Abstract:
A method for displaying a state of a copy pair which is a pair of logical volumes belonging to one or a plurality of storage sub systems connected to a task server, including: monitoring periodically, by a backup management program on the task sever, an operation condition of an application on the task server; notifying, by the backup management program, a maintenance to a control program on the storage sub system, if the application is on a stop condition at some time; setting, by the control program which receives the notification, “on-maintenance” to an action mode on the storage sub system; after a maintenance by a user and at time of a restart of the application, checking, by the backup management program, the operation condition of the application and notifying a release of the maintenance to the control program; and setting, by the control program which receives the notification of the release, the action mode of the storage sub system to a normal condition.

Description:
CROSS-REFERENCE TO PRIOR APPLICATION 
       [0001]    This is a continuation of U.S. application Ser. No. 11/431,711, filed May 11, 2006. This application relates to and claims priority from Japanese Patent Application No. 2006-070181, filed on Mar. 15, 2006. The entirety of the contents and subject matter of all of the above is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a technology for displaying the pair state of a copy pair in one or a plurality of storage systems. 
         [0004]    2. Description of the Related Art 
         [0005]    For example, Japanese Patent Application Laid-Open No. 2004-264973 discloses a technology for copying data from a primary logical volume to a secondary logical volume which are paired. In to this patent application, the pair states of a plurality of volume pairs and the pair state of each volume pair are displayed in a list, as shown in  FIG. 5 . 
         [0006]    Incidentally, a logical volume configuring a volume pair exists in one or a plurality of storage subsystems connected to a host computer. One logical volume and other logical volume may exist in a single storage subsystem or in separate storage subsystems. 
         [0007]    As a configuration in which a plurality of volume pairs are used, the following configurations, for example, are possible. Specifically, possible are, for example, a configuration in which a copy group is obtained by synchronizing a plurality of volume pairs (see  FIG. 1A ), a configuration in which the primary logical volumes (referred to as “PVOL” hereinafter) of two volume pairs are the same (see  FIG. 1B ), and a configuration in which one secondary logical volume (referred to as “SVOL” hereinafter) and a PVOL are the same volume (see  FIG. 1C ). 
         [0008]    In the case of such configurations of a copy group, even when employing a method of displaying the pair states of a plurality of volume pairs and the pair state of each volume pair in a list (see  FIG. 2A , for example), a user viewing a screen displaying the list cannot understand whether the configuration using a plurality of volume pairs exists or not. 
         [0009]    Therefore, as a method for solving such a problem, a method of displaying a pair state of an abstracted copy group, as shown in  FIG. 2B , can be employed. In  FIG. 2B , for example, at least one volume pair within a copy group, “G_DF600_SI”, is in a pair state of “sync”. 
         [0010]    Furthermore, as another method, as shown in  FIG. 2C , for example, a method of displaying a configuration of a plurality of volume pairs and a pair state of each volume pair can be employed.  FIG. 2C  shows a configuration of the example shown in  FIG. 1C , and, as can be seen in the figure, the volume pair on the first row is in a pair state of “split” and the volume pair in the second row is in a pair state of “sync”. 
         [0011]    As yet another method, a method of combining the display methods of  FIG. 2B  and  FIG. 2C  can be employed. Specifically, for example, as shown in  FIG. 2D , a method of displaying a configuration consisting of a plurality of copy groups (for example, copy groups specified by a user) and a pair state of each copy group on a screen can be employed. According to  FIG. 2D , for example, the pair state of a first copy groups is “sync”, the pair state of a second copy group is “split”, and the pair state of a third copy group is “resync”. According to  FIG. 2D , each SVOL of the first copy group is integrated with each PVOL of the second copy group and of the third copy group. 
         [0012]    However, even if any of the above-described methods is employed, at least the following three problems cannot be solved. Each of the problems is described hereinafter. It should be noted that a volume pair is referred to as “copy pair”. Further, a pair state which is not intended by a user is referred to as “involuntary state”, and, out of the involuntary pair states, an involuntary state which is required to be processed in any way (for example, a pair state which is changed due to detection of a hard error or soft error) is referred to as “error state”. 
         [0013]    (1) Change of pair state, which is performed intentionally by the user, cannot be distinguished from other changes of pair states. 
         [0014]    For example, when a copy pair of local copies (local copy is performed inside a single storage subsystem) is used, a user sometimes has to intentionally change the pair state of the copy pair in order to acquire a backup of data. Normally, change of pair state performed intentionally by the user should be distinguished from change of a pair state which is performed involuntarily by the user due to some kind of problems. 
         [0015]    However, in the above display method, although a pair state is displayed on a display screen, it is not possible to distinguish, only by looking, whether the pair state is the one which is changed by an operation performed intentionally by the user. For this reason, the user cannot determine whether the pair state displayed on the screen is an intended result or an involuntary state which is not an intended result, and consequently has to distinguish the presence of a problem by collating an execution condition of the operation performed by the user himself with the displayed information. 
         [0016]    (2) In the case where a number of copy pairs are in the error state, the scope of the occurrence of the error state is difficult to be comprehended. 
         [0017]    Sometimes thousands of copy pairs exist in a single storage subsystem. All of these copy pairs or some batches of copy pairs are sometimes brought into the error state simultaneously, depending on the type of failure. For example, suppose that, in the case where thousands of copy pairs of remote copies (remote copy is performed in the case where a PVOL exists in a storage subsystem and a SVOL exists in other storage subsystem) are used, a failure occurs in a communication medium (for example, a cable or a switch) between the storage subsystems. In this case, all of the copy pairs (that is, copy pairs containing logical volumes into or from which data is input or output via the ports) that use the ports connected to the communication medium are brought into the error state due to this failure. 
         [0018]    However, in the above display method, although the user can understand that the numbers of copy pairs are brought into the error state, since the displayed pair states of the numbers of copy pairs are changed to the error state, the user cannot take a panoramic view of the entire scope of the occurrence of the error state because the pair states are displayed in a copy pair unit or a copy group unit. For this reason, the user has to comprehend the entire scope of the occurrence of the error state by confirming the all copy pairs brought into the error state. Moreover, when displaying a number of pair states on the display screen and concurrently updating these numbers of pair states to the error state, there is a problem that it requires a long time to perform rendering of the screen, which is associated with updating of the information. 
         [0019]    (3) When it is uncertain whether the pair state is the error state or not, the detailed information required for making determination is difficult to be comprehended. 
         [0020]    A state to be detected as a pair state is changed to not only a pair state due to the above mentioned hard error, but also to a pair state due to an erroneous operation performed by the user. The erroneous operation performed by the user is not a detectable hard error or soft error, thus even if a pair state is changed by the erroneous operation of the user, the pair state is not displayed as the error state. 
         [0021]    In other words, in the above display method, the user needs to determine whether the changed pair state is in the error state or not. Specifically, for example, in order to determine whether or not the changed pair state is in a state which requires to be processed (i.e. error state), the user has to perform another operation for displaying necessary detailed information and refer to the detailed information displayed by the operation. 
       SUMMARY OF THE INVENTION 
       [0022]    The present invention is contrived in view of the above problems, and an object thereof is to provide a copy pair display method in which a distinction can be made between change of pair state performed intentionally by a user and change of pair state performed involuntarily by the user. 
         [0023]    Another object of the present invention is to provide a copy pair display method in which, when an error state occurs in a number of copy pairs simultaneously, the user can easily comprehend the scope of the occurrence of the error state. 
         [0024]    Yet another object of the present invention will become apparent from the following description. 
         [0025]    In a display method according to a first aspect of the present invention: a user request, which is a request complying with an intentional operation performed on a host computer by a user, is transmitted to a storage system by the host computer; the storage system which receives the user request records on a storage region (memory, for example) thereof user operation information, which is information related to the user request, and changes, in copy pair management information in which is recorded, for each copy pair, a subsystem pair state which is a pair state in the storage system, a subsystem pair state of a copy pair related to the user request to a subsystem pair state accompanied with the user request; using the user operation information and the copy pair management information after update, a distinction is made between a user-operated copy pair, which is in the subsystem pair state changed in accompany with the user request complying with user operation performed intentionally by the user, and a user-unoperated copy pair which is not in the subsystem pair state; and, on the basis of a result of the distinction, a pair state for display of the user-operated copy pair and a pair state for display of the user-unoperated copy pair are displayed in different display modes respectively. 
         [0026]    In a first embodiment, the user operation may be a backup/restore operation for backing up or restoring data inside a logical volume in which data used by the host computer is stored. 
         [0027]    In the second embodiment according to the first embodiment, the user request may be a backup/restore request complying with the backup/restore operation. The user operation information is information indicating that backup or restoration is being executed for a copy pair complying with the backup/restore request, and may be stored in the storage region while the backup or restoration is being executed. 
         [0028]    In a third embodiment, the user operation may be a subsystem state operation for bringing a storage system state desired by the user to a state desired by the user. The user operation information may be subsystem state information which indicates that the storage system is brought into a state complying with the user request. 
         [0029]    In a fourth embodiment according to the third embodiment, the user operation further includes a backup/restore operation for backing up or restoring data inside a logical volume in which data used by the host computer is stored, and, in such a case, the user operation information may be execution condition information indicating that backup or restoration is being executed for a copy pair complying with the backup/restore request. The display form of the pair state for display of the user-operated copy pair can be made different in accordance with whether the user operation information is the subsystem state information or the execution condition information. 
         [0030]    In a fifth embodiment according to the fourth embodiment, when the user operation information is the subsystem state information, a subsystem display object, which is an object representing the storage system, and a first user operation display object, which is an object indicating that the storage system is in a state complying with the user operation, can be associated with each other and displayed, and, in a meanwhile, when the user operation information is the execution condition information, a user-operated pair display object, which is an object related to the user-operated copy pair, and a second user operation display object, which is an object indicating that the user operated-copy pair is in a state complying with the user operation, can be associated with each other and displayed. In this case, the first and second user operation display objects are in the pair state for display of the user-operated copy pair. 
         [0031]    In a sixth embodiment, an information element representing one or a plurality of types of subsystem elements of the storage system may be related to the updated copy pair management information for each copy pair. Error specifying information for specifying an error occurrence area in the storage system can be acquired from the storage subsystem, and the error occurrence area in the storage system can be detected from the error specifying information. Furthermore, the user-unoperated copy pair, which is associated with the same subsystem element as the detected error occurrence area, can be specified from the updated copy pair management information, and the pair states for display of one or more of the specified user-unoperated copy pairs associated with the same error occurrence area can be displayed in units of the error occurrence area. 
         [0032]    In a seventh embodiment according to the sixth embodiment, the error occurrence area may be a communication port existing on an access path to one of the user-unoperated copy pair or other logical volume. The subsystem pair state of the user-unoperated copy pair, which is associated with the communication port, may be updated to an error at the storage system having the communication port, by the occurrence of an error at the communication port. A port display object, which is an object representing the communication port of the error occurrence area, and an error display object, which is an object representing the error, can be associated with each other and displayed. 
         [0033]    In an eighth embodiment according to the sixth embodiment, the error occurrence area may be a common storage resource which is used by the user-unoperated copy pair. A subsystem pair state of the user-unoperated copy pair, which is related to the common storage resource, may be updated to an error at the storage system having the common storage resource, by the occurrence of an error at the common storage resource. A common resource display object, which is an object representing the common storage resource of the error occurrence area, and an error display object, which is an object representing the error, can be associated with each other and displayed. 
         [0034]    In a ninth embodiment according to the sixth embodiment, the error occurrence area may be a specific hardware in the storage system other than the communication port existing on the access path to one of the user-unoperated copy pair or other logical volume. A subsystem pair state of the user-unoperated copy pair, which is related to the storage system with the hardware, may be updated to an error at the storage system having the hardware, by the occurrence of an error at the hardware. A subsystem display object, which is an object representing the storage system having the hardware of the error occurrence area, and an error display object, which is an object representing the error, can be associated with each other and displayed. 
         [0035]    In a tenth embodiment according to the sixth embodiment, an error area display object, which is an object representing the error occurrence area, and an error display object, which is an object displaying an error, can be associated with each other and displayed. When the error display object is designated by the user, detailed information comprising at least one user-unoperated copy pairs related to the error occurrence area, and the pair state for display and/or a subsystem pair state of each user-unoperated copy pair can be displayed. 
         [0036]    In an eleventh embodiment according to the sixth embodiment, the pair state for display of the user-unoperated copy pair can be determined on the basis of the subsystem pair state of the user-unoperated copy pair. 
         [0037]    In a twelfth embodiment according to the eleventh embodiment, on the basis of the subsystem pair state of the user-unoperated copy pair and other type of information of the user-unoperated copy pair, the pair state for display can be determined as a normal state representing a state requiring no particular processing if the subsystem pair state is an expected subsystem pair state, the pair state for display can be determined as an error state representing a state in which an error occurs and which thus requires to be processed in any way if the subsystem pair state is an error, and, for the user-unoperated copy pairs in other conditions, the pair states for display can be determined as a warning state representing a state in which no error occurs but some processing needs to be performed. 
         [0038]    In a thirteenth embodiment according to the twelfth embodiment, a user-unoperated pair display object, which is an object related to the user-unoperated copy pair in which the pair state for display is determined as the warning state, and a warning display object, which is an object representing the warning state, can be associated with each other and displayed. When the warning display object is designated by the user, detailed information related to the user-unoperated copy pair and specified from the updated copy pair management information can be displayed. 
         [0039]    In the display method according to a second aspect of the present invention: a storage system holds copy pair management information in which is recorded, for each copy pair, a subsystem pair state which is a pair state in the storage system, the copy pair management information being associated with an information element representing one or a plurality of types of subsystem elements of the storage system, for each copy pair; error specifying information for specifying an error occurrence area in the storage system can be acquired from one storage subsystem or each of a plurality of the storage systems, to detect the error occurrence area in the storage system from the error specifying information; and a copy pair, which is associated with the same subsystem element as the detected error occurrence area, is specified from the copy pair management information, to display, in units of the error occurrence area, the pair states for display of one or more of the specified copy pairs associated with the same error occurrence area. 
         [0040]    In a first embodiment, the pair state for display of the copy pair can be determined on the basis of the subsystem pair state of the copy pair. 
         [0041]    In a second embodiment according to the first embodiment, on the basis of the subsystem pair state of the copy pair and other type of information of the copy pair which is specified from the copy pair management information, if the subsystem pair state is an expected subsystem pair state the pair state for display can be determined as a normal state representing a state requiring no particular processing, if the subsystem pair state is an error the pair state for display can be determined as an error state representing a state in which an error occurs and which thus requires to be processed in any way, and, for the copy pairs in other conditions, the pair states for display can be determined as a warning state representing a state in which no error occurs but some processing needs to be performed. 
         [0042]    In a third embodiment according to the second embodiment, an object related to the copy pair in which the pair state for display is determined as the warning state, and a warning display object, which is an object representing the warning state, can be associated with each other and displayed. When the warning display object is designated by the user, detailed information related to the copy pair and specified from the copy pair management information can be displayed. 
         [0043]    A display device according to a third aspect of the present invention is configured such that a user request, which is a request complying with an intentional operation performed on a host computer by a user, is transmitted to a storage system by the host computer, and that the storage system which receives the user request records on a storage region thereof user operation information, which is information related to the user request, and changes, in copy pair management information in which is recorded for each copy pair a subsystem pair state which is a pair state in the storage system, a subsystem pair state of a copy pair related to the user request to a subsystem pair state accompanied with the user request, the display device comprising: an acquisition portion for acquiring the user operation information and the copy pair management information after update from a storage subsystem; a distinction portion for making a distinction between a user-operated copy pair, which is in the subsystem pair state changed in accompany with the user request complying with user operation performed intentionally by the user, and a user-unoperated copy pair which is not in the subsystem pair state, by using the acquired user operation information and updated copy pair management information; and a display portion for providing a screen for displaying, on the basis of a result of the distinction, a pair state for display of the user-operated copy pair and a pair state for display of the user-unoperated copy pair, in different display modes respectively. 
         [0044]    In the display device according to a fourth aspect of the present invention, the storage system holds copy pair management information in which is recorded, for each copy pair, a subsystem pair state which is a pair state in the storage system, the copy pair management information being associated with an information element representing one or a plurality of types of subsystem elements of the storage system, for each copy pair, the display device comprising: a first acquisition portion for acquiring the copy pair management information from each of storage subsystems; a second acquisition portion for acquiring, from the storage subsystems, error specifying information for specifying an error occurrence area in the storage system; a detection portion for detecting the error occurrence area in the storage system from the acquired error specifying information; and a display portion for providing a screen for specifying a copy pair, which is associated with the same subsystem element as the detected error occurrence area, from the copy pair management information, and displaying, in units of the error occurrence area, the pair states for display of one or more of the specified copy pairs associated with the same error occurrence area. 
         [0045]    The above-described display device may be, for example, a server machine, a host computer, or a device provided in a storage system. The processing performed in the above-described display method and display device can be executed by predetermined parts. The parts can be rephrased to “means”. The parts or means can be realized by a hardware (a circuit, for example), a computer program, or a combination thereof (for example, one or a plurality of CPUs for reading and executing a computer program). Each computer program can be read from a storage resource (memory, for example). The storage resource can be installed via a recording medium such as a CD-ROM or DVD (Digital Versatile Disk), or can be downloaded via a communication network such as the Internet or LAN. The database management system described above can be taken as a computer program. Furthermore, the database management system described above can be mounted on a storage subsystem or on a host computer controlling the storage subsystem. 
         [0046]    According to the display method related to the first aspect of the present invention and the display device related to the third aspect of the present invention, display can be performed so that a distinction can be made between intentionally change of a pair state performed by a user or involuntary change of a pair state. 
         [0047]    According to the display method related to the second aspect of the present invention and the display device related to the fourth aspect of the present invention, a display can be performed so that the user can easily comprehend the scope of the occurrence of the error state in the case where the error state occurs simultaneously on a number of copy pairs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0048]      FIG. 1A  is an explanatory diagram of a copy group: 
           [0049]      FIG. 1B  shows an example of a configuration of a volume pair; 
           [0050]      FIG. 1C  shows another example of the configuration of the volume pair; 
           [0051]      FIG. 2A  shows an example of conventional display of a copy pair; 
           [0052]      FIG. 2B  shows an improved example of the conventional display of the copy pair; 
           [0053]      FIG. 2C  shows another improved example of the conventional display of the copy pair; 
           [0054]      FIG. 2D  shows yet another improved example of the conventional display of the copy pair; 
           [0055]      FIG. 3  shows a hardware configuration example of the entire system according to an embodiment of the present invention; 
           [0056]      FIG. 4  shows a software configuration example of the entire system according to an embodiment of the present invention; 
           [0057]      FIG. 5  shows an example of a flow of processing performed by a backup management program  71 ; 
           [0058]      FIG. 6  shows a schematic example of a flow of processing performed by a storage monitoring program  63  before displaying a copy pair; 
           [0059]      FIG. 7  shows an example of a flow of concrete processing in S 250  of  FIG. 6 ; 
           [0060]      FIG. 8  shows an example of a flow of concrete processing in S 300  of  FIG. 6 ; 
           [0061]      FIG. 9  shows an example of a flow of concrete processing in S 350  of  FIG. 6 ; 
           [0062]      FIG. 10  shows an example of a flow of concrete processing in S 400  of  FIG. 6 ; 
           [0063]      FIG. 11A  shows an example of a backup/restore execution condition table  77  in S 40  of  FIG. 5 ; 
           [0064]      FIG. 11B  shows a configuration example of a display copy pair state table  67 ; 
           [0065]      FIG. 11C  shows a configuration example of a pair state priority table  69 ; 
           [0066]      FIG. 12A  shows an example of a copy pair state table  65  in S 200  of  FIG. 6 ; 
           [0067]      FIG. 12B  shows an example of the copy pair state table  65  at the point of time when S 254  of  FIG. 7  is completed; 
           [0068]      FIG. 13A  shows an example of the copy pair state table  65  at the point of time when S 257  of  FIG. 7  is completed; 
           [0069]      FIG. 13B  shows an example of the copy pair state table  65  at the point of time when the processing of  FIG. 8  is completed; 
           [0070]      FIG. 14A  shows an example of the copy pair state table  65  in the case where the volume pool capacity becomes inadequate in S 357  of  FIG. 9 ; 
           [0071]      FIG. 14B  shows a display example of a monitor screen  61  in the case where all copy groups as the targets of monitoring are determined as “normal”; 
           [0072]      FIG. 15A  shows a display example of the monitor screen  61  in the case where there exists a copy pair in the copy groups, which is determined as “warning”, the copy groups being targets of monitoring; 
           [0073]      FIG. 15B  shows a display example of the monitor screen  61  in the case where an error occurs at a communication port for performing remote copy; 
           [0074]      FIG. 15C  shows a display example of the monitor screen  61  in the case where an error occurs at a storage subsystem  31 ; 
           [0075]      FIG. 16A  shows a display example of the monitor screen  61  in the case where there exist a copy pair in the copy groups as the targets of monitoring, which is determined as “normal”, and a copy pair determined as “backup/restoration being executed”; 
           [0076]      FIG. 16B  shows a display example of the monitor screen  61  in the case where an operation mode of the storage subsystem having the copy groups, which are the targets of monitoring, is “under maintenance”; 
           [0077]      FIG. 17  shows a configuration example of a copy pair management table held in a storage subsystem  31 A; 
           [0078]      FIG. 18A  shows a first display example of the monitor screen  61  in the case where data related to three or more storage subsystems is registered in the copy pair state table; 
           [0079]      FIG. 18B  shows a second display example of the monitor screen  61  in the above case; 
           [0080]      FIG. 18C  shows third display example of the monitor screen  61  in the above case; and 
           [0081]      FIG. 18D  shows a fourth display example of the monitor screen  61  in the above case. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0082]      FIG. 3  shows a hardware configuration example of the entire system according to an embodiment of the present invention. It should be noted in  FIG. 3  that a set of a common main number and an individual sub-character (for example,  11 A,  11 B) is applied to the like elements. Hereinafter, when distinguishing between the like elements explanation is provided using the main numbers only, and, when distinguishing between the like elements explanation is provided using the set of a main number and a sub-character. The same is applied for the other figures. 
         [0083]    For example, a client terminal  1 , at least one task server  11  (two task servers  11 A and  11 B, hereinafter), and a monitoring server  51  are connected to a first communication network  10 . Furthermore, the plurality of task servers  11 A and  11 B, the monitoring server  51 , and at least one storage subsystem  31  (two storage subsystems  31 A and  31 B, hereinafter) are connected to a second communication network  20 . The first communication network  10  is a network, such as LAN (Local Area Network), for performing communication in accordance with, for example, a TCP/IP (Transmission Control Protocol/Internet Protocol). On the other hand, the second communication network  20  is a network, such as SAN (Storage Area Network), for performing communication in accordance with, for example, FC (Fiber Channel) protocol. The first communication network  10  and the second communication network  20  may be a single network. 
         [0084]    The client terminal  1  is a type of computer and can comprise, for example, a CPU  3 , a storage resource  5 , a port  9  which can be connected to the first communication network  10 , and a display device  7 . The storage resource  5  is, for example, a memory and/or auxiliary storage device (for example, a hard disk drive (“HDD” hereinafter)). The storage resource  5  can store data and a plurality of types of computer programs. The CPU  3  can read and execute computer programs. Hereinafter, for clarity of explanation, the main body of the processing performed by reading and executing the computer programs by means of the CPU is sometimes performed by the computer program instead of the CPU. 
         [0085]    The task server  11  also is a type of computer and can comprise, for example, a CPU  13 , a storage resource  15 , a port  18  which can be connected to the first communication network  10 , and a port  19  which can be connected to the second communication network  20 . 
         [0086]    The monitoring server  51  also is a type of computer and can comprise, for example, a CPU  54 , a storage resource  55 , a port  52  which can be connected to the first communication network  10 , and a port  53  which can be connected to the second communication network  20 . 
         [0087]    The storage subsystem  31  comprises a plurality of disk devices (for example, a HDD, or may be other type of physical storage devices)  37 , and a control device  34  for controlling access to the disk devices. The control device  34  comprises, for example, a plurality of ports (only one port is shown in  FIG. 3 )  32  which can be connected to the second communication network  20 , a plurality of ports (only one port is shown in  FIG. 3 )  36  which can be connected to the disk devices  37 , a CPU  33 , and a memory  35 . 
         [0088]    In the above configurations, at least one of the client terminal  1 , monitoring server  51 , task server  11 A and  11 B, and storage subsystems  31 A and  31 B may be virtually created (i.e. as so-called “virtual computer”) in a single device. Moreover, the configuration of the control device  34  described above is an example, but other configuration can be employed. For example, instead of being configured as above, at least one of the control devices  34 A and  34 B can be configured so as to comprise a plurality of first control portions (control circuit boards, for example) for controlling communication with external devices (for example, servers or storage subsystems other than the first control portions), a plurality of second control portions (for example, control circuit boards) for controlling communication with the disk devices, a cache memory which can store data communicated between the external devices and the disk devices, a control memory which can store data for controlling the storage subsystems (the cache memory and the control memory do not have to be different memories), and a connection portion (for example, a switch such as a crossbar switch) for connecting each of the first control portions, each of the second control portions, the cache memory, and the control memory. In this case, the processing of the control device  34  can be carried out by either one of the first and second control portions or by collaboration thereof. 
         [0089]      FIG. 4  shows a software configuration example of the entire system according to an embodiment of the present invention. 
         [0090]    The client terminal  1  is a host as a terminal for monitoring a copy pair. On the display device  7  of the client terminal  1 , a monitor screen  61  for displaying information collected by a storage monitoring program  63  described hereinafter is displayed. It should be noted in the present embodiment that the monitor screen  61  is provided by a browser (a WEB browser, for example) or may be an application developed by Java® or the like. 
         [0091]    The task server  11  is a server for executing a task of a user. In the task server  11 , an application program (“application” hereinafter)  73  used in a task of the user and a backup management program  71  which is a computer program for backup management are operated. 
         [0092]    The application  73  is a computer program for executing a task of the user. The application  73  can read data recorded in logical volumes  78 (PVOL  78 P, for example) prepared in the storage subsystem  31 , and write data into the logical volumes  78 . It should be noted in the present embodiment that although the applications  73 A,  73 B are operated on the task servers  11 A,  11 B respectively, as long as there is one application, the number of the applications is not limited. 
         [0093]    The backup management program  71  can control a volume copy pair provided in the storage subsystem  31 , staticize or cancel staticization of the application  73 , and back up and restore data used by the application  73 . The program  71  comprises a schedule function, can execute regular backup, and, at that moment, can successively record information indicating an execution condition of backup or restoration, in a storage region inside the storage subsystem  31  via a control program  75  inside the storage subsystem  31 . In order to perform backup in units of the logical volume, the program  71  further holds the relationship between each application  73  and the logical volume used by the each application  73  (for example, an ID of the application  73  and an ID of the logical volume  78  used by the application  73 ), as a volume management table (not shown). 
         [0094]    The monitoring server  51  is a server for monitoring the storage subsystem  31 , and the storage monitoring program  63  is installed on the monitoring server  51 . In the storage resource  55  of the monitoring server  51 , not only the storage monitoring program  63 , but also a copy pair state table  65 , a display copy pair state table  67 , and a pair state priority table  69  are stored. These various tables are described hereinafter. It should be noted in the present embodiment that although the monitoring server  51  and the task server  11  are separate devices, the monitoring server  51  and the task server  11  may be integrated. 
         [0095]    The storage monitoring program  63  is a program for monitoring a duplication condition of the logical volumes  78 . The storage monitoring program  63  regularly can acquire a pair state for each copy pair from the control program  75  inside the storage subsystem  31 , process the acquired pair state, and display the copy pair state on a GUI screen of a client. Moreover, in a similar manner, the storage monitoring program  63  can acquire an operation mode of the storage subsystem  31 , a usage condition of a common resource of a copy pair, and an execution state recorded in a backup/restore execution condition table  77  recorded in the memory  35  (or may be other storage region) inside the storage subsystem  31 , and can further receive SNMP (Simple Network Management Protocol) trap information issued from the storage subsystem  31 . 
         [0096]    The storage subsystem  31  comprises the control program  75 , the backup/restore execution condition table  77 , and the plurality of logical volumes  78 . 
         [0097]    The control program  75  is a program for performing control on the logical volumes  78  according to a request from the task server  11  and providing various information recorded in the storage region of the storage subsystem  31 . Specifically, for example, the program  75  can create a snapshot of data on a SVOL and record an execution condition in backup or restoration on the backup/restore execution condition table  77  by splitting and resynchronizing a copy pair in accordance with a request from the backup management program  71 . Moreover, for example, the program  75 , complying with to a request from the storage monitoring program  63 , can notify the monitoring server  51  of the latest copy pair state, an operation mode of the storage subsystem  31 , a usage condition of the common storage resource of the copy pair, and a backup/restore execution condition. 
         [0098]    The logical volumes  78  are logical storage devices created using the storage regions provided by the plurality of grouped disk devices  37  in accordance with, for example, the principle of RAID (Redundant Array of Independent (or Inexpensive) Disks). In the present embodiment, as the types of the logical volumes  78 , there are PVOL  78 P, SVOL  78 S, and JNLVOL  78 J. There is also a volume pool  78 G in which the plurality of logical volumes are grouped together. 
         [0099]    The PVOL  78 P stores data used by the application  73 . If there is a data write request from the application  73 , data is written to the volume  78 P via the control program  75 . Reading of data is performed in the same route. 
         [0100]    The SVOL  78 S can store data inside the PVOL  78 P. For example, the SVOL  78 S holds, as backup data, a snapshot image which is obtained at the time when a copy pair is split due to a request from the backup management program  71 . It should be noted in the present embodiment that the volume  78 S is a virtual volume created by the control program  75 , and the actual data may be stored in the logical volumes  78  configuring the volume pool  78 G. Furthermore, as shown in  FIG. 4 , the data inside the PVOL  78 P may be stored in the SVOL  78 S via, for example, a plurality of the JNLVOL  78 J. 
         [0101]    The volume pool  78 G is a volume group as an entity of virtual volume storing a snapshot image. Since the volume group  78 G is virtualized as a duplicate volume by the control program  75 , the volume group  78 G is not recognized in the processing performed in the task server  11 . However, actually the differential data for holding a snapshot is stored in the volume group  78 G. The user can efficiently utilize the volumes by acquiring a snapshot of data using the virtual volume, as compared to the case of acquiring a duplicate using an actual volume. Without using this method, for example, a snapshot may be acquired using the actual volume instead of the virtualized volume. 
         [0102]    The JNLVOL  78 J is a volume in which is recorded information representing a write history in the PVOL  78 P (“journal” hereinafter). Each journal has, for example, data after update and an updated sequential order. The JNLVOL  78 J is a temporal cache region which is sued for ensuring a sequential order for writing data into copy pairs inside the same copy group when performing asynchronous remote copy. At the point of time when the application  73  writes data into the PVOL  78 P, a corresponding journal is created by the control program  75 A and written into a JNLVOL  78 J 1 . Thereafter, the journal is acquired by a JNLVOL  78 J 2  by a remote control program  75 B (or may be a local control program  75 A) in chronological order, and reflected in the SVOL  78 S inside the acquired journal. The journal is deleted from the JNLVOL  78 J when data transfer is completed (or when data reflection in the SVOL  78 S is completed). It should be noted in the present embodiment that although the JNLVOL is used as a primary cache region, a predetermined storage area (“side file” hereinafter) provided in the memory  35 A may be used as the primary cache region, and asynchronous remote copy may be performed from the side file. In this case, transfer of the data accumulated in the side file may be performed by the local control program  75 A. Moreover, not only the asynchronous remote copy but also synchronous remote copy (for example, copy which is performed such that data written into the PVOL  78 P is transferred from the storage subsystem  31 A to  31 B and written into the SVOL  78 S, without using the JNLVOL or side file) may be performed. 
         [0103]    The above explanation is the software configuration example of the system related to the present embodiment. Although several types of the logical volumes  78  are described above, not only to these types but also other types may be employed, or the number of the types may be less than the number of above types. Specifically, the characteristic of the present embodiment is in a technology for displaying a pair state of a copy pair, and this technology can be applied to a copy pair having any type of logical volume. 
         [0104]    It should be noted that a pair state of a copy pair is classified broadly into a pair state intended by the user and an involuntary pair state. The involuntary state can be classified into an error state which is a pair state requiring to be processed in any way and an involuntary state which does not require any processing. 
         [0105]    The error state is typically a pair state created when a failure is detected at the hardware level or computer program level. There are illustrative embodiments (1) and (2) of the error state as follows. 
       Illustrative Embodiment (1) 
       [0106]    A state of a copy pair of remote copies, in which a failure is generated in the communication medium (a switch or cable, for example) between the both subsystems, whereby the data can no longer be transferred from the PVOL  78 P to the SVOL  78 S, thus the identity between the data of the SVOL  78 S and the data of the PVOL  78 P can no longer be ensured. 
       Illustrative Embodiment (2) 
       [0107]    A state of a copy pair of local copies, in which the control program  75 A can no longer manage the abovementioned differential data, thus validity of the snapshot data acquired by the SVOL  78 S can no longer be ensured. 
         [0108]    In the above illustrative embodiments, a failure is detected at the hardware level or computer program level, thus the failure can be detected as an error by the control program  75 . 
         [0109]    On the other hand, as the involuntary state which is not the error state, there is an involuntary state created by an erroneous operation of the user. There are illustrative embodiments (i) and (ii) of such an involuntary state as follows. 
       Illustrative Embodiment (i) 
       [0110]    A state of a copy pair of remote copies, in which the copy pair is split by the user, thus the identity between the data of the SVOL  78 S and the data of the PVOL  78 P can no longer be ensured. 
       Illustrative Embodiment (ii) 
       [0111]    A state of a copy pair of local copies, in which the user splits the copy pair without staticizing the application  73  (without causing the application  73  to stop updating the data of the PVOL  78 P), thus validity of the snapshot data acquired by the SVOL  78 S can no longer be ensured. 
         [0112]    In the above two illustrative embodiments, the fact that the pair state has changed can be detected by the control program  75 , but the operation itself is ended normally, thus the change of the pair state cannot be determined as an error by the control program  75 . 
         [0113]    The present embodiment provides (1) a mechanism for enabling to distinguish between change of a pair state performed intentionally by the user and change of pair state performed involuntarily by the user, (2) a mechanism for enabling to easily comprehend the scope of the occurrence of an error state when a number of copy pairs are brought into the error state, and (3) a mechanism for enabling to easily comprehend detailed information required for determination when it is uncertain whether the pair state is the error state or not. Hereinafter, each of the mechanisms are described in detail. It should be noted in the description hereinafter copy groups are connected in the form of a cascade (specifically, each SVOL in a copy group and each PVOL in other copy group are the same volume). Furthermore, suppose that a backup schedule (for example, one or more time of day at which backup should be executed) is set in the backup management program  71 . Moreover, suppose that the backup management program  71  holds, as a volume management table, a volume used by the application program  73  operating on the task server  11  operated by the program  71 . In addition, suppose that a table to which a port ID for a volume of each copy pair and an ID of each of the volumes constituting the copy pairs is stored in each of the storage subsystems  31 . 
         [0114]    (1) A mechanism for enabling to distinguish between change of a pair state performed intentionally by the user and change of pair state performed involuntarily by the user. 
         [0115]    One of the characteristics of this mechanism focuses on that intentional change of a pair state which is performed by the user is carried out by a backup or restore operation and a maintenance operation performed when changing the system configuration. In this embodiment, the storage monitoring program  63  discriminates whether an operation performed by the user is the backup or restore operation or the maintenance operation performed when changing the system configuration, whereby a distinction can be made between change of a pair state which is performed intentionally by the user and change of a pair state performed involuntarily by the user. 
         [0116]    In the case of the backup or restore operation, specifically, for example, the storage monitoring program  63  can specify a copy pair, which is subjected to the backup or restore operation, from the execution condition information which is recorded in the backup/restore execution condition table  77  when the backup management program  71  performs the backup/restore operation, determine whether the pair state of the specified copy pair is a pair state associated with the backup or restore operation, and display the pair state of the copy pair so that the user can determine whether it is the change performed intentionally by the user (for example, whether it is the change associated with the backup or restore operation) on the basis of a result of the above determination. 
         [0117]    In the case of the maintenance operation, specifically, for example, when a request according to the maintenance operation performed when changing the system configuration is received from the task server  11 , the storage subsystem  31  writes information indicating that the operation mode is “maintenance” into the memory  35  (or other storage region), and the storage monitoring program  63  can acquire the information indicating the operation mode of the storage subsystem  31  from the control program  75 , determine, on the basis of the information, whether or not the storage subsystem  31  as a target of monitoring is under maintenance, and display the pair state of the copy pair so that the user can determine whether it is the change performed intentionally by the user (for example, whether it is the change associated with the maintenance operation performed when changing the system configuration) on the basis of a result of the above determination. 
         [0118]    In the above manner, the user can distinguish between the change of a pair state which is performed intentionally by the user and the change of a pair state which is performed involuntarily by the user. When the backup operation or restore operation is performed, the control program  75  can change the pair state of the copy pair, which is a target of operation, to a split mode. Further, when the maintenance operation is performed, the control program  75  can record “under maintenance” of the operation mode on the memory  35 , and reset all of the pair states of the copy pairs that belong to the subsystem which is under maintenance (bring the pair states into, for example, a state in which the split mode and difference are not reflected). 
         [0119]    (2) A mechanism for enabling to easily comprehend the scope of the occurrence of an error state when a number of copy pairs are brought into the error state. 
         [0120]    In the present embodiment, the case in which an error occurs in a number of copy pairs is classified into three patterns below (case A) through (case C), and the error state of a copy pair which is abstracted to the same degree as the scope of the occurrence a failure is displayed on a screen, whereby the user can have a panoramic comprehension of the error occurred in a number of copy pairs. 
         [0121]    (Case A: An Error State Occurs in Units of the Communication Port of Remote Copies) 
         [0122]    A situation in which a failure occurs on a communication path of remote copies when configuring copy pairs of remote copies between the subsystems corresponds to the present case. The storage monitoring program  63  determines whether such a situation corresponds to the present case or not by using the information on change of state performed on the copy pairs, the SNMP trap information issued from the storage subsystem  31 , and the data transfer amount in a remote port, which is acquired from the control program  75  of the storage subsystem  31 . As a result of the determination, if the situation corresponds to the present case, the storage monitoring program  63  displays a screen displaying the pair states of the copy pairs of remote copies in units of the communication port, and, on this display screen, displays a screen showing that all copy pairs, which are related to the communication ports where the error has occurred, are in the error state. It should be noted that the communication ports are the ports connected to the second communication network  20 , but may be ports connected to the disk device  37 . Further, the SNMP trap information includes information elements corresponding to the condition, such as IDs of the communication ports where the error has occurred and ID of the storage subsystems where the error has occurred. 
         [0123]    (Case B: An Error State Occurs in Units of the Common Storage Resource of Copy Pairs) 
         [0124]    A situation in which the common storage resource, which is prepared in the storage subsystem  31  in order to maintain a copy pair of local copies and a copy pair of remote copies, becomes inadequate corresponds to the present case. Here, specific examples of the common storage resource include JNLVOL, which is a cache region for storing transfer data of the remote copy, and a volume pool for storing the differential data (for example, a bitmap representing the difference, or the differential data between the VOLs) for holding a snapshot image of the local copy. The storage monitoring program  63  determines whether such a situation corresponds to the present case or not by using the information on change of state performed on copy pairs, the SNMP trap information issued from the storage subsystem  31 , and the used amount of the common storage resource, which is acquired from the control program  75  of the storage subsystem  31 . As a result of the determination, if the situation corresponds to the present case, the storage monitoring program  63  displays a screen displaying the pair states in units of the storage subsystem, and, on this screen, shows that all copy pairs, which are related to the storage subsystem  31  having the common storage resource where the error has occurred, are in the error state. If the common storage resource of the storage subsystem  31 , which is the target of display, is logically divided, the units in which the pair states are displayed can be taken as units of the logically divided units. 
         [0125]    (Case C: An Error State Occurs in Units of the Hardware of the Storage Subsystem  31 ) 
         [0126]    A situation in which some sort of failure occurs in a physical component configuring the storage subsystem  31  corresponds to the present case. The storage monitoring program  63  determines whether such a situation corresponds to the present case or not by using the information on change of state performed on the copy pair, and the SNMP trap information issued from the storage subsystem. As a result of the determination, if the situation corresponds to the present case, the storage monitoring program  63  displays a screen displaying the pair states in units of the storage subsystem  31 , and, on this display screen, shows that all copy pairs, which are related to the storage subsystem  31  where the failure has occurred, are in the error state. 
         [0127]    In the above manner, when an error such as a hardware failure or a communication failure occurs simultaneously on a number of copy pairs, the user can promptly comprehend the scope of the occurrence of the error. 
         [0128]    (3) A mechanism for enabling to easily comprehend detailed information required for determination when it is uncertain whether the pair state is the error state or not. 
         [0129]    This is the case in which it is uncertain whether the changed pair state is the error state or not when the change of pair state does not correspond to any of (1) and (2) above. Therefore, in the present embodiment, instead of displaying information representing a result of determination on whether the pair state is a normal state or error state, the storage monitoring program  63  displays a target copy pair whose pair state is changed, the state of the copy pair, and the detailed information associated to the copy pair. Accordingly, the user can determine whether the copy pair is the error state or not. However, if all of the information items are displayed forcedly on a single screen, the size of each character to be displayed becomes small due to the excessive amount of information. Thus, an icon indicating a warning is displayed so that a copy pair whose pair state is changed can be viewed easily. When the icon is clicked, a pop-up is displayed, and the target copy pair whose pair state is changed, the pair state of the copy pair, and the detailed information associated with the copy pair and required for determination of the user are displayed on the pop-up. 
         [0130]    In the above manner, the user can promptly confirm the target copy, the pair state of thereof, and the detailed information thereof, regarding the change of pair state for which it is uncertain whether it is the error state or not. 
         [0131]    Hereinafter, the present embodiment is described in detail. 
         [0132]      FIG. 5  shows an example of a flow of processing performed by the backup management program  71 . Hereinafter, the program is designated as  71 A. Further, at least the PVOL of a copy pair exists in the storage subsystem  31 . Hereinafter, an example of backup operation is taken to provide the following explanation, but the same processing is performed for restore operation as well. 
         [0133]    The backup management program  71 A staticizes a target application  73 A (instructs the application  73 A not to issue, for example, at least a write command of data) when performing backup and restoration of data of the application  73 A (Step S 10 ). 
         [0134]    Next, the backup management program  71 A specifies a volume used by the application  73 A from the volume management table that the backup management program  71 A holds (S 20 ). 
         [0135]    Next, the backup management program  71 A requests the control program  75 A inside the storage subsystem  31 A to change or restore the pair state of the copy pair, and thereby acquires a backup of the PVOL used by the application  73 A (S 30 ). Specifically, for example, the backup management program  71 A changes the pair state of the copy pair having the PVOL used by the application  73 A, from “sync” to “split”, and thereby acquires a snapshot of the PVOL. 
         [0136]    Next, the backup management program  71 A requests the control program  75 A to record, on the backup/restore execution condition table  77 A, a list of all copy pairs in which a backup is acquired (S 40 ). In accordance with such a request, the control program  75 A records, on the backup/restore execution condition  77 A, the list of all copy pairs in which a backup is acquired, as shown in, for example,  FIG. 11A . In this table  77 A, the execution condition information representing an execution condition of backup or restoration is recorded. The execution condition information includes, for example, a type of operation (either a backup operation or a restore operation), a target application (an ID of an application in which backup data or restored data is used), start time (time at which backup or restoration is started in response to the backup or restore operation), and a target copy pair (an ID of a copy pair which is the target of operation). For example, the request issued in S 30  includes the ID of the PVOL or the ID of the target application  73 A. The control program  75 A specifies a copy pair having the ID from the copy pair management table of  FIG. 17  which is used for managing the copy pair, and can record, as the execution condition information, the ID of the specified copy pair, time at which backup operation is started, ID of the target application, and backup as the operation type, on the backup/restore execution condition table  77 A (on the copy pair management table, an information element of the configuration information on the copy pair state table, a detailed pair state, or an ID of a volume configuring each copy pair is recorded). 
         [0137]    When a certain time period elapses after carrying out S 40 , the backup management program  71 A inquires of the control program  75 A for the pair state of the target volume (PVOL as the target of backup), and confirms whether the changed pair state received in response to the inquiry is a desired pair state or not (in other words, whether the pair state is changed to a normal state or not) (S 50 ). As a result, if the pair state is not the desired pair state (NO in S 60 ), S 50  is performed again, and, if the pair state is the desired pair state (YES in S 60 ), the backup management program  71 A requests the control program  75 A to delete the list recorded in S 40  from the backup/restore execution condition table  77 A (S 70 ). If the list is deleted by the control program  75 A in response to the request, the backup management program  71 A cancels staticization of the application  73 A (S 80 ). It should be noted that, when the execution condition information is deleted, the control program  75 A may bring the pair state of the copy pair corresponding to the copy pair ID contained in the deleted execution condition information back to the original state (may bring the pair state to the pair state immediately executing the backup or restore operation, for example). 
         [0138]    Through the above processing, when the backup or restore operation is carried out by an intentional operation of the user from the task server  11 A, the execution condition information on backup or restore operation is recorded on the backup/restore execution condition table  77 A, and, when backup or restoration is finished, the execution condition information is deleted. Specifically, whether backup or restoration is being executed or not can be determined on the basis of the presence of the execution condition information. 
         [0139]      FIG. 6  shows a schematic example of a flow of processing performed by the storage monitoring program  63  before displaying a copy pair. It should be noted in this flow that the user can set a copy pair as the target of monitoring in advance. Specifically, the user can select a copy pair that the user wishes to monitor, from a list of copy pairs displayed on the monitor screen  61  on the client terminal  1 . In this case, the storage monitoring program  63  can display all copy pairs (for example, all copy pairs recorded on the copy pair state table which is updated by performing S 100  described hereinafter, in the previous step) that the storage monitoring program  63  recognizes, on the monitor screen  61 . 
         [0140]    The storage monitoring program  63  regularly (or irregularly) collects a configuration and state of a copy pair set to the configuration and state, from the storage subsystem  31  (S 100 ). Specifically, for example, the storage monitoring program  63  acquires the latest state and related configuration information for a copy pair which is the target of monitoring (a copy pair which is set as the target of monitoring by the user) from the control program  75  inside the storage subsystem  31 , and stores the acquired information on the copy pair state table  65 . 
         [0141]    Thereafter, for the processing for initialization, the storage monitoring program  63  sets “uncertain” for the pair states for display of all items registered in the copy pair state table  65 , and sets, as the scope of aggregation, the name of a copy group to which the copy pair belongs (S 150  and S 200 ). An example of the copy pair state table  65  at that moment is shown in  FIG. 12A . The copy pair state table  65  is a table for managing copy pair states, wherein, for example, a pair state, configuration information, and aggregation scope are recorded for each copy pair. The pair state is not only a detailed pair state (a pair state recognized in the storage subsystem  31 ) but also a pair state for display (a pair state displayed on the monitor screen  61 ). What is received from the control program  75  is not the pair state for display but the detailed pair state. The configuration information includes, for example, a copy group (an ID of a copy group to which the copy pair belongs), a port (an ID of a port in a path to PVOL or SVOL in the copy pair), a storage subsystem (an ID of a subsystem having PVOL or SVOL of the copy pair), a common resource (and ID of the common storage resource of the copy pair), and a copy type (remote copy or local copy). The configuration information is information that can be received from the control program  75 , and the control program  75  can acquire the configuration information from the abovementioned copy pair management table (see  FIG. 17 . Recorded in, for example, the memory  35 ) and transmit the configuration information in response to a request from the storage monitoring program  63 . The port ID may be recorded for each subsystem ID. The configurations of the port IDs of the respective storage subsystems may be the same or different from one another. The aggregation scope indicates in which scope the pair state of the copy pair is to be collected and displayed when displaying the copy state of the copy pair. For example, if the aggregation scope is a copy group, pair states are displayed in the units of copy group. 
         [0142]    Next, the storage monitoring program  63  performs processing for eliminating changing of pair state performed intentionally by the user from the targets of monitoring (S 250 ), processing for determining the pair state as any of normal, warning, and error states (S 300 ), processing for setting the aggregation scope in accordance with the conditions of the occurrence of various errors (S 350 ), and processing for computing an aggregated pair states based on the set aggregation scope (S 400 ), and causes the monitor screen  61  to perform display on the basis of a result of these processing. 
         [0143]      FIG. 7  shows an example of a flow of concrete processing in S 250  of  FIG. 6 . 
         [0144]    The processing shown in  FIG. 7  is processing for eliminating changing of pair state performed intentionally by the user from the targets of monitoring. In the present embodiment, elimination from the targets of monitoring means processing performed so that the pair state for display of a copy pair, whose pair state is changed intentionally by the user, does not remain “uncertain”. Accordingly, when determining the pair state in processing of  FIG. 8 , the records of the copy pair whose pair state is changed intentionally by the user are not referred to. Hereinafter, the processing is described in detail. 
         [0145]    The storage monitoring program  63  acquires an operation mode of a target storage subsystem (a subsystem corresponding to each subsystem ID in the configuration information in the copy pair state table  65 ) from the control program  75  (S 251 ). When the maintenance operation is received from the task server  11 , the control program  75  writes an operation mode, “under maintenance”, into the memory  35  so that the operation mode write in the memory  35  can be replied in response to a request made in S 251  by the storage monitoring program  63 . 
         [0146]    If the replied operation mode is “under maintenance” (YES in S 252 ), the storage monitoring program  63  sets, in the copy pair state table  65 , “maintenance” as the pair states for display of all copy pairs belonging to the storage subsystem  31  where “under maintenance” is replied, and sets, as the aggregation scope, the ID of the storage subsystem to which the copy pair belongs (S 253  and S 254 ).  FIG. 12B  shows an example of the copy pair state table  65  at the point of time when S 254  is completed.  FIG. 12B  shows an example of the case in which the storage subsystem having a subsystem ID of “Array-A” is under maintenance. It should be noted that the storage monitoring program  63  may check whether the pair state of all copy pairs belonging to the subsystem under maintenance are pair states which are changed in association with the maintenance operation, and, if a positive check result is obtained, S 253  and S 254  may be executed. 
         [0147]    Thereafter (or when a result in S 252  is NO), the storage monitoring program  63  acquires from the control program  75  a list of copy pairs which are the targets of backup/restore processing (specifically, all of the execution condition information items written in the backup/restore execution condition table  77 ) (S 255 ), and, for all of the copy pairs included in this list, sets “backup/restoration being executed” as the pair states for display on the copy pair state table (YES in S 256 , and S 257 ).  FIG. 13A  shows an example of the copy pair state table  65  at the point of time when S 257  is completed.  FIG. 13A  is a result based on the execution condition table  77  shown in  FIG. 11A , and shows an example of the case in which the copy group ID is “CG-C” and backup is being executed. It should be noted that the storage monitoring program  63  may check whether the pair state of the copy pairs in the execution condition information are pair states which are changed in association with the backup or restore operation, and, if a positive check result is obtained, S 257  may be executed. 
         [0148]      FIG. 8  shows an example of a flow of concrete processing in S 300  of  FIG. 6 . 
         [0149]    The storage monitoring program  63  acquires a pair state for display of a first record on the copy pair state table  65  (S 301 ), and, if the pair state for display is “uncertain” (YES in S 302 ), performs the following processing for the record. 
         [0150]    Specifically, if the detailed pair state is “error” from the record in which the pair state for display is “uncertain” (YES in S 304 ), the storage monitoring program  63  sets “error” for the pair state for display in the record (S 308 ). If the copy type is “local copy” and the detailed pair state is “split” (YES in S 305 ), or the copy type is “remote copy” and the detailed pair state is “sync” (synchronized state) (NO in S 305  and YES in S 306 ), the storage monitoring program  63  sets “normal” for the pair state for display of the record (S 309 ). In other case (NO in S 306 ), the storage monitoring program  63  sets “warning” for the pair state for display (S 307 ). It should be noted that the reason that “normal” is set when the copy type is “local copy” and the detailed pair state is “split” is because it means that the snapshot of PVOL is ensured (in the split state, when PVOL is updated the difference generated by the update is acquired by SVOL). Further, the reason that “normal” is set when the copy type is “remote copy” and the detailed pair state is “sync” (synchronized state) is because remote copy in this embodiment is copy performed for the purpose of disaster recovery, and that data updated to PVOL is remote-copied to SVOL (even if the pair state is the synchronized state, remote copy may be synchronous remote copy in which updated data is transferred in synchronization with update of PVOL, or may be asynchronous remote copy in which updated data asynchronously with update of PVOL). Moreover, the reason that “warning” is set when the result in S 306  is NO is because the pair state is not an expected state. In other words, “normal” is not set only when the result in S 305  is YES or the result in S 306  is YES, and thus can be set as long as the pair state is the expected state. 
         [0151]    The storage monitoring program  63  performs the above processing for all records on the copy pair state table  65  (YES in S 310 ).  FIG. 13B  shows an example of the copy pair state table  65  at the point of time when the processing of  FIG. 8  is completed. 
         [0152]      FIG. 9  shows an example of a flow of concrete processing in S 350  of  FIG. 6 . 
         [0153]    The storage monitoring program  63  holds a history representing whether the SNMP trap information is received or not and acquires information written in the history (S 351 ). The SNMP trap information can be received when, for example, an error is detected in the storage subsystem  31 . 
         [0154]    If it is determined from the information written in the history that the SNMP trap information is received (YES in S 352 ), the storage monitoring program  63  acquires the data transfer amount of the remote port (the port of the subsystem having SVOL), the usage amount of JNLVOL, and the usage amount of the volume pool (and other type of common storage resource, if there is any) from the control program  75  (S 353 ), and performs the following processing (the control program  75  can update the data transfer amount of the remote port, the usage amount of JNLVOL, and the usage amount of the volume pool on the memory  35 , and reply with information thereof recorded on the memory  35 , in response to an inquiry from the storage monitoring program  63 ). 
         [0155]    If the data transfer amount of the remote port is lower than a certain thresholds (YES in S 354 ), the storage monitoring program  63  sets, for the copy pair belonging to a corresponding port, an ID (name, for example) of the remote port which corresponds to the aggregation scope of the copy pair state table (S 355 ). 
         [0156]    If the usage amount of JNLVOL or volume pool is higher than a certain threshold (YES in S 356 ), the storage monitoring program  63  sets, for a copy pair using a corresponding common storage resource (a copy pair specified from the copy pair state table  65 ), an ID (name, for example) of the common storage resource which corresponds to the aggregation scope of the copy pair state table  65  (S 357 ).  FIG. 14A  shows an example of the case where the capacity of the volume pool with an ID “POOL-A” becomes inadequate. It should be noted that YES in S 356  and a step S 357  may not be performed for a snapshot in which the actual volume is used, asynchronous remote copy in which side file is used, or synchronous remote copy. 
         [0157]    In the case other than the above case (NO in S 356 ), for a copy pair stored in a corresponding storage subsystem, the storage monitoring program  63  sets an ID of the corresponding storage subsystem on the aggregation scope of the copy pair state table  65  (S 358 ). 
         [0158]      FIG. 10  shows an example of a flow of concrete processing in S 400  of  FIG. 6 . 
         [0159]    The storage monitoring program  63  secures the display copy pair state table  67  for recording an aggregation state of a copy pair (S 401 ). A configuration example of the display copy pair state table  67  is shown in  FIG. 11B . In this table  67 , a target of display, a pair state, and detailed information (information displayed as detailed information) are recorded. The detailed information is, for example, a copy pair (a copy pair ID), storage subsystem (subsystem ID), and state update time. At the time of S 401 , no information is recorded on the table  67  (that is, each cell on the table is blank). 
         [0160]    Next, the storage monitoring program  63  confirms the information set in the aggregation scope, for the first record on the copy pair state table  65  (S 402 ). 
         [0161]    The storage monitoring program  63  searches for an item registered in the display copy pair state table  67 , and confirms whether the items is already registered in a confirmed aggregation scope or not (S 403 ). In this case, set information is not registered (NO in S 403 ), thus the information set as the aggregation scope is set as the target of display and the pair state for display is set as the pair state respectively in the display copy pair state table  67  (S 407 ). 
         [0162]    The above processing is successively repeated for all copy pairs registered in the copy pair state table  65 , to complete the display copy pair state table  67 . It should be noted at this moment that, if the aggregation scope is already registered in the display copy pair state table  67  in S 403 , the storage monitoring program  63  compares the pair state registered in the display copy pair state table  67  with the pair state for display (the pair state for display on the copy pair state table  65 ) for a corresponding copy pair (a copy pair having the same ID as the copy pair in the detailed information), and registers the one with higher priority as a copy pair state for display, in accordance with the pair state priority table  69  (see  FIG. 11C ) (S 404 , YES in S 405 , S 406 ). According to the pair state priority table  69 , the pair state which is changed by an intentional operation of the user is high on priority (the aggregation scope is wider for “maintenance” than “backup/restoration being execute”, thus the priority for “maintenance” is higher, but the priorities of the both may be reversed). The pair state, which is brought into the error state due to an error detected at the hardware level or computer program level, has the next higher priority. The involuntary state other than the error state has the next higher priority. The priority is lowest when the state is normal. Therefore, for example, if explained using the copy pair state table  65  in  FIG. 14A  as an example, for the aggregation scope of “CG-C”, the copy pair state for display of a copy pair “Pair-D” is acquired as “normal”, where “normal” is written on the display copy pair state table  67 , and then although the pair state for display of a copy pair “Pair-E” is acquired as “warning”, the priority of “warning” is higher than that of “normal” according to the pair state priority table  69 , thus “normal” is updated to “warning” on the display copy pair state table  67 . 
         [0163]    On the above work, when the copy pair state is “warning” or “error” (YES in S 408 ), the storage monitoring program  63  records the detailed information such as the ID of a corresponding copy pair, the ID of a storage subsystem having the copy pair, and the state update time (time at which the state is updated), on the display copy pair state table  67  (S 409 ). It should be noted that although the information recorded on the display copy pair state table  67  shown in  FIG. 11B  is the information recorded using the copy pair state table shown in  FIG. 14A , the state update time can be taken as the time included in the information which is received from the control program  75  in order to construct the copy pair state table shown in  FIG. 14A . Moreover, the detailed information may include information on an element configuring the target of display (in other words, the aggregation scope), in addition to the information on the copy pair corresponding to “error” or “warning”. For example, if the target of display is a copy group, the detailed information may be information related t each of the all copy pairs configuring the copy group (for example, at least one of the ID of the copy pair, the detailed pair state of the copy pair, and the pair state for display of the copy pair). 
         [0164]    Finally, the storage monitoring program  63  displays the states determined as any of “normal”, “warning”, “error”, “backup/restoration being executed”, and “under maintenance”, on the monitor screen  61  on the basis of the display copy pair state table  67  through the above processing. At this moment, each of the determined states can be expressed by different icons. Hereinafter, a display example for each case is described. 
         [0165]    (1) When the pair states for display of all copy pairs are “normal”. 
         [0166]      FIG. 14B  shows a display example of the monitor screen  61  in the case where all copy groups as the targets of monitoring are determined as “normal”.  FIG. 14B  shows an example of the case in which all of the targets of display (that is, the aggregation scope) in the table  65  shown in  FIG. 12A  through  FIG. 14A  and the display copy pair state table  67  shown in  FIG. 11B  are copy groups. A mark  601  shows a PVOL group of one or a plurality of PVOLs or a SVOL group of one or a plurality of SVOLs, and each of lines  603 ,  605 ,  607 , and  609  represents a copy group. Specifically, the short lines  603  and  609  indicate a copy group of local copies, and the long lines  605  and  607  indicate a copy group of remote copies. More specifically, the short line  603  indicates a target of display (copy group) “CG-C”, the long line  605  indicates a target of display (copy group) “CG-A”, the long line  607  indicates a target of display (copy group) “CG-B”, and the short line  609  indicates a target of display (copy group) “CG-D”. The cascade forms of the copy group “CG-C” and the copy group “CG-A” can be detected by, for example, receiving, from the control program  75 , the ID of each logical volume configuring the copy pairs “Pair-A”, “Pair-B”, “Pair-D” and “Pair-E” and the ID of the storage subsystem  31  comprising the logical volume, and determining whether the logical volume ID and the storage subsystem ID are the same, and the detected configurations can be displayed as shown in  FIG. 14B  (the above screen configuration is applied for  FIG. 15A  and  FIG. 16A ). 
         [0167]    The storage monitoring program  63  displays, in the vicinity of each line, an icon representing the pair state corresponding to the target of display on the display copy pair state table  67 . Here, the pair state is “normal” for all the targets for display, thus an icon  611  indicating “normal” pair state is displayed. The user can immediately understand that all copy pairs are in an expected state regardless of the type of copy, by looking at the screen shown in  FIG. 14B . 
         [0168]    (2) When the pair state for display of at last one copy pair is “warning”. 
         [0169]      FIG. 15A  shows a display example of the monitor screen  61  in the case where there exists a copy pair in the copy groups, which is determined as “warning”, the copy groups being targets of monitoring.  FIG. 15A  is a screen displayed on the basis of the display copy pair state table  67  shown in  FIG. 11B . Specifically, the storage monitoring program  63  displays an icon  613  showing the pair state corresponding to “warning”, in the vicinity of the lines corresponding respectively to the target of displays “CG-C” and “CG-B”. Accordingly, the user can immediately understand the copy group having copy pairs which are not in the error state but may be brought into the involuntary state. 
         [0170]    Moreover, in response to that the icon  613  representing “warning” is designated by the user (that the cursor of the mouse is caused to overlap on the icon  613  or that the icon  613  is clicked when the cursor overlaps thereon), the storage monitoring program  63  can display the detailed information (detailed information recorded on the display copy pair state table  67 ) of the target of display corresponding to the icon  613 , on a pop-up. Specifically, the storage monitoring program  63  does not display the detailed information first, thereby creating a screen so as to have a nice panoramic view thereof, and then displays the detailed information in response to a request from the user. The pop-up may be deleted when a designation for deleting the pop-up is received from the user (for example, when the cursor is no longer allowed to overlap on the icon  613  or when the mouse is clicked). If there are a number of icons  613  representing “warning”, a plurality of pop-ups may be displayed on a single monitor screen  61 . In this case, the storage monitoring program  63  may display each of the pop-ups on a position which does not overlap with other pop-ups, or may display each pop-up by adjusting (reducing, for example) the size of the pop-up so as to avoid an overlap between the pop-ups. 
         [0171]    It should be noted in the screen shown in  FIG. 14B  that, since the target of display of the copy group “CG-D” is “POOL-A” in  FIG. 11B , the storage monitoring program  63  displays a mark  614 , which represents a pool volume, instead of displaying the copy group “CG-D”, and further displays an icon  615  representing “error” inside the mark  614  (or in the vicinity of the mark  614 ) since the pair state is “error”. 
         [0172]    (3) When the pair state for display of at least one copy pair is “error”. 
         [0173]    Regarding a copy group as the target of monitoring, a display example of the monitor screen  61  in the case where an error occurs at a communication port for performing remote copy is shown in  FIG. 15B , and a display example of the monitor screen  61  in the case where an error occurs at the storage subsystem  31  is shown in  FIG. 15C . According to  FIG. 15B  and  FIG. 15C , since the icons corresponding to the communication port and the storage subsystems indicate errors, the user can have a panoramic understanding of sections where error occur. This case is described in detail hereinafter. 
         [0174]    In the display copy pair state table  67 , in the case where the targets of display (aggregation scope) of the copy groups “CG-A” and “CG-B” are the communication ports and the pair state of target of display “CTL-A” is “normal” but the pair state of the target of display “CTL-B” is “error”, the storage monitoring program  63  displays the screen shown in  FIG. 15B . Specifically, since the aggregation scope is the communication ports, the storage monitoring program  63  displays, instead of the marks of the copy groups, a mark  621  representing a subsystem of “Array-A” and a mark  623  representing a subsystem of “Array-B”, displays a mark  625  representing the communication port “CTL-A” and a mark  627  representing the communication port “CTL-B”, displays lines showing that two subsystems are connected via the communication ports, and further displays an icon representing each pair state in the vicinity of each of the lines. At this moment, the line corresponding to a “normal” pair state is displayed by an arrow indicating that transfer is carried out, but the line corresponding to an “error” pair state is displayed simply as a line indicating that transfer is not carried out. By looking at the screen of  FIG. 15B , since an error occurs at a communication port of one of the subsystems, the user can immediately recognize that all copy pairs belonging to the communication port are in the error state. It should be noted that when the target of display is “port” and the pair state of the target of display is the error state, such panoramic display is performed even when other port of the same storage subsystem is normal and the target of display is not “port”. Therefore, the storage monitoring program  63  may change the target of display to “port”. Alternatively, if other port is normal, the copy pairs belonging to this port may be displayed in accordance with the aggregation scope of the copy pairs. 
         [0175]    In the display copy pair state table  67 , when the target of display (aggregation scope) for the copy groups “CG-A” and “CG-B” is the storage subsystem and the pair states of the targets of display “Array-A” and “Array-B” are “error”, the storage monitoring program  63  displays the screen shown in  FIG. 15C . Specifically, since the aggregation scope is the storage subsystem, the storage monitoring program  63  displays, instead of the marks of the copy groups, the mark  621  representing the subsystem of “Array-A” and the mark  623  representing the subsystem of “Array-B”, and further displays an icon corresponding to an “error” pair state inside or in the vicinity of each of the marks  621  and  623 . By looking at the screen of  FIG. 15C , since an error occurs at the both subsystems, the user can immediately recognize that all copy pairs belonging to each of the subsystems are in the error state. 
         [0176]    Although not shown in particular, as in  FIG. 15A , in  FIG. 15B  and  FIG. 15C  as well, the user can referred to the detailed information corresponding to the targets of display by designating the icons corresponding to the errors. Moreover, in the example of  FIG. 15C , although a failure occurs in both local and remote storage subsystems, if a failure occurs in either one of the storage subsystems the icon representing the error is displayed only on the corresponding storage subsystem 
         [0177]    (4) When the pair state for display of at least one copy pair is “backup/restoration being executed”. 
         [0178]      FIG. 16A  shows a display example of the monitor screen  61  in the case where there exist a copy pair in the copy groups as the targets of monitoring, which is determined as “normal”, and a copy pair determined as “backup/restoration being executed”. Specifically,  FIG. 16A  shows an example of the case where the pair state of the target of display (copy group) “CG-C” indicates “backup/restoration being executed”. The storage monitoring program  63  displays an icon  631 , which indicates a pair state changed by an intentional operation of the user, in the vicinity of the line corresponding to the target of display “CG-C”. According to  FIG. 16A , the user can immediately recognize that a “normal” pair state of a copy group is the pair state changed by the intentional operation of the user. Whether such an operation is the backup/restore operation or the maintenance operation can be identified as change performed by the backup/restore operation, since the target of display indicates the copy group. 
         [0179]    (5) When the maintenance work is being executed. 
         [0180]      FIG. 16B  shows a display example of the monitor screen  61  in the case where an operation mode of the storage subsystem (for example, the subsystems “Array-A” and “Array-B”) having the copy groups, which are the targets of monitoring, is “under maintenance”. In this case, in the display copy pair state table  67 , the IDs of the storage subsystems are written as the targets of display and “maintenance” is written as the pair states, thus the storage monitoring program  63  displays marks indicating the subsystems, and further displays, inside (or in the vicinity) of the marks, the icons  631  indicating that the pair state is a pair state changed by an intentional operation of the user, in accordance with the table  67 . According to  FIG. 16B , unlike  FIG. 16A , the marks are displayed in units of the subsystem and the icons  631  are displayed inside the marks of the subsystems, whereby the user can immediately recognize that all copy pairs belonging to each of the subsystems are affected by the maintenance work. It should be noted in the example shown in  FIG. 16B  that, although the operation modes of the both local and remote storage subsystems  31  indicate “under maintenance”, if only one of the storage subsystems  31  is under maintenance the icon of “under maintenance” is displayed only on the corresponding storage subsystem. 
         [0181]    Although the above has described the embodiments of the present invention, the above descriptions are merely examples provided to describe the present invention and thus are not to restrict the scope of the present invention to these embodiments. The present invention can be implemented in various other embodiments. 
         [0182]    For example, on the screen for displaying in units of the copy group or in units of the common storage resource, display may be performed so that a volume group configuring each copy group or subsystems having the common storage region can be specified easily. For example, a display region representing each subsystem may be prepared, and a mark representing the volume groups owned by the subsystem or a mark representing the common storage resource may be displayed inside the display region. 
         [0183]    Moreover, for example, the storage monitoring program  63  may acquire information indicating a detailed copy type from the task server  11  or the storage subsystem  31 , an display a mark representing the pair state and its detailed copy type. “Detailed copy type” is not merely a broad type such as a local copy or a remote copy, and thus may be displayed with a mark indicating, even in the case of the local copy, that a snapshot is acquired using a pool volume or an actual volume, or indicating, even in the case of the remote copy, whether a copy type is asynchronous remote copy using a side file, asynchronous remote copy using JNLVOL, or synchronous remote copy. 
         [0184]    Furthermore, when the data related to three or more storage subsystems are registered in the table  65  shown in  FIG. 12A  through  FIG. 14A  and in the display copy pair state table  67  shown in  FIG. 11B , display can be performed as shown in  FIG. 18A  through  FIG. 18D . Specifically, for example, the monitoring server  51  can specify configurations of the three or more storage subsystems from the copy pair state table  65 , and, on the basis of the specified configurations and the display copy pair state table  67 , create and display at least one display screen of the display screens shown in  FIG. 18A  through  FIG. 18D .