Abstract:
Storage system arrangements having status information including both copy group summary status information providing a status of a group of the plurality of copy pairs, and detailed status information detailing a status of a copy pair included in the group; and wherein said status management unit monitors the status information of said plurality of copy pairs, wherein the management computer acquires, from the storage apparatus, the copy group summary status information as summary information for a group of the plurality of copy pairs having a failure status for the group, and displays said summary information on said display, if the summary information indicates a normal status, the management computer displays the summary information only; and if the summary information indicates a failure status, the management computer displays, upon receiving selection of said summary information, detailed status information of a copy pair that belongs to the group.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a continuation of U.S. application Ser. No. 12/034,977, filed Feb. 21, 2008. This application relates to and claims priority from Japanese Patent Application No. 2007-286652, filed on Nov. 2, 2007. The entirety of the contents and subject matter of all of the above is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention generally relates to a storage system configured from a host computer, a storage apparatus and a management computer, and to a storage subsystem storing information associated with access from the storage system and 
     the host computer, and in particular to technology for acquiring the status of copy pairs configured with the storage apparatus. 
     The importance of nondisruptive operation and data protection in corporate information systems is ever-increasing due to the globalization of markets and the provision of 24/7 services via the Web. Nevertheless, there are numerous risks such as terrorism and natural disasters that may lead to the disruption or data loss of corporate information systems. In order to reduce these risks, it is necessary to assume that such disasters or failures will occur, and to plan in advance by when and how to restore the system that is shut down during the disaster or failure. This is known as “Disaster Recovery,” and will be hereinafter referred to as “DR.” 
     With DR, it is important to preliminarily set forth indexes indicating which data at what point in time is to be recovered by when, and operate the system while monitoring that such indexes are being observed. Among the foregoing indexes, the former; namely, the index showing which data at what point in time should be recovered is referred to as a “Recovery Point Objective” (hereinafter referred to as “RPO”), and the latter; namely, the index showing by when the business should be resumed after being affected by the disaster is referred to as a “Recovery Time Objective.” 
     Generally, a case where a volume to be copied is stored in the same storage apparatus as the foregoing volume is referred to as a local copy, and a case where a volume to be copied is stored in a different storage apparatus than the foregoing volume is referred to as a remote copy, and this is employed in information systems demanded of high reliability. Local copy and remote copy are sometimes collectively referred to as replication. According to this replication technology, even when a failure occurs in one of the volumes and becomes inoperable, the system operation can be continued by using the data stored in the other volume. 
     The two volumes of a copy source and a copy destination of a replication relationship are referred to as a copy pair. Normally, a copy pair is grouped in host computer units or application units, and the copy pair is controlled and monitored in such units. A plurality of copy pairs grouped in host computer units or application units are referred to as a copy group. 
     Remote copy is fundamental technology for realizing DR which prepares a remote site at a location that is geographically distant from the site (local site) conducting the business, and creates the entirely same data as the local site in the remote site. 
     There are two types of remote copy; namely, synchronous remote copy which returns a write completion reply to the server upon waiting for the data write completion reply on the remote site side when the business host issues an I/O [request], and asynchronous remote copy which returns a write completion reply to the server without waiting for the data write completion reply on the remote site side. With asynchronous remote copy, since it is possible to suppress the influence on the business reply performance even during the bandwidth fluctuation of the network or sudden fluctuations in the business load, this is effective when installing the remote site at a great distance or when using a network line with unstable performance. 
     Japanese Patent Laid-Open Publication No. 2007-47892 discloses technology concerning a storage system comprising a plurality of host computers and a plurality of storage apparatuses, wherein one storage apparatus controls the copy group extending across a plurality of storage apparatuses, and acquires the copy group and the copy pair status configuring such copy group. 
     SUMMARY 
     Incidentally, the size of storage systems is increasing exponentially pursuant to the advancement of the information society and the like. In connection with this, the scope of replication that must be monitored is also ever-increasing explosively. For instance, the number of copy pairs configuring a copy group to be used by a single application is on the verge of reaching several ten to hundred thousand copy pairs. 
     Meanwhile, asynchronous remote copy is characterized in that, when a failure occurs to even one copy pair configuring a copy group, all copy pairs configuring that copy group will be affected. 
     With asynchronous remote copy, it is necessary to maintain the consistency of the writing order in copy group units. Thus, if a pair link is disconnected as a result of a failure occurring in any one of the copy pairs configuring the copy group, the storage performs the operation of deleting the pair link of all copy pairs configuring the copy group. The RPO will increase if a failure occurs and the pair link is left in a disconnected state. Thus, in order to maintain the RPO, it is necessary to detect and correct a failure as soon as possible. 
     The present invention was made in view of the foregoing circumstances. Thus, an object of the present invention is to provide a storage system and a storage subsystem capable of inhibiting the increase of RPO by effectively monitoring the status of copy pairs configured by a storage apparatus and instantaneously detecting a failure that may cause the increase of RPO in a large-scale storage system. 
     In order to achieve the foregoing object, the present invention consolidates the status information of a plurality of [copy] pairs in a copy group obtained by grouping a plurality of copy pairs in a storage system, and changes the provision granularity of status information to the information request source computer according to the copy group status. 
     Specifically, proposed is a storage system in which a storage apparatus is provided with a primary storage unit for storing write data from the host computer as a primary volume, a secondary storage unit for storing copied data of write data stored in the primary storage unit as a secondary volume, and a status management unit for collecting and managing status information of a plurality of copy pairs from the primary storage unit and the secondary storage unit with a copy source primary volume and a copy destination secondary volume as a single copy pair. The status management unit monitors the status information of the plurality of copy pairs and transfers the status information of the copy pair subject to a failure to the management computer during a failure, and transfers only the flag information showing information of the overall copy pair to the management computer during a normal status. 
     As a result of adopting the foregoing configuration, it is possible to facilitate the cause unfolding by the administrator and thereby inhibit the increase of RPO during a failure. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a system configuration diagram showing a first embodiment of a storage system according to the present invention; 
         FIG. 2  is a diagram showing the transition of the copy pair status in the first embodiment; 
         FIG. 3  is a configuration diagram showing an example of a copy group status determination table in the first embodiment; 
         FIG. 4  is a configuration diagram showing an example of a pair status table in the first embodiment; 
         FIG. 5  is a configuration diagram showing an example of a summary table in the first embodiment; 
         FIG. 6  is a conceptual diagram showing an example of an additional information table in the first embodiment; 
         FIG. 7  is a flowchart showing the processing operation of a storage microprogram to perform update processing of a management table in the first embodiment; 
         FIG. 8  is a configuration diagram showing an example of a transfer table determination table in the first embodiment; 
         FIG. 9  is a flowchart showing the processing operation of a storage microprogram to perform the transfer of status information of a copy pair in the first embodiment; 
         FIG. 10  is a configuration diagram showing an example of a copy group summary table in the first embodiment; 
         FIG. 11  is a configuration diagram showing an example of a copy group pair table in the first embodiment; 
         FIG. 12  is a flowchart showing the processing operation of a management program to perform copy group status acquisition processing in the first embodiment; 
         FIG. 13A  is a diagram showing a display example of a summary GUI in the first embodiment; 
         FIG. 13B  is a diagram showing another display example of a summary GUI in the first embodiment; 
         FIG. 13C  is a diagram showing yet another display example of a summary GUI in the first embodiment; 
         FIG. 14A  is a diagram showing a display example of a detailed GUI in the first embodiment; 
         FIG. 14B  is a diagram showing another display example of a detailed GUI in the first embodiment; 
         FIG. 15  is a diagram showing a display example of a summary GUI in the first embodiment; 
         FIG. 16  is a system configuration diagram showing a second embodiment of a storage system according to the present invention; 
         FIG. 17  is a configuration diagram showing an example of an additional information table in the second embodiment; 
         FIG. 18  is a configuration diagram showing an example of a copy group summary table in the second embodiment; 
         FIG. 19  is a diagram showing a display example of a summary GUI in the second embodiment; 
         FIG. 20  is a configuration diagram showing an example of a copy group definition command table in the second embodiment; 
         FIG. 21  is a system configuration diagram showing a third embodiment of a storage system according to the present invention; and 
         FIG. 22  is a flowchart showing the processing operation of a management program and a storage microprogram to perform update processing of a management table in the third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     First Embodiment 
     The first embodiment of the present invention is now explained. Incidentally, the present invention shall not be limited to the following embodiments explained below. 
       FIG. 1  is a block diagram showing the configuration of a storage system according to the present embodiment. In this system, with the type of replication being a local copy to be performed in a single storage apparatus  1500 , the storage apparatus  1500  and a host computer  1300  are mutually connected via a data network  1100 . Although this embodiment explains a case where the data network  1100  is a storage area network, it may also be an IP (Internet Protocol) network or another data communication network. 
     The storage apparatus  1500  and a management computer  1400  are connected via a management network  1200 . Although this embodiment explains a case where the management network  1200  is an IP network, it may also be a storage area network or another data communication network. In addition, the data network  1100  and the management network  1200  may be the same network, and the management computer  1400  and the host computer  1300  may be the same computer. 
     For the sake of explanation, although  FIG. 1  shows a case where there is one storage apparatus  1500 , one host computer  1300  and one management computer  1400 , and the present invention is not limited to the foregoing configuration. 
     The storage apparatus  1500  is configured as a storage subsystem comprising a disk device  1510  for storing data, and a disk controller  1520  for controlling the storage apparatus [ 1520 ]. The disk device  1510  is configured from a plurality of volumes  1511 ,  1512 ,  1513 . The volumes  1511 ,  1512 ,  1513  may be physical volumes such as hard disk drives (HDDs), or logical volumes such as logical devices, and there is no particular limitation in the present invention. The volumes are able to configure a copy pair, and the operations to be performed to the copy pair and the status transition based on such operations will be described later. 
     Here, the disk device  1510  functions as a primary storage unit for storing write data from the host computer  1300  as a primary volume, and a secondary storage unit for storing the copied data of such write data stored in the primary storage unit as a secondary volume, and the disk controller  1520  functions as a status management unit for collecting and managing the status information of a plurality of copy pairs from the primary storage unit and the secondary storage unit with a copy source primary volume and a copy destination secondary volume as a single copy pair. 
     In the foregoing case, the disk controller  1520  monitors the status information of the plurality of copy pairs according to the status of failure, and, upon transferring information, transfers detailed information concerning a copy pair as status information of the copy pair subject to the failure to the management computer  1400  as an information request source, and transfers flag information showing the overall status of all other copy pairs as the status information of the other copy pairs to the management computer  1400 . 
     For the sake of explanation, although  FIG. 1  shows a case where there are three volumes, the present invention is not limited to the foregoing configuration. 
     The disk controller  1520  is provided with a host I/F  1528 , a management I/F  1526 , a disk I/F  1525 , a memory  1521 , a CPU  1523 , and a local disk  1527 . The local disk  1527  is a disk device such as a hard disk connected to the disk controller  1520 , and stores a storage microprogram  1530 . The storage microprogram  1530  is loaded in the memory  1521  of the disk controller  1520 , and executed by the CPU  1523 . 
     Although this embodiment explains a case where the storage microprogram  1530  is stored in the local disk  1527  of the disk controller  1520 , the present invention is not limited to the foregoing configuration. For example, these programs and tables may also be stored in a flash memory provided to the disk controller, or in an arbitrary disk in the disk device  1510 . 
     The storage microprogram  1530  receives a command from the management computer  1400  and/or host computer  1300  and controls the copy pair or acquires the copy pair status. As the control of copy pairs, there is the creation of a copy pair for newly creating copy pair, resynchronization of a copy pair for matching the contents of a secondary volume with the contents of a primary volume, and suspending of a copy pair for discontinuing the synchronous relationship. Acquisition of a copy pair status refers to the acquisition of information concerning which status the respective copy pairs are in based on the foregoing control. Transition of the copy pairs to the various statuses based on a control command will be described later. The management table  1522  stored in the memory  1521  will also be described later. 
     The host I/F  1528  is an interface to the data network  1100 , and sends and receives data and control commands to and from the host computer  1300 . The management I/F  1526  is an interface to the management network  1200 , and sends and receives data and control commands to and from the management computer  1400 . The disk I/F  1525  is an interface to the disk device  1510 , and sends and receives data and control commands. 
     The host computer  1300  is configured from an input device  1340  such as a keyboard or a mouse, a CPU  1320 , a display device  1350  such as a CRT, a memory  1330 , a storage I/F  1360 , and a local disk  1310 . 
     The storage I/F  1360  is an interface to the data network  1100 , and sends and receives data and control commands to and from the storage apparatus  1500 . The local disk  1310  is a disk device such as a hard disk connected to the host computer  1300 , and stores an application  1312 . 
     The application  1312  is loaded in the memory  1330  of the host computer  1300 , and executed by the CPU  1320 . The application  1312  is an application for reading and writing data from and into the volumes in the storage apparatus  1500 , and, for instance, is a DBMS or a file system. 
     For the sake of explanation, although  FIG. 1  shows a case where there is one application  1312 , the present invention is not limited to the foregoing configuration. 
     The management computer  1400  is configured from an input device  1430  such as a keyboard or a mouse, a CPU  1440 , a display device  1450  such as a CRT, a memory  1420 , a local disk  1410 , and a management I/F  1460  for sending and receiving data and control commands to and from the storage apparatus  1500  for system management. 
     The local disk  1410  is a disk device such as a hard disk connected to the management computer  1400 , and stores a management program  1412 . The management program  1412  is loaded in the memory  1420  of the management computer  1400 , and executed by the CPU  1440 . 
     The management program  1412  is a program for providing the function of operating and monitoring the copy pairs of one or more storage apparatuses via the input device  1430  such as a keyboard or a mouse or via the display device  1450  such as a graphical user interface (GUI). The management I/F  1460  is an interface to the management network  1200 , and sends and receives data and control commands to and from the storage  1500 . The management table  1422  in the memory  1420  will be described later. 
       FIG. 2  shows the transition of the copy pair status. The statuses shown in  FIG. 2 , as indicated in the explanatory note  2900 , can be broadly classified into a stationary status  2910 , a transient status  2920 , and a failure status  2930 . Pair  2100 , Simplex  2200 , and Suspend  2300  are collectively referred to as a stationary status  2910 . 
     Copying  2110  and  2120 , Suspending  2130 , and Deleting  2210  are collectively referred to as a transient status  2920 . The difference between Copying  2110  and  2120  will be explained later. Error  2800  is referred to as a failure status  2930 . 
     The status transition from the stationary status  2910  to the transient status  2920  arises based on a command from the user. A command from a user is usually issued via the input device  1340  of the host computer  1300 , and received and executed by the storage microprogram  1530  loaded in the memory  1521  of the storage apparatus  1500 . 
     Nevertheless, the command from a user may also be issued via the input device  1430  of the management computer  1400 . The status transition from the transient status  2920  to the stationary status  2910  is conducted by the storage microprogram  1530  loaded in the memory  1521  of the storage apparatus  1500  without the intervention of the user&#39;s command. 
     Simplex  2200  is a status where a copy pair is not formed. When the copy pair status is Simplex  2200 , the copy pair status changes to Copying  2110 , which is one of the transient statuses  2920 , as a result of a copy pair creation command  2115  being issued by the user. Copying  2110  is a copy pair status showing that data is being copied from a primary volume to a secondary volume in order to make the corresponding copy pair into a synchronous status. 
     When the synchronization of the copy pair is complete, the copy pair status is changed from Copying  2110  to Pair  2100  without the intervention of the user&#39;s command. Pair  2100  is a copy pair status showing that the primary volume and the secondary volume are in synch. 
     As a result of a copy pair deletion command  2218  being issued from the user when the copy pair status is Pair  2100 , the copy pair status changes to Deleting  2210 , which is one of the transient statuses  2920 . Deleting  2210  is a copy pair status showing that the corresponding copy pair is deleting its copy pair relationship. When the deletion of the copy pair relationship is complete, the copy pair status changes from Deleting  2210  to Simplex  2200  without the intervention of the user&#39;s command. 
     As a result of a copy pair suspend command  2135  being issued from the user when the copy pair status is Pair  2100 , the copy pair status changes to Suspending  2130 , which is one of the transient statuses  2920 . Suspending  2130  is a copy pair status showing that the corresponding copy pair is suspending the copy pair relationship. 
     When the suspending of the copy pair relationship is complete, the copy pair status changes from Suspending  2130  to Suspend  2300  without the intervention of the user&#39;s command. Suspend  2300  is a copy pair status showing that, although the copy pair relationship is being maintained internally, the synchronization of the primary volume and the secondary volume is being discontinued. 
     As a result of a copy pair resynch command  2125  being issued from the user when the copy pair status is Suspend  2300 , the copy pair status changes to Copying  2120 , which is one of the transient statuses  2920 . Copying  2110  and Copying  2120  are the same in that data is copied from the primary volume to the secondary volume in order to make the copy pair a synchronous status. The difference is in that Copying  2110  copies all data of the primary volume to the secondary volume, while Copying  2120  only copies data that was written into the primary volume after the suspend command  2135  was issued to the secondary volume. When the synchronization of the copy pair is complete, the copy pair status changes from Copying  2120  to Pair  2100  without the intervention of the user&#39;s command. 
     As a result of a copy pair deletion command  2215  being issued from the user when the copy pair status is Suspend  2300 , the copy pair status changes to Deleting  2210 , which is one of the transient statuses  2920 . When the deletion of the copy pair relationship is complete, the copy pair status changes from Deleting  2210  to Simplex  2200  without the intervention of the user&#39;s command. 
     When some kind of failure occurs in Pair  2100 , Simplex  2200 , and Suspend  2300  as all stationary statuses  2910  and in Copying  2110  and  2120 , Suspending  2130 , and Deleting  2210  as all transient statuses  2920 , the copy pair status changes to Error  2800 . 
       FIG. 3  shows the configuration of a copy group status determination table  3000  tabularizing the relationship of the status of the individual copy pairs configuring the copy groups, and the status of the copy groups. Although this embodiment explains a case where the copy group status determination table  3000  is retained in the storage microprogram  1530 , the present invention can also be implemented even if the copy group status determination table  3000  is stored separately from the storage microprogram  1530 ; for instance, stored in the local disk  1527  of the storage apparatus or in a disk of the disk device  1510 . 
     As described above, a copy pair is usually grouped in host computer units or application units, and a copy pair is controlled or monitor in such units. A plurality of copy pairs grouped in host computer units or application units is referred to as a copy group. 
     The copy group status determination table  3000  is configured from a copy pair status field  3100 , a copy group status field  3200 , and a flag field  3300 . 
     The copy pair status field  3100  is a field displaying the status of the individual copy pairs configuring a copy group. For example, the field  3105  displays that the status of all copy pairs configuring a copy group is Simplex  2200 . The copy group status field  3200  is a field displaying the copy group status when the status of the respective copy pairs configuring the corresponding copy group is as shown in the copy pair status field  3100 . 
     The flag field  3300  is a field displaying whether the copy group is of a stationary status, a transient status or a failure status. Whether the copy group is a stationary status, a transient status or a failure status depends on the copy pair status. 
       FIG. 4 ,  FIG. 5 , and  FIG. 6  are configuration diagrams of a pair status table  4000 , a summary table  5000 , and an additional information table  6000  configuring the management table  1522  created in the memory  1521  of the storage apparatus  1500 . The respective tables are explained in detail below. 
       FIG. 4  shows the configuration of the pair status table  4000  displaying information of the copy pairs configuring a copy group. The pair status table  4000  is configured from a copy group name field  4100 , a copy pair name field  4200 , a copy pair status field  4300 , a primary volume name field  4400 , and a secondary volume name field  4500 . 
     The copy group name field  4100  stores the name of the copy group. The copy pair name field  4200  stores the name of the copy pair. Although a copy pair is uniquely identified based on the primary volume name and the secondary volume name, since this alone will make management of a copy pair difficult, a copy pair is usually managed with a logical name as the copy pair name described above. 
     The copy pair status field  4300  stores the status of the copy pair. This field  4300  stores one status among Pair  2100 , Simplex  2200 , Suspend  2300 , Copying  2110  and  2120 , Suspending  2130 , Deleting  2210 , and Error  2800  shown in  FIG. 2 . 
     The primary volume name field  4400  stores the volume name of the primary volume of the copy pair. The secondary volume name field  4500  stores the volume name of the secondary volume of the copy pair. 
     According to the pair status table  4000  in this embodiment, the copy group CG. 01  is configured from three copy pairs; namely, a copy pair  4600  named P 1 , a copy pair  4700  named P 2 , and a copy pair  4800  named P 3 , and the status of all of these copy pairs is Pair. 
     A copy group is normally defined by grouping a plurality of copy pairs in host computer  1300  units or application units at the start of operation. A copy group is defined by the copy group name, the copy pair name of the copy pairs configuring the copy group, a primary volume name, and a secondary volume. 
     When the copy group is defined, the storage apparatus  1500  creates a pair status table  4000  in the management table stored in the memory  1521 , and, based on the defined information, rewrites the copy group name field  4100 , the copy pair name field  4200 , the primary volume name field  4400 , and the secondary volume name field  4500 . Here, the pair status field  4300  is a blank column. 
       FIG. 5  shows the configuration of a summary table  5000  displaying the copy group status as summary information. The summary table  5000  is configured from a copy group name field  5100 , a copy group status field  5200 , and a flag field  5300 . 
     The copy group name field  5100  displays the name of the copy group. The copy group status field  5200  displays the status of the copy group. The copy group status can be uniquely determined by referring to the copy group status determination table  3000  shown in  FIG. 3  if the status of the individual copy pairs configuring the copy group is known, and the value thereof is one among Simplex, Copying, Pair, Suspending, Suspend, Deleting, and Error. 
     The flag field  5300  is a field displaying whether the copy group is a stationary status, a transient status or a failure status. The value to be stored in the flag field  5300  can be uniquely determined by referring to the copy group status determination table  3000  shown in  FIG. 3  if the status of the individual copy pairs configuring the copy group is known, and the value thereof is one among a stationary status, a transient status, and a failure status. 
       FIG. 6  shows the configuration of an additional information table  6000  storing additional information of the copy group. The additional information table  6000  is configured from a copy group name field  6100  and a concordance rate field  6200 . 
     The copy group name field  6100  displays the name of the copy group. The concordance rate field  6200  displays the concordance rate of the corresponding copy group. A concordance rate is an index showing the degree of synchronization between the primary volume and the secondary volume when the copy group status is Pair. 
     In this embodiment, the concordance rate of a copy group  6300  named CG. 01  is shown to be 98%. The concordance rate is not referred to unless the status of the corresponding copy group is Pair. 
     The update processing of the management table  1522  created in the memory  1521  of the storage apparatus  1500  is now explained with reference to the flowchart  7000  of  FIG. 7 . This update processing is performed by the storage microprogram  1530  loaded in the memory  1521  of the storage apparatus  1500 . 
     Foremost, the storage microprogram  1530  receives a management table update command (step  7100 ). This command may be periodically performed by the microprogram  1530  by providing a timer to the storage microprogram  1530 , performed periodically provided by the management computer  1400  using the foregoing timer, or performed randomly according to instructions from the user. 
     Subsequently, the storage microprogram  1530  acquires all copy pair statuses configuring a copy group (step  7200 ), and updates the pair status table  4000  based on the copy pair status acquired at step  7200  (step  7300 ). Here, when the storage microprogram  1530  is to repeat the acquisition of the pair status without changing the configuration concerning a certain copy group, it updates only the copy pair status field  4300  in the pair status table  4000 . 
     The storage microprogram  1530  thereafter updates the copy group status field  5200  and the flag field  5300  of the summary table  5000  based on the copy group status determination table  3000  (step  7400 ), refers to the copy group status field  5200  of the updated summary table  5000 , and checks whether the copy group status is Pair or of another status (step  7500 ). 
     If the copy group status is Pair at step  7500 , the storage microprogram  1530  acquires the concordance rate of the copy group and stores it in the concordance rate field  6200  of the additional information table  6000  (step  7600 ), stores the concordance rate of the copy group in the concordance rate field  6200  of the additional information table  6000 , and then ends the processing (step  7700 ). 
     Meanwhile, if the copy group status is not Pair at step  7500 , the storage microprogram  1530  directly ends the processing (step  7700 ). 
       FIG. 8  shows the configuration of the transfer table determination table  8000  retained in the storage microprogram  1530  for determining the table to be transferred to the management computer  1400 . Although this embodiment explains a case where the transfer table determination table  8000  is retained in the storage microprogram  1530 , the present invention can also be implemented even if the transfer table determination table  8000  is stored separately from the storage microprogram  1530 ; for instance, stored in the local disk  1527  of the storage apparatus or in a disk of the disk device  1510 . 
     The transfer table determination table  8000  is configured from a flag value field  8100  and a transfer table type field  8200 . The transfer table type field  8200  is configured from a summary table field  8220 , a pair status table field  8240 , and an additional information field  8260 . 
     The flag value field  8100  is one among stationary, failure or transient. The transfer table type field  8200  is configured from a summary table field  8220 , a pair status table field  8240 , and an additional information table field  8260 , and shows the table to be transferred according to the flag value. 
     The field indicating “√” shows the table to be transferred, and the field indicating “−” shows the table that does not need to be transferred. For example, if the flag value is the stationary status  8320 , the summary table  5000  and the additional information table  6000  are subject to transfer. 
     The operation upon receiving a copy pair status transfer command to be executed by the storage microprogram  1530  is now explained according to the flowchart  9000  of  FIG. 9 . 
     Foremost, the storage microprogram  1530  receives a copy pair status transfer command (step  9100 ). This command is usually issued by the management program  1412  of the management computer  1400 . 
     Subsequently, the storage microprogram  1530  refers to the flag value stored in the flag field  5300  of the summary table  5000 , further refers to the transfer table determination table  8000 , and determines the table among the three tables to be transferred according to the corresponding flag value (step  9200 ). 
     The storage microprogram  1530  thereafter transfers the table determined to be transferred at step  9200  to the request source in the memory  1521  (step  9300 ), and, when the transfer is complete, ends the processing (step  9400 ). 
       FIG. 10  and  FIG. 11  show the configuration of a copy group summary table  10000  and a copy group pair table  11000  configuring the management table  1422  created in the memory  1420  of the management computer  1400 . The respective tables are explained in detail below. 
       FIG. 10  shows the configuration of the copy group summary table  10000  storing summary information of copy groups. The copy group summary table  10000  is configured from a copy group name field  10100 , a copy group status field  10200 , a flag field  10300 , and a concordance rate field  10400 . 
     The copy group name field  10100  displays the name of the copy group. The copy group status field  10200  displays the status of the copy group. The copy group status is one among Simplex, Copying, Pair, Suspending, Suspend, Deleting, and Error. 
     The flag field  10300  is a field displaying whether the copy group is of a stationary status, a transient status, or a failure status. The value stored in the flag field  5300  is one among stationary status, transient status, and failure status. The concordance rate field  10400  displays the concordance rate of the corresponding copy group. The concordance rate is referred to only when the status of the corresponding copy group is Pair. 
       FIG. 11  shows a configuration of the copy group table  11000  storing the status of the individual copy pairs configuring a copy group. The configuration of the copy group table  11000  is the same as the pair status table  4000  displaying information of the copy pairs configuring the copy group shown in  FIG. 4 . 
     The copy group status acquisition processing to be executed by the management program  1412  loaded in the memory  1420  of the management computer  1400  is now explained with reference to the flowchart  12000  of  FIG. 12 . 
     Foremost, the management program  1412  receives a copy group status acquisition command (step  12100 ). This command may be performed by the management program  1412  as a result of providing a timer to the management program  1412 , or performed randomly according to the user&#39;s instructions. 
     Subsequently, the management program  1412  secures an area of maximum capacity obtainable from the storage apparatus as the management table  1422  in the memory  1422  of the management computer  1400  (step  12200 ). This area is determined by the size of the copy group summary table  10000 , and the size of the copy group pair table  11000  in which the size of the area is determined based on the number of copy pairs configuring a copy group. 
     The management program  1412  thereafter issues a copy pair status transfer command to the storage apparatus  1500  (step  12300 ). Here, the storage apparatus  1500  that received the copy pair status transfer command transfers the appropriate table to the management computer  1400  according to the flowchart shown in  FIG. 9 . In the foregoing case, one or more management tables are transferred from the storage apparatus  1500  to the management computer  1400 . These tables contain at least one summary table  5000 . 
     Thus, the management program  1412  rewrites the copy group status field  10200  and the flag field  10300  of the copy group summary table  10000  with the contents of the received summary table  5000  (step  12400 ). 
     Subsequently, the management program  1412  checks whether the copy group status  5200  of the received summary table  5000  is Pair (step  12500 ). If the copy group status  5200  of the received summary table  5000  is Pair at step  12500 , the management program  1412  rewrites the concordance rate field  10400  of the copy group summary table  10000  with the contents of the received additional information table  6000  (step  12600 ). 
     Meanwhile, if the copy group status  5200  of the received summary table  5000  is not Pair at step  12500 , the management program  1412  checks whether the flag value of the received summary table  5000  is failure (step  12700 ). 
     If the flag value is failure at step  12700 , the management program  1412  rewrites the pair status field  4300  of the copy group pair table  11000  with the contents of the received pair status table  4000  (step  12800 ), and then ends the processing (step  12900 ). If the flag value is a value other than failure at step  12700 , the management program  1412  directly ends the processing (step  12900 ). 
       FIG. 13A ,  FIG. 13B  and  FIG. 13C  shows examples of the summary GUI  13000  to be displayed on the display device  1450  of the management computer  1400 . The summary GUI  13000  is configured from a copy group name field  13100 , a copy group status field  13200 , and a concordance rate field  13300 . 
     This GUI is created based on information of the copy group summary table  10000  created in the memory  1420  of the management computer  1400 . The copy group name field  13100  displays the name of the copy group. The copy group status  13200  displays the status of the copy group. The copy group status is one among Simplex, Copying, Pair, Suspending, Suspend, Deleting, and Error. The concordance rate field  13300  displays the concordance rate of the corresponding copy group. The concordance rate is indicated as N/A if the corresponding copy group status is other than Pair since a valid value is not entered. 
       FIG. 13A  shows the screen display example  13400  in a case when the copy group status is Pair. Since the copy group status is Pair, the pair concordance rate is displayed in the concordance rate field  13300 . The pair concordance rate is an index showing the level of synchronization between the primary volume and the secondary volume as described above. 
     If the pair concordance rate deteriorates, it is possible to predict that some kind of failure may occur. Thus, as a result of the pair concordance rate being displayed when the copy group status is Pair, even when it is the same Pair status, it is possible to know whether the status is free of any problem, or entails the possibility of leading to a failure. 
       FIG. 13B  shows the screen display example  13500  in a case when the copy group status is Error. Since the copy group status is Error, N/A is indicated in the concordance rate field  13300 . The copy group name displayed in the copy group name field  13100  can be clicked. 
     In order to pursue which copy pair is causing the failure among the copy pairs configuring the copy group, a screen displaying a list of copy pairs can be called from this screen. The called screen will be described later. 
       FIG. 13C  shows the screen display example  13600  in a case when the copy group status is Copying. Since the copy group status is Copying, N/A is displayed in the concordance rate field  13300 . 
       FIG. 14A  shows an example of the detailed GUI example  14000  to be displayed as a result of clicking the copy group name displayed on the copy group name field  13100  of the summary GUI  13000  when the copy group status is Error. The detailed GUI example  14000  is configured from a copy pair name field  14100 , a copy pair status field  14200 , a primary volume field  14300 , and a secondary volume field  14400 . 
     This GUI is created based on information of the copy group pair table  11000  created in the memory  1420  of the management computer  1400 . The copy pair name field  14100  displays the name of the copy pair. Although a copy pair is uniquely identified based on the primary storage apparatus and its volume number and the secondary storage apparatus and its volume number, since this alone will make management of a copy pair difficult, a copy pair is usually managed with a logical name as the copy pair name described above. 
     The copy pair status field  14200  displays the status of the copy pair. This field displays one status among Pair  2100 , Simplex  2200 , Suspend  2300 , Copying  2110  and  2120 , Suspending  2130 , Deleting  2210 , and Error  2800  shown in  FIG. 2 . 
     The primary volume  14300  displays the volume name of the primary volume of the copy pair. The secondary volume  14400  displays the volume name of the secondary volume of the copy pair. 
     According to the detailed GUI example  14000  in this embodiment, the copy group CG. 01  is configured from three copy pairs; namely, a copy pair  14500  named P 1 , a copy pair  14600  named P 2 , and a copy pair  14700  named P 3 , and, since the copy pairs P 1  and P 3  are Pair, and [copy pair] P 2  is Error, it is evident that the copy pair P 2  is the cause of failure in the copy group CG. 01 . 
       FIG. 14B  shows an example of the detailed GUI example  14001  to be displayed as a result of the copy group name displayed on the copy group name field  13100  of the summary GUI  13000  when the copy group status is Error. The configuration of the table is the same as the table shown in  FIG. 14A . The detailed GUI example  14001  only displays a pair in which the [copy] pair status is Error. 
     In a large-scale configuration, there are cases where a single copy group is configured from vast quantities of copy pairs of several ten thousand or more. Even in the foregoing case, the copy group status will be Error when just a couple of copy pairs are subject to a failure. When a failure occurs, as a result of displaying only the copy pair that is causing the failure, it is possible to promptly know the cause of failure even in the foregoing large-scale configuration. 
     As described above, data is not transferred from the primary volume to the secondary volume when a failure occurs. Thus, when a disaster occurs that will lead to the loss of data of the primary volume during the occurrence of a failure, data during this time will be lost. Since this implies the increase of RPO, it is important to promptly know the cause of failure and to provide a function for dealing with such failure. 
     This embodiment explained a case where, if the copy group status is Error, the detailed GUI example  14000  or the detailed GUI example  14001  is displayed as a result of clicking the copy group name displayed on the copy group name field  13100  of the summary GUI  13000 . Nevertheless, the detailed GUI example  14000  and the detailed GUI example  14001  may both be displayed by switching the screens with a tab or the like. 
     In this embodiment, when a copy pair status transfer command is issued from the management computer  1400  to the storage apparatus  1500  and the copy group status is a stationary status or a transient status, only the summary table  5000  and the additional information table  5000  in the management table  1522  managed in the storage apparatus  1500  in which the table size is independent of the number of copy pairs are transferred to the management computer  1400 , and the pair status table  4000  in which the size expands according to the number of copy pairs is not transferred. 
     Thus, according to this embodiment, when the copy group status is a stationary status or a transient status, the greater the number of copy pairs configuring a copy group, the reduction effect of the data transfer volume between the management computer  1400  and the storage apparatus  1500  will increase in comparison to conventional methods of transferring the status of all copy pairs configuring a copy group. 
     In addition, according to this embodiment, when the copy group status is a stationary status or a transient status, the copy group status can be known by displaying only the summary GUI  13000  on the display device  1450  of the management computer  1400 . The load of the screen display can be alleviated since it is not necessary to display the status of all copy pairs configuring a copy group. 
     Although this embodiment explained a case where there is one copy group in the storage apparatus  1500 , the present invention can be implemented by performing the following expansion even with a plurality of copy groups. 
     For example, the management table  1522  of the storage apparatus  1500  is expanded by creating one pair status table  4000 , one summary table  5000 , and one additional information table  6000  for each copy group. In the foregoing case, the update processing  7000  of the management table  1522  may be performed for each copy group, or collectively performed for all copy groups existing in the storage apparatus  1500 . 
     In addition, the management table  1422  of the management computer  1400  is expanded by creating one copy group summary table  10000 , and one copy group pair table  11000  for each copy group. In the foregoing case, the copy group status acquisition processing  12000  may be performed for each copy group, or performed collectively for all copy groups in the storage apparatus  1500 . 
       FIG. 15  shows a display example of the summary screen  15000  displaying the results of the copy group status acquisition processing  12000  when a plurality of copy groups exist in the storage apparatus  1500 . Although the configuration of the summary screen  15000  is the same as the summary GUI  13000 , since a plurality of copy groups exist, the copy groups are displayed in a plurality of rows. 
     According to the summary GUI  15000  in this embodiment, there are a copy group  15100  named CG. 01 , a copy group  15200  named CG. 02 , and a copy group  15300  named CG. 03 , the status of the copy group CG. 01  is Pair, the concordance rate is 98%, the status of the copy group CG. 02  is Error, there is a link to the detailed GUI, and the status of the copy group CG. 03  is Copying. 
     In this embodiment, during the processing  900  to be performed by the storage apparatus  1500  upon receiving the copy pair status transfer command, the storage apparatus  1500  refers to the flag value stored in the flag field  5300  of the summary table  5000 , further refers to the transfer table determination table  8000 , and, if the flag value is failure, transfers the summary table  5000  and the pair status table  4000  from the memory  1521  to the request source. 
     Nevertheless, the present invention can be implemented without transferring the pair status table  4000  from the memory  1521  to the request source when the flag value is failure. The difference in the case of not transferring the pair status table  4000  is explained below. 
     If the copy group status is not Pair at step  12500  of the copy group status acquisition processing  12000  to be executed by the management program  1412  in the management computer  1400 , the routine does not proceed to step  12700 , and the processing is ended directly. 
     There is no change to the summary GUI  13000  displayed on the display device  1450  of the management computer  1400 , and, when the copy group status is Error, the screen display example  13500  is displayed. The copy group name displayed on the copy group name field  13100  can be clicked, and, when this is clicked, the detailed GUI example  14000  is displayed. 
     The detailed GUI example  14000  is creates based on information of the copy group pair table  11000  created in the memory  1420  of the management computer  1400 , but the update processing of the copy group pair table  11000  is performed before referring to the information. A request of the pair status table  4000  is issued from the management computer  1400  to the storage apparatus  1500 , and the pair status table  4000  is transferred from the storage apparatus  1500  to the management computer  1400 . The management computer  1400  rewrites the pair status field  4300  of the copy group pair table  11000  with the contents of the received pair status table  4000 . After this processing is complete, the management program  1412  displays the detailed GUI example  14000 . 
     Here, even if the flag value is failure, since only the summary table  5000  is transferred to the request source during the initial request, the display response of the summary GUI  13000  in the management computer  1400  can be improved. 
     Second Embodiment 
     Although the type of replication was a local copy to be performed in a single storage apparatus  1500  in the first embodiment, the type of replication is a remote copy in the second embodiment, and the present invention can be implemented by expanding the first embodiment as follows. The difference with the first embodiment is explained below. 
       FIG. 16  is a block diagram showing the configuration of a storage system in a case when the type of replication is a remote copy. In  FIG. 16 , the storage system comprises a storage apparatus  1600  for storing a secondary volume in addition to the storage apparatus  1500  for storing a primary volume. 
     The storage apparatus  1500  and the storage apparatus  1600  are mutually connected via a remote network  1900 . Although the remote network  1900  is a storage area network in this embodiment, it may also be an IP network or another data communication network. In addition, the configuration may be such that the network is partially a storage area network, and partially an IP network. The data network  1100  and the data network  1800  may also be the same network. 
     The storage apparatus  1500  and the storage apparatus  1600  comprise a remote I/F  1650  in the disk controller  1520 . The remote I/F  1650  is an interface to the remote network  1900 , and transfers data between the storage apparatus  1500  and the storage apparatus  1600 . 
     The host computer  1700  is mutually connected to the storage apparatus  1600  for storing the secondary volume via a data network  1800 . The configuration of the host computer  1700  is the same as the configuration of the host computer  1300 . Here, although the application  1312  is stored in the local disk  1310  as in the case of the storage apparatus  1500  storing the primary volume, the application  1312  may also be stored in a backup program. 
     Although the concordance rate was handled as additional information when the copy group status is Pair in the case of a local copy, primary/secondary differential time or buffer utilization (journal volume utilization) is handled as additional information in the case of a remote copy. 
     The primary/secondary differential time is a value showing the time difference between the timing that the data is written into the primary volume and the timing that the data is written into the secondary volume. In order to secure the reply performance in remote copy, there are cases where a write completion reply is returned to the host computer  1300  or  1700  at the time a data is written into the primary volume when a data write request is issued from the host computer  1300  or  1700 , and data is written into the secondary volume asynchronously with the writing of data into the primary volume. 
     This is referred to as an asynchronous remote copy. Since the time difference in the writing of data into the secondary volume depends on the network bandwidth of the remote network  1900  between the storage apparatus  1500  storing the primary volume and the storage apparatus  1600  storing the secondary volume, it is important to monitor the primary/secondary differential time. 
     In the asynchronous remote copy, when a write request is issued from the host computer  1300  or  1700 , the primary storage apparatus  1500  writes data into the volume of its own storage, and buffers the data until the writing of data into the volume of the secondary storage apparatus  1600  is complete. Buffer utilization is a value showing the usage level of the buffer. When the buffer continues to increase, or when the buffer exceeds a given value, it is possible to predict that some kind of failure will occur, and, therefore, it is important to monitor the buffer utilization. 
       FIG. 17  shows the configuration of an additional information table  17000  storing additional information of the copy group. The difference between the additional information table  17000  and the additional information table  6000  is in that the primary/secondary differential time field  17200  and the buffer utilization field  17300  are provided in substitute for the concordance rate field  6200  as additional information. 
       FIG. 18  shows the configuration of a copy group summary table  18000  storing summary information of the copy group. The difference between the copy group summary table  18000  and the copy group summary table  10000  shown in  FIG. 10  is in that a primary/secondary differential time field  18400  and a buffer utilization field  18500  are provided in substitute for the concordance rate field  10400 . According to the copy group summary table  18000 , it is evident that the copy group  18100  named CG. 01  is Pair status, the primary/secondary differential time is 2 seconds, and the buffer utilization is 15%. 
       FIG. 19  shows a display example of the summary GUI  19000  displayed on the display device  1450  of the management computer  1400 . The difference between the summary GUI  19000  and the summary GUI  13000 , a primary/secondary differential time field  19300  and a buffer utilization field  19400  are provided in substitute for the concordance rate field  13300 . 
     The difference between the processing method of the second embodiment and the processing method of the first embodiment is as follows. The processing sequence in the second embodiment regarding the update processing  7000  of the management table  1522  created in the storage apparatus  1500  is the same as the first embodiment. Nevertheless, although the concordance rate field  6200  of the additional information table  6000  was rewritten in the first embodiment during the additional information table update processing at step  7600 , the primary/secondary differential time field  17200  and the buffer utilization field  17300  of the additional information table  17000  are rewritten in the second embodiment. 
     The processing sequence in the second embodiment in the copy group status acquisition processing  12000  executed by the management program  1412  of the management computer  1400  is the same as the first embodiment, and the concordance rate field  10400  of the copy group summary table  10000  was rewritten with the contents of the received additional information table  6000  in the first embodiment during the additional information rewrite processing at step  12600 . 
     Meanwhile, in the second embodiment, the primary/secondary differential time field  18400  and the buffer utilization field  18500  of the copy group summary table  18000  are rewritten with the contents of the received additional information table  17000 . Other than the foregoing points, the second embodiment performs the same processing as the first embodiment. 
     In the second embodiment, with respect to the primary volume and the secondary volume of a plurality of copy pairs configuring a single copy group, the primary volume is stored in one storage apparatus  1500  and the secondary volume is stored in one storage apparatus  1600 . Nevertheless, the primary volume and the secondary volume of a plurality of copy pairs configuring a single copy group may also be respectively stored in a plurality of storage apparatuses. 
     In addition, although the second embodiment explains a case of connecting one storage apparatus  1500  to one host computer  1300 , it may also be connected to a plurality of host computers. 
     When a single copy group is configured across a plurality of storage apparatuses  1500 ,  1600  as described above, the present invention can be implemented by defining one storage apparatus as a representative storage apparatus, and collecting the status of all copy pairs configuring the copy group in the storage of the representative storage apparatus. 
     The second embodiment is explained on the premise that a copy group configured from a plurality of copy pairs has been preliminarily defined in the management table  1522  of the storage apparatus  1500 , and the pair status table  4000  in the storage apparatus  1500  is created based on such defined information. 
     Nevertheless, even if the copy group information is not defined in advance, the present invention can be implemented by defining which copy pairs are configuring the copy group midway during the operation. An example of the implementing the present invention by defining the copy group information midway during the operation is explained below. 
       FIG. 20  shows the configuration of a copy group definition command table  20000  to be issued from the management program  1412  of the management computer  1400  to the storage microprogram  1530  of the storage apparatus  1500 . The copy group definition command table  20000  is configured from a copy group name field  20100 , a copy pair name field  20200 , a primary volume name field  20400 , and a secondary volume name field  20500 . 
     The copy group name field  20100  displays the name of the copy group. The copy pair name field  20200  stores the name of the copy pair. Although a copy pair is uniquely identified based on the primary volume name and the secondary volume name, since this alone will make management of a copy pair difficult, a copy pair is usually managed with a logical name as the copy pair name described above. The primary volume name field  20400  stores the volume name of the primary volume of the copy pair. The secondary volume name field  20500  stores the volume name of the secondary volume of the copy pair. 
     According to the pair status table  2000  of this embodiment, the copy group CG. 01  is configured from three copy pairs; namely, a copy pair  20600  named P 1 , a copy pair  20700  named P 2 , and a copy pair  20800  named P 3 . 
     The processing flow is explained below. The management program  1412  of the management computer  1400  issues a copy group definition command to the storage apparatus  1500 . This command includes the copy group definition command table  20000 . 
     When the storage microprogram  1530  of the storage apparatus  1500  receives a copy group definition command, it creates a pair status table  4000  in the management table stored in the memory  1521 , and rewrites the copy group name field  4100 , the copy pair name field  4200 , the primary volume name field  4400 , and the secondary volume name field  4500  with the contents of the copy group definition command table  20000 . The pair status field  4300  remains a blank column. 
     As a result of taking the foregoing step, the present invention can be implemented by performing the same processing as the processing described above after the foregoing processing. Although the copy group definition command was issued from the management program  1412  in the management computer  1400  in the foregoing example, this command may also be issued from the application  1312  in the host computer  1300 . 
     Third Embodiment 
     The third embodiment is configured such that an agent computer  21100  as an auxiliary management computer is disposed between the storage apparatus  1500  and the management computer  1400 , the agent computer  21100  and the storage apparatus  1500  are connected via a collection network  21200 , the agent computer [ 21100 ] and the management computer  1400  are connected via a management network  1200 , and the management computer  1400  sends and receives data to and from the storage microprogram  1530  in the storage apparatus  1500  via the agent computer  21100 , and the remaining configuration is the same as the first embodiment. The difference with the first embodiment is explained below. 
       FIG. 21  shows the configuration of a storage system when the type of replication is a local copy. The present invention can also be implemented in a case where the type of replication is a remote copy. The configuration of the third embodiment is now explained below while focusing on the difference with the first embodiment. 
     The storage apparatus  1500  and the agent computer  21100  are connected via a data collection network  21200 . Although this embodiment explains a case where the data collection network  21200  is a storage area network, it may also be an IP network or another data communication network. 
     The agent computer  21100  and the management computer  1400  are connected via a management network  1200 . Although this embodiment explains a case where the management network  1200  is an IP network, it may also be a storage area network or another data communication network. In addition, the data network  1100  and the collection network  21200  may be the same network, and the agent computer  21100  and the host computer  1300  may be the same computer. 
     For the sake of explanation, although the third embodiment explains a case where there is one storage apparatus  1500 , one host computer  1300 , one management computer  1400 , and one agent computer, the present invention is not limited to the foregoing configuration. 
     The agent computer  21100  is configured from a CPU  21140 , a memory  21120 , a local disk  21110 , a data collection I/F  21160  for sending and receiving data and control commands to and from the storage apparatus  1500  for data collection, and a management I/F  21170  for sending and receiving data and control commands to and from the management computer  1400  for system management. 
     The local disk  21110  is a disk device such as a hard disk connected to the agent computer  21100 , and stores the management program  21112 . The management program  21112  is loaded in the memory  21120  of the agent computer  21100 , and executed by the CPU  21140 . The operation of the management program  21112  and the configuration of the management table  21122  will be described later. 
     The data collection I/F  21160  is an interface with the data collection network  212200 , and sends and receives data and control commands to and from the storage  1500 . The management table  21122  in the memory  21120  is configured from a pair status table  4000 , a summary table  5000 , and an additional information table  6000 . The configuration of the respective tables is the same as the first embodiment. 
     In the first embodiment, the copy group status determination table  3000  and the transfer table determination table  8000  were retained in the storage microprogram  1530  of the storage apparatus  1500 . In this embodiment, however, let it be assumed that these tables are retained in the management program  21112  of the agent computer  21100 . The present invention can also be implemented even when these tables are stored separately from the management program  21112 ; for instance, stored in the local disk  21110  of the agent computer  21100 . 
     In the first embodiment, the management table  1522  created in the memory  1521  of the storage apparatus  1500  was configured from a pair status table  4000 , a summary table  5000 , and an additional information table  6000 . In this embodiment, however, the management table  1522  created in the memory  1521  of the storage apparatus  1500  is configured only from the pair status table  4000 . 
     In this embodiment, the copy groups are defined via the agent computer  21100 . In other words, when a copy group is defined, the storage microprogram  1530  of the storage apparatus  1500  creates a pair status table  4000  in the management table  1522  of the memory  1521  in the storage apparatus  1500 , and the management program  21112  of the agent [computer]  21100  creates a pair status table  4000  in the management table  21122  of the memory  21120  in the agent computer  21100 . 
     Here, the storage microprogram  1530  of the storage apparatus  1500  rewrites the copy group name field  4100 , the copy pair name field  4200 , the primary volume name field  4400 , and the secondary volume name field  4500  shown in  FIG. 4  based on the information defined upon creating the pair status table  4000 . Here, the pair status field  4300  is a blank column. 
     The operation upon receiving the copy pair status transfer command to be executed by the management program  21112  in the agent computer  21100  and the microprogram  1530  in the storage apparatus  1500  is now explained with reference to the flowchart of  FIG. 22 . Although the copy pair status transfer command is issued from the management computer  1400  to the storage apparatus  1500  in the first embodiment, in this embodiment, it is issued from the management computer  1400  to the agent computer  21100 . 
     The processing of this embodiment is configured from the processing  22100  to be executed by the management program  21112  in the agent computer  21100  and the processing  22500  to be executed by the microprogram  1530  in the storage apparatus  1500 . 
     When the management program  21112  in the agent computer  21100  initially receives a copy pair status transfer command from the management computer  1400  (step  22110 ), the management program  21112  in the agent computer  21100  issues a command for acquiring the status of all copy pairs to the microprogram  1530  in the storage apparatus  1500  (step  22120 ). 
     When the microprogram  1530  in the storage apparatus  1500  receives the command for acquiring the status of all copy pairs from the management program  21112  in the agent computer  21100 , it acquires the status of all copy pairs (step  22510 ), and rewrites the pair status field  4300  of the pair status table  4000  in the memory  1521  according to the acquired status of all copy pairs (step  22510 ). 
     When the rewriting is complete, the microprogram  1530  in the storage apparatus  1500  transfers the updated pair status table  4000  to the agent computer  21100  (step  22530 ). 
     When the management program  21112  in the agent computer  21100  receives the pair status table  4000  from the microprogram  1530  in the storage apparatus  1500 , it rewrites the [pair] status table  4000  in the memory of the agent computer  21100  according to the received information (step  22130 ). 
     Subsequently, the management program  21112  in the agent computer  21100  updates the copy group status field  5200  and the flag field  5300  of the summary table  5000  based on the determination table  3000  (step  22130 ), refers to the copy group status field  5200  of the updated summary table  5000 , and checks whether the copy group status is Pair or another status (step  22150 ). 
     If the copy group status is Pair at step  22150 , the management program  21112  in the agent computer  21100  acquires the concordance rate of the copy group, stores the acquired concordance rate of the copy group in the concordance rate field  6200  of the additional information table  6000  (step  22160 ), and then ends the processing (step  22170 ). 
     If the copy group status is not Pair at step  22150 , the management program  21112  in the agent computer  21100  directly ends the processing (step  22170 ). 
     Pursuant to the enlargement of replication, needs for collectively managing a plurality of storage apparatuses  1500  installed at a location that is geographically distant with a single management computer  1400  are increasing. This embodiment meets such needs. 
     In other words, when there are a plurality of storage apparatuses  1500 , an agent computer  21100  is installed for each storage apparatus  1500 , for each storage apparatus  1500  existing in a geographically similar location. 
     According to this embodiment, since the agent computer  21100  is disposed between the storage apparatus  1500  and the management computer  1400 , and the management computer  1400  sends and receives data to and from the storage microprogram  1530  in the storage apparatus  1500  via the agent computer  21100 , it is possible to reduce the load of communication between the agent computer  21100  and the management computer  1400 , and it is also possible to reduce the load of communication for collecting information from a plurality of storage apparatuses  1500  installed at a geographically distant location. 
     Further, according to this embodiment, since a significant portion of the processing that was performed by the microprogram  1530  in the storage apparatus  1500  in the first embodiment is performed by the agent computer  21100 , it is possible to reduce the management load of the storage apparatus  1500 .