds to S 66 . When it is determined that no error occurs, the mirror unit  221  proceeds to S 64 . 
     (S 64 ) The mirror unit  221  sets the bit corresponding to the area where the data is written as “1”, in the write area management table  212 . 
     (S 65 ) The mirror unit  221  transmits a normality notification to the host device  400 . The mirror unit  221  ends the write-in-copy process. 
     (S 66 ) The mirror unit  221  determines whether the error occurs in the copy source disk. When it is determined that the error occurs in the copy source disk, the mirror unit  221  proceeds to S 70 . When it is determined that the error occurs in the copy destination disk, the mirror unit  221  proceeds to S 67 . 
     (S 67 ) The copy unit  222  aborts the data copy. 
     (S 68 ) The configuration management unit  223  separates the copy destination disk from the mirroring configuration. The configuration management unit  223  registers “INVALID” in the item of the disk state in the mirror disk management table  211  corresponding to the copy destination disk. The configuration management unit  223  proceeds to S 64 . 
     (S 69 ) The mirror unit  221  writes the data in the area designated by the write request among the areas of the logical volume  320   a  of the copy destination disk. 
     (S 70 ) The mirror unit  221  determines whether an error occurs in the copy destination disk. When it is determined that the error occurs in the copy destination disk, the mirror unit  221  proceeds to S 72 . When it is determined that no error occurs in the copy destination disk, the mirror unit  221  proceeds to S 71 . 
     (S 71 ) The mirror unit  221  sets the bit of the error area management table  213  corresponding to the error area as “1”. The mirror unit  221  proceeds to S 64 . 
     (S 72 ) The copy unit  222  aborts the data copy. 
     (S 73 ) The configuration management unit  223  separates the copy destination disk from the mirroring configuration. The configuration management unit  223  registers “INVALID” in the item of the disk state in the mirror disk management table  211  corresponding to the copy destination disk. 
     (S 74 ) The mirror unit  221  deletes the information registered in the error area management table  213 . That is, the mirror unit  221  initializes the error area management table  213 . 
     (S 75 ) The mirror unit  221  transmits an error notification to the host device  400 . The mirror unit  221  ends the write-in-copy process. 
       FIG. 13  and  FIG. 14  are flowcharts illustrating an example of the read-in-copy process according to the second embodiment. The control unit  220  performs the read-in-copy process upon receiving a read request from the host device  400  during the copy process. 
     (S 81 ) The mirror unit  221  identifies the bit of the write area management table  212  corresponding to an area designated by the read request. The mirror unit  221  determines whether an area corresponding to the identified bit is an write completion area. When it is determined that the area corresponding to the identified bit is a write completion area (the identified bit is “1”), the mirror unit  221  proceeds to S 82 . When it is determined that the area corresponding to the identified bit is not a write completion area (the identified bit is “0”), the mirror unit  221  proceeds to S 88 . 
     (S 82 ) The mirror unit  221  identifies the bit of the error area management table  213  corresponding to the area designated by the read request. The mirror unit  221  determines whether an area corresponding to the identified bit is an error area. When it is determined that the area corresponding to the identified bit is an error area (the identified bit is “1”), the mirror unit  221  proceeds to S 89 . When it is determined that the area corresponding to the identified bit is not an error area (the identified bit is “0”), the mirror unit  221  proceeds to S 83 . 
     (S 83 ) The mirror unit  221  reads data from the area designated by the read request among the areas of the logical volume  310   a  of the copy source disk. 
     (S 84 ) The mirror unit  221  determines whether an error occurs in the data read performed on the copy source disk. When it is determined that an error occurs, the mirror unit  221  proceeds to S 85 . When it is determined that no error occurs, the mirror unit  221  proceeds to S 91 . 
     (S 85 ) The mirror unit  221  identifies the bit of the copy management table  214  corresponding to the area designated by the read request. The mirror unit  221  determines whether an area corresponding to the identified bit is the area (hereinafter, referred to as a “copy completion area”) where the copy is completed. When it is determined that the area corresponding to the identified bit is a copy completion area (the identified bit is “1”), the mirror unit  221  proceeds to S 86 . When it is determined that the area corresponding to the identified bit is not a copy completion area (the identified bit is “0”), the mirror unit  221  proceeds to S 94 . 
     (S 86 ) The mirror unit  221  reads data in the area designated by the read request among the areas of the logical volume  320   a  of the copy destination disk. 
     (S 87 ) The mirror unit  221  determines whether an error occurs in the data read performed on the copy destination disk. When an error occurs, the mirror unit  221  proceeds to S 94 . When no error occurs, the mirror unit  221  proceeds to S 92 . 
     (S 88 ) The mirror unit  221  transmits zero data to the host device  400 . The mirror unit  221  ends the read-in-copy process. 
     (S 89 ) The mirror unit  221  reads data in the area designated by the read request among the areas of the logical volume  320   a  of the copy destination disk. 
     (S 90 ) The mirror unit  221  determines whether an error occurs in the data read performed on the copy destination disk. When it is determined that an error occurs, the mirror unit  221  proceeds to S 94 . When it is determined that no error occurs, the mirror unit  221  proceeds to S 98 . 
     (S 91 ) The mirror unit  221  transmits a notification indicating that the data is normally read from the copy source disk to the host device  400 . The mirror unit  221  ends the read-in-copy process. 
     (S 92 ) The mirror unit  221  sets the bit of the error area management table  213  corresponding to the error area as “1”. 
     (S 93 ) The mirror unit  221  transmits a notification indicating that the data is normally read from the copy destination disk to the host device  400 . The mirror unit  221  ends the read-in-copy process. 
     (S 94 ) The copy unit  222  aborts the data copy. 
     (S 95 ) The configuration management unit  223  separates the copy destination disk from the mirroring configuration. The configuration management unit  223  registers “INVALID” in the item of the disk state in the mirror disk management table  211  corresponding to the copy destination disk. 
     (S 96 ) The mirror unit  221  deletes the information registered in the error area management table  213 . That is, the mirror unit  221  initializes the error area management table  213 . 
     (S 97 ) The mirror unit  221  transmits an error notification to the host device  400 . The mirror unit  221  ends the read-in-copy process. 
     (S 98 ) The mirror unit  221  transmits a notification indicating that the data is normally read from the copy destination disk to the host device  400 . The mirror unit  221  ends the read-in-copy process. 
       FIGS. 15A to 15C  are diagrams illustrating an example of the write-in-copy process according to the second embodiment. The HDD  320  is a newly introduced HDD as a replacement.  FIG. 15A  illustrates a case where the copy process is performed after the normal write process is performed. Areas  312  and  322  are areas where data is written through the normal write process by the mirror unit  221 .  FIG. 15A  illustrates that areas (hereinafter, referred to as non-write areas) in which data is not yet written and write completion areas coexist in the areas of the logical volumes  310   a  and  320   a . For example,  FIG. 15A  illustrates that the areas  311  and  321  are non-write areas. For example,  FIG. 15A  illustrates that the areas  312  and  322  are write completion areas. 
     The HDD  310  is the copy source disk. The HDD  320  is the copy destination disk. The copy unit  222  performs the copy process. The copy unit  222  copies data stored in write completion areas among the areas of the logical volume  310   a  to the logical volume  320   a  by referring to the write area management table  212 . 
     The mirror unit  221  receives a write request from the host device  400  during the copy process. The mirror unit  221  writes data in the areas  311  and  321 . 
       FIG. 15B  illustrates that an error occurs when the mirror unit  221  writes the data in the area  311 .  FIG. 15B  illustrates that no error occurs when the mirror unit  221  writes the data in the area  321 . The copy unit  222  excludes data stored in the area  311  from the copy-target data (Yes in S 42 ). 
       FIG. 15C  illustrates that the copy process is completed. The configuration management unit  223  separates the HDD  310  from the mirroring configuration (S 52 ). The configuration management unit  223  registers “INVALID” in the item of the disk state in the mirror disk management table  211  corresponding to the HDD  310 . The configuration management unit  223  registers “ACTIVE” in the item of the disk state in the mirror disk management table  211  corresponding to the HDD  320 . The HDD  310  is an operation disk. The HDD  320  is an operation disk. 
     According to the second embodiment, the CM  200  excludes data corresponding to an error area from the copy-target data in the data copy to prevent indefinite data from being copied from the copy source disk to the copy destination disk. 
     As a result, the CM  200  prevents the copy destination disk from being a state in which data is not guaranteed. Since the CM  200  normally writes the write data of the write request instead of the data excluded from the copy-target data, the copy destination disk may be used as a storage device in which data is guaranteed. 
     Therefore, the CM  200  may guarantee data in the copy destination disk even when an error occurs in the copy source disk during the copy process. 
     According to the second embodiment, since the CM  200  excludes non-write areas from the copy-target data during the copy process, the CM  200  may shorten time spent on the copy process. 
     According to the second embodiment, when the CM  200  receives a write request to write data in an error area in the logical volume  310   a  during the copy process, the CM  200  writes the data in an area of the logical volume  320   a  corresponding to the error area in the logical volume  310   a . As described above, the CM  200  may write data in the copy destination disk (HDD  320 ) while continuously performing the copy process even when an error occurs in the copy source disk (HDD  310 ). Further, the CM  200  may store latest data in the copy destination disk. 
     According to the second embodiment, when the CM  200  receives a read request to read data from an error area in the logical volume  310   a  during the copy process, the CM  200  reads data from an area of the logical volume  320   a  corresponding to the error area in the logical volume  310   a . As described above, the CM  200  may read data from the copy destination disk (HDD  320 ) even when an error occurs in the copy source disk (HDD  310 ). 
     The information processing in the first embodiment may be implemented by causing a processor in the information processing device  2  to execute a program. The information processing in the second embodiment may be implemented by causing the CPU  201  to execute a program. The program may be written in a computer-readable recording medium. 
     For example, the program may be distributed by circulating the computer-readable recording medium having stored therein the program. A program that implements a function equivalent to the control unit  220  may be set as a separate program to separately distribute each program. The function of the control unit  220  may be implemented by a separate computer. The computer may, for example, store the program stored in the recording medium in the RAM  202  or the flash memory  203 , and read and execute the program. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to an illustrating of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.