Abstract:
A method includes a configuration definition creation step of writing configuration information on a primary site into a storage subsystem; a data transfer step of copying the configuration information, which is written into a storage device, to a storage subsystem in a secondary site over a network; a data reception step of receiving the transferred configuration information and storing it in the storage subsystem in the secondary site; and a configuration definition step of reading the stored configuration information and settings up a server in the secondary site.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a recovery system in which data is transferred between storage subsystems for the purpose of preserving data in case of a disaster. 
   A technique for adding a new computer to a network is disclosed in Japanese Unexamined Patent Application Publication No. 2002-278769. The disclosed technique is particularly applicable to a case where a second computer is added to a network system that comprises a first computer, a first storage subsystem in which an operating system (hereinafter OS) is stored, and a second storage subsystem in which a copy of data stored in the first storage subsystem is stored. According to the technique, the first computer modifies the settings of the second storage subsystem, and it assigns the second storage subsystem to the second computer so that the OS stored in the second storage subsystem can be installed in the second computer. 
   Moreover, a method for setting up a high-availability system, which employs a common disk, in a storage subsystem is disclosed in “VERITAS Cluster Volume Manager and VERITAS Cluster File System: a new VERITAS volume management and file system technology for a cluster environment (http://www.veritas.com/jp/products/pdfs/cvm_cfs_wp.pdf)”. According to this method, a slave computer detects a common disk included in a storage subsystem, and it reads volume information from the common disk so as to define a common volume to be assigned to a slave computer included in a high-availability configuration. Consequently, the slave computer included in the high-availability configuration autonomously recognizes the volume. 
   SUMMARY OF THE INVENTION 
   According to the technology disclosed in Japanese Unexamined Patent Application Publication No. 2002-278769, after the second computer is added, the first computer modifies the settings of the second storage subsystem. In this case, if a fault occurs in the first computer, the second computer cannot use the second storage subsystem. Moreover, if the network system is used as a disaster recovery system, both the first and second computers are mandatory. Therefore, an inexpensive disaster recovery system cannot be provided. 
   Moreover, according to the technology disclosed in “VERITAS Cluster Volume Manager and VERITAS Cluster File System: a new VERITAS volume management and file system technology for a cluster environment,” the slave computer can recognize the common volume autonomously. However, the master computer and slave computer must share the same storage subsystem. Therefore, the technology cannot be adapted to a disaster recovery system as it is. The adaptation of the technology disclosed in “VERITAS Cluster Volume Manager and VERITAS Cluster File System: a new VERITAS volume management and file system technology for a cluster environment” to a disaster recovery system will be discussed. 
   As far as a disaster recovery system is concerned, an entity of a disk drive is often different between a primary site and a secondary site. The consistency in an emulation type that is a category to which a disk drive belongs when assigned to a computer or in a storage capacity of a disk drive between the primary and secondary storage systems is not guaranteed. In this situation, the computer in the secondary site cannot recognize a volume autonomously. 
   Moreover, when an application, such as a database application that runs in the primary site, is to be continuously run in the secondary site, the settings of the secondary site must be determined manually. It is therefore impossible to continuously and swiftly run the application. 
   Accordingly, the present invention provides the constituent features described below. Namely, a computer system comprises a first computer, a first storage subsystem connected to the first computer, and a second storage subsystem connected to the first storage subsystem. Herein, information and various environmental variables (hereinafter, referred to as configuration information) that are needed to use the first storage subsystem and that are held in the first computer are transmitted to the first storage subsystem. The first storage subsystem stores the received configuration information in a storage device included therein. Thereafter, the first storage subsystem transfers the configuration information, which is stored therein, to the second storage subsystem so as to produce a copy. The second storage subsystem receives the transferred configuration information and stores it in a storage device included therein. Furthermore, when a second computer is added to the computer system, the second computer reads the configuration information stored in the second storage subsystem and determines the settings thereof by itself. 
   Herein, when it is indicated that the settings of the second computer are determined by itself, it is meant that a storage area included in the storage subsystem is assigned or mounted, and that definition information used in various applications is read. 
   Incidentally, the configuration information contains definition information needed to run an application and information needed to mount a storage area or a volume in a computer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram which shows an example of the configuration of a computer system; 
       FIG. 2  is a diagram which shows an example of a pair definition table  7 ; 
       FIG. 3  is a diagram which shows an example of a volume definition table  8 ; 
       FIG. 4  is a diagram which shows an example of a configuration definition table  9 ; 
       FIG. 5  is a flow diagram which shows describes an example of a data receiving procedure; 
       FIG. 6  is a flow diagram which shows an example of a procedure designated as a component definition program  12 ; 
       FIG. 7  is a diagram which shows an example of the pair definition table  7  specifying a suspended state; 
       FIG. 8  is a flow diagram which shows an example of a volume mounting procedure; 
       FIG. 9  is a diagram which shows examples of a volume-device file map; and 
       FIG. 10  is a diagram which shows an example of a mount destination directory-device file map. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1  to  FIG. 10 , an embodiment of the present invention will be described.  FIG. 1  shows the configuration of an embodiment of a computer system. The system comprises a server  1   a , a server  1   b , a storage subsystem  2   a , and a storage subsystem  2   b . The servers and systems are interconnected over a network  3 . The server  1   b  may be, as described later, a computer connected on the network  3  later. 
   As far as the present system is concerned, the server  1   a  and storage subsystem  2   a  shall constitute a primary site, while the server  1   b  and storage subsystem  2   b  shall constitute a secondary site. 
   The server  1  is a computer comprising a CPU  101 , a main memory  102 , a network interface  103 , a display  104 , a keyboard  105 , a CD-ROM  106 , a controller  107 , a disk drive  108 , and a data interface  109 . 
   The storage subsystem  2  is realized with storage devices in which data is stored, and it comprises ports  21 , a disk controller  22 , a control memory  23 , a processor  24 , a cache memory  25 , and disk drives  26 . Incidentally, the disk drives  108  and  26  are logical storage devices. In reality, a plurality of physical storage devices may constitute one logical storage device. In this case, the plurality of physical storage devices may constitute a disk array. Herein, the physical storage device refers to a hard disk drive or a physical storage device having a storage medium such as a digital versatile disk (DVD). 
   A database management system program  4 , an application program  5 , a configuration definition file creation program  6 , and a volume mount program  18  are stored in the disk drive  108  included in the server  1 . These programs are installed from the CD-ROM  106  into the disk drive  108 , then read into the main memory  102 , and run by the CPU  101 . Incidentally, the programs need not be installed from the CD-ROM  106 , but may be installed into the disk drive  108  over the network  3  on which the server  1  is connected. 
   A pair definition table  7  used to manage the relationship of correspondence (hereinafter, pair relationship) between each of the disk drives  26  included in the primary site and each of the disk drives  26  included in the secondary site, a volume definition table  8   a  used to manage one or more disk drives  26  (one or more of disk drives  26   a  to  26   c ) as one or more storage areas (hereinafter volumes), and a data transfer program  16  that is run by the processor  24   a  when data stored in any of the disk drives  26  is transferred to the storage subsystem  2   b  in the secondary site are stored in the control memory  23   a  included in the storage subsystem  2   a.    
   A configuration definition table  9 , indicating to what part of an OS file system a volume is assigned (hereinafter, mounted), is stored in the disk drive  26  whose leading location corresponds to the leading position in the volume, or a predetermined location in a volume. Hereinafter, the configuration definition table shall be stored at the leading location in the volume. The primary and secondary sites share the stored location. The secondary site receives information on the stored location from the primary site or a user. Moreover, an environmental variable definition file  15  in which the name of a definition information file is registered is stored in the disk drive  26  realizing the volume. Herein, setting information on the database management system program  4  or application program  5  that run on the server  1  which uses the volume is recorded in the definition information file. Information on the stored location of a file in which information on an environmental variable relevant to the server  1 , such as, setting information on a program to be run in the server  1  is recorded, is registered in the environmental variable definition file  15 . 
   According to the present embodiment, a file system in which the volume is mounted gives a predetermined name to the environmental variable definition file  15 . A value recorded in the environmental variable definition file  15  indicates a name inherent to the application program  5  or the like, and the name need not be a filename, but may be, for example, a work directory name. 
   A DBMS definition information file  10 , that is a definition information file relevant to the database management system program  4 , and an application definition information file  13 , that is a definition information file relevant to the application program  5 , are stored in the disk drives  26 . The files are assigned filenames that are registered in the environmental variable definition file  15  and stored in the disk drives  26 . 
   The server  1  runs the configuration definition file creation program  6  so as to create the environmental variable definition file  15  and program definition information files. 
   Moreover, data  14  used within the database management system program  4  and application program  5  are stored in the disk drives  26 . Furthermore, the database management system program  4 , application program  5 , and configuration definition file creation program  6  may be stored in the disk drives  26  included in the storage subsystem  2   a . In this case, when the server  1  uses the programs, the server  1  reads the programs from the storage subsystem  2  over the network  3 , and stores them in the disk drive  108  for use. 
   A data reception program  17 , a pair definition table  7 , a volume definition table  8   b , and a definition check program  11  are stored in the control memory  23   b  included in the storage subsystem  2   b.    
   When the storage subsystem  2   b  receives data sent from the storage subsystem  2   a  via the port  21   d  over the network  3  and stores the data in the disk drives  26   d  to  26   f , the processor  24   b  runs the data reception program  17 . 
   The definition check program  11  judges whether data the storage subsystem  2   b  has received from the storage subsystem  2   a  is contained in the configuration definition table  9 . If the data is contained in the configuration definition table  9 , when the contents of a configuration definition are checked, the processor  24   b  runs the definition check program  11 . 
   Copies of the configuration definition table  9 , environmental variable definition file  15 , DBMS definition information  10 , application definition information  13 , and data that are stored in the disk drives  26  included in the storage subsystem  2   a  are stored in the disk drives  26   d  to  26   f.    
     FIG. 2  shows an example of the structure of the pair definition table  7 . The pair definition table  7  has: a group name field  201  in which names of groups each of which corresponds to a set of pair relationships are registered; a pair name field  202  in which names assigned to pair relationships are registered; a primary port name field  203  in which names assigned to the ports of the storage subsystem  2   a  included in the primary site that have a pair relationship are registered; a primary logical unit name field  204  in which names assigned to logical units in the storage subsystem  2   b  included in the secondary site that have a pair relationship are registered; a secondary port name field  205  in which names assigned to the ports of the storage subsystem  2   b  included in the secondary site that have a pair relationship are registered; a secondary logical unit name field  206  in which names assigned to logical units in the storage subsystem  2   b  included in the secondary site that have a pair relationship are registered; and a state field  207  in which the states of pair relationships are registered. 
   The logical unit (LU) is a unit in which the storage areas formed with the disk drives  26  are managed. Moreover, a volume is uniquely identified with a combination of the name of a port via which an LU is accessed and the name of the LU associated with the volume. Hereinafter, a port name and an LU name will be used to express a volume as a volume (port name, LU name). According to the present embodiment, one LU is associated with one volume. Alternatively, a plurality of LUs may constitute one volume. 
   In the example of  FIG. 2 , a group G 1  having two pair relationships P 1  and P 2  is defined. A record  208   a  indicates that a volume in the primary site having the pair relationship P 1  is a volume (port  21   b , LU 0 ), a volume in the secondary site having the pair relationship P 1  is a volume (port  21   d , LU 0 ), and the state of the pair relationship is active. Herein, the active state signifies that copying data between the pair indicated with the record  208 , that is, making the data items in the primary and secondary sites consistent with each other, is under way. Moreover, a record  208   b  indicates that a volume in the primary site having the pair relationship P 2  is a volume (port  21 , LU 1 ), a volume in the secondary site having the relationship P 2  is a volume (port  21   d , LU 1 ), and the state of the relationship is active. 
     FIG. 3  shows an example of the structure of the volume definition table  8 . A user creates the volume definition table  8  using a volume definition program in advance. Herein, the volume definition program is a program to be run in a management computer (not shown) connected on the network  3 . The user uses the management computer to transmit information on volumes, which should be included in the storage subsystem  2 , to the storage subsystem  2 . 
   The storage subsystem  2  registers the received information in the volume definition table  8 . The volume definition table  8  has: a port name field  305  in which names of ports, based on which volumes are identified, are registered; an LU name field  301  in which names of LUs forming volumes are registered; a drive name field  302  in which names of disk drives  26  realizing the volumes are registered; and an emulation type field  303  in which pieces of information on the ways (hereinafter, emulation types) a computer employs a volume are registered. 
   According to the present embodiment, for example, a volume definition table  8   a  shown in the upper part of  FIG. 3  shall be stored in the control memory  23   a , and a volume definition table  8   b  shown in the lower part of  FIG. 3  shall be stored in the control memory  23   b . In the volume definition table  8   a  shown in  FIG. 3 , two volumes are registered. A record  304   a  indicates that a volume (port  21   b , LU 0 ) is realized with the disk drive  26   a , and it is not categorized to any specific emulation type. Records  304   b  and  304   c  indicate that a volume (port  21   b , LU 1 ) is realized with the disk drives  26   b  and  26   c  and categorized to an emulation type of RAID level 1. 
   On the other hand, two volumes are registered in the table  8   b . A record  304   d  indicates that a volume (port  21   d , LU 0 ) is realized with the disk drive  26   d  and is not categorized to any specific emulation type. Records  304   e  and  304   f  signify that a volume (port  26   d , LU 1 ) is realized with the disk drives  26   e  and  26   f  and categorized to the emulation type of RAID level 1. 
     FIG. 4  shows an example of the structure of the configuration definition table  9 . In the case of the storage subsystem  2   a  in the primary site, when the server  1   a  runs the volume mount program  18 , the configuration definition table  9  is created. In the case of the storage subsystem  2   b  in the secondary site, when the storage subsystem  2   b  writes the configuration definition table  9 , which is received from the storage subsystem  2   a  in the primary site, in a volume, the configuration definition table  9  is created. 
   The configuration definition table  9  has: a mount destination field  401  in which information on a directory in which a volume is mounted is registered; a storage capacity field  402  in which information on the storage capacity of the volume is registered; and an emulation type field  403  in which information on an emulation type is registered. 
   A table  9   a , as shown in the upper part of  FIG. 4 , is an example of the configuration definition table  9  stored in a volume (port  21   d , LU 0 ) (realized with the disk device  26   a ) in the storage subsystem  2   a . The information that the mount destination of a volume (port  21   d , LU 0 ) is a directory /AP/vol1, the storage capacity thereof is 100 MB, and the volume is not categorized to any specific emulation type is registered as a record  404   a . Incidentally, the expression /AP/vol1 of an access path in a file system shall be adopted as the expression of a file or a directory in the file system. 
   A table  9   b , as shown in the lower part of  FIG. 4 , is an example of the configuration definition table  9  stored in a volume (port  26   d , LU 1 ) (realized with the disk drives  26   a  and  26   b ) in the storage subsystem  2   a . The information that the mount destination of a volume (port  26   d , LU 1 ) is a directory /DB/vol1, the storage capacity thereof is 200 MB, and the volume is categorized to an emulation type of RAID level 1 is registered as a record  404   b.    
   Referring to  FIG. 1 , the actions of the present system will be outlined below. To begin with, a user uses a management computer to specify values in the volume definition table  8   a  in the storage subsystem  2   a  in advance. 
   Thereafter, when the server  1   a  is started up, the server  1   a  mounts a volume, which is included in the storage subsystem  2   a , in a file system. At this time, the server  1   a  creates the configuration definition table  9  that has configuration information indicating the relationship of the volume to the file system that is the mount destination, and it stores the configuration definition table  9  in the disk drive  26  realizing the volume. 
   Thereafter, the server  1   a  creates the DBMS definition information  10  that constitutes a definition information file to be used to run the database management system program  4   a , and the application definition information  13  that constitutes a definition information file to be used to run the application  5   a . The server  1   a  then stores the created pieces of information in the volume. Moreover, the server  1   a  creates the environmental variable definition file  15  as a file in which information on the stored locations in the storage subsystem  2   a  of environmental variables, such as those contained in the definition information files, is registered. The server  1   a  stores the file  15  in the volume included in the storage subsystem  2   a.    
   In order to configure the secondary site, a user connects the storage subsystem  2   b  included in the secondary site on the network  3  and uses the management computer to create the volume definition table  8   b  concerning the storage subsystem  2   b  and to register values in the table. Thereafter, the server  1   a  directs the storage subsystem  2   a  to transfer data items, which are stored in the disk drives  26   a  to  26   c , to the storage subsystem  2   b . Consequently, the configuration definition tables  9 , environmental variable definition file  15 , application definition information  13 , DBMS definition information  10 , and data  14  stored in the disk drives  26   a  to  26   c  are stored in the storage subsystem  2   b  in the secondary site. 
   For the data transfer, the storage subsystem  2   b  checks if the configuration definition table  9  is included in the transferred data items and if the configuration definition table  9  matches the situation of the associated volume included in the storage subsystem  2   b . If the configuration definition table  9  does not match the situation, the storage subsystem  2   b  does not preserve the configuration definition table  9  in the disk drive  26  concerned. 
   When the server  1   b  is connected on the network  3  and started up, the server  1   b  runs a configuration definition program  12  so as to recognize the volume included in the storage subsystem  2   b  and mount the volume. 
   At this time, the server  1   b  reads the configuration definition table  9   a  from the disk drive  26  so as to acquire a directory name that is the mount destination of the volume realized with the disk drive  26 . Based on the acquired mount destination directory name, the volume is mounted. Incidentally, the server  1   b  references the pair definition table  7  so as to retrieve a group name, of which pair relationships are all suspended, as an object of the mount. 
   Thereafter, the server  1   b  acquires the environmental variable definition file  15  from the mounted volume, and it checks the file  15  for the stored locations of various definition information files. The server  1   b  then initiates the database management system program  4   b  and application program  5   b . Consequently, once the server  1   b  reads the configuration information such as the configuration definition table  9 , the server  1   b  can acquire setting information relevant to a file system serving as the mount destination of the volume and setting information relevant to an application that uses the volume. Without the server  1   a , a volume can be mounted or an application can be set up. The detailed procedure of the foregoing actions will be described in conjunction with the drawings. 
     FIG. 8  illustrates a procedure  1000  for mounting a volume by running the volume mount program  18  in the CPU  101 . First, the server  1  acquires from a user the name of a directory in which a volume is mounted (hereinafter a mount destination directory name) and a device filename indicating the volume to be mounted. 
   Within an application program or a file system a user employs, a volume is recognized with a device filename, as will be described later. The server  1  references a volume-device file map that will be described later to retrieve information on a port and an LU, with which a predetermined volume is determined, on the basis of the device filename. Using the information, the volume included in the storage subsystem  2  is designated (step  1001 ). 
   Thereafter, the server  1  checks if the configuration definition table  9  is stored at the leading location in the volume designated with the device filename. Specifically, the server  1  transmits information on the designated volume (more particularly, the port name and LU name), and it also transmits a command requesting the configuration definition table  9  to the storage subsystem  2 . The server  1  then receives the result of the transmission from the storage subsystem  2 . Incidentally, the server  1  acquires the information concerning the stored location of the configuration definition table  9  (the leading location in a volume according to the present embodiment) from any other server  1  or by receiving a user&#39;s entry. Consequently, in response to the command requesting the configuration definition table  9 , the server  1  transmits the configuration definition table  9  together with the information on the stored location. However, the storage subsystem  2  may have the information on the stored location of the configuration definition table  9 . In this case, the server  1  merely transmits the command requesting the configuration definition table  9  to the storage subsystem  2  (step  1005 ). 
   If the configuration definition table  9  is not stored in the user-designated volume, the server  1  first references the volume definition table  8  to retrieve the storage capacity of the designated volume and the emulation type thereof from the size field  306  and emulation type field  303 , respectively. Specifically, the server  1  designates the volume in the storage subsystem  2 , requests the storage subsystem  2  to transmit information on the storage capacity of the volume and the emulation type thereof, and receives the information (step  1002 ). 
   Thereafter, the server  1  creates the configuration definition table  9  on the basis of the mount destination directory name of the volume, the storage capacity thereof, and the emulation type thereof, and it transmits the table to the storage subsystem  2 . The stored location of the configuration definition table  9  is the leading location in the designated volume. Specifically, the server  1  transmits the information on the mount destination directory name, storage capacity, and emulation type to the storage subsystem  2 , and directs the storage subsystem  2  to write the information at the leading location in the designated volume. At this time, the server  1  creates the environmental variable definition file  15  relevant to the designated volume, and it directs the storage subsystem  2  to store the file in the designated volume (step  1003 ). 
   Finally, the server  1  mounts the designated volume in a place determined with the mount destination directory name acquired at step  1001  or with the mount destination direction name designated by the server  1  (step  1004 ). If it is judged at step  1005  that the configuration definition file  9  is present, the server  1  executes step  1004  described above. 
     FIG. 5  describes an example of a procedure to be achieved by running the data reception program  17  and definition check program  11  in the storage subsystem  2   b . The storage subsystem  2   b  executes the procedure to check the contents of information sent from the storage subsystem  2   a.    
   Incidentally, every time data is transferred between the storage subsystems  2 , information on a port name in the primary site and information on an LU name and its location therein are appended to the data. The storage subsystem  2   b , having received the data, references the primary port field  203  and primary LU field  204  of the pair definition table  7  to retrieve a record  208  that contains the same port name and volume name as those contained in the received data. The storage subsystem  2   b  then designates a volume, which is determined with the values that are specified in the secondary port name field  205  and secondary LU name field  206  and that are contained in the record  208 , as a volume in which the received data is stored. Furthermore, the storage subsystem  2   b  determines the stored location in the volume, in which the data is stored, according to the value of position information contained in the received data. Incidentally, when a volume is realized with disk drives  26  that constitute a RAID disk drive, the storage subsystem  2  determines uniquely at what location in whichever of the disk drives  26  data is recorded. 
   The storage subsystem  2   b  having received data first verifies whether the received data contains the configuration definition table  9 . Specifically, if the configuration definition table  9  is stored at the leading location in a volume, the storage subsystem  2   b  verifies whether the configuration definition table  9  is contained in the received data by checking whether the leading data in the volume has been sent from the storage subsystem  2   a . Whether the leading data in the volume has been sent from the storage subsystem  2   a  is judged from information on a location contained in transferred data. 
   Incidentally, the storage subsystem  2   b  receives information on the stored location of the configuration definition table  9  from the primary site or a user in advance. Specifically, the storage subsystem  2   b  receives the information on the stored location transferred from the server  1   a  in the primary site. Otherwise, the storage subsystem  2   b  receives the information on the stored location which a user registers at the time of registering a volume definition table using the management terminal (step  601 ). 
   If the received data contains the configuration definition table  9 , the storage subsystem  2   b  checks if the storage capacity of a volume in which the transferred configuration definition table  9  is stored is larger than the storage capacity registered in the field  402  of the configuration definition table  9 . Incidentally, the storage subsystem  2   b  references the pair definition table  7  on the basis of the information on the volume (port name and LU name) that is transferred together with the configuration definition table  9 . Thereafter, the storage subsystem  2   b  references the volume definition table  8   b  so as to retrieve the value specified in the size field  306  and contained in a record that contains the information on the volume (step  602 ). 
   Assume that the storage capacity of the volume in which the configuration definition table  9  is stored is larger than the storage capacity registered in the field  402 . In this case, the storage subsystem  2   b  checks if the value registered as the emulation type of the volume in the volume definition table  8   b  agrees with the value registered in the emulation type field  403  of the transferred configuration definition table  9  (step  603 ). If the values agree with each other, the transferred configuration definition table  9  is stored in the volume. If it is judged at step  601  that the configuration definition table  9  has not been transferred, the storage subsystem  2  stores the transferred data in the volume (step  604 ). 
   In contrast, it may be judged at step  602  that the storage capacity of the volume is smaller than the one registered in the field  402 , or it may be judged at step  603  that the emulation types are different from each other. In this case, the storage subsystem  2   b  does not store the transferred data in the disk device  26 , but terminates the procedure. 
     FIG. 6  shows a configuration definition procedure that is executed in the storage subsystem  2   b  by running the configuration definition program  12  in the server  1   b . The present procedure enables the server  1   b  to run the application program  5  or the like using the volumes included in the storage subsystem  2   b . The present procedure is executed, for example, when the server  1   b  is connected on the network  3  and started up, or when a user enters a volume mount command at the server  1   b.    
   To begin with, the server  1   b  acquires the information on all the ports and all the LUs, which are included in the storage subsystem  2   b  accessible to the server  1   b , from the storage subsystem  2   b . The items of information are associated with device files managed by a file system residing in the server  1   b . Data representing the relationship of correspondence between each item of information and each device file, that is, a volume-device file map  1101 , as shown in  FIG. 9 , is stored in the main memory  102  or one of the storage devices  108  (step  704 ). 
   Thereafter, the server  1   b  checks the state field  207  of the pair definition table  7  included in the storage subsystem  2   b  to see if there is a group having pair relationships whose states are all suspended. Incidentally, what is referred to as a suspended state is a state in which the contents of data items in volumes having a pair relationship to each other are not kept consistent with each other (step  701 ). If there is a group having pair relationships whose states are all suspended, the server  1   b  references the pair definition table  7  included in the storage subsystem  2   b  to retrieve the values that are registered in the secondary port name field  205  and secondary LU name field  206  in relation to the group name (step  702 ). 
   Thereafter, the server  1   b  references the maps created at step  704  so as to retrieve device files associated with the volumes determined with the port names and LU names acquired at step  702 . On the other hand, the server  1   b  reads the configuration definition table  9  from the leading location in each of the volumes associated with the device files. The server  1   b  then retrieves information on the mount destination directory name of each of the volumes from the field  401  of the configuration definition table  9  (step  703 ). 
   Thereafter, the server  1   b  uses the retrieved device filenames and mount destination directory names as arguments to run the volume mount program  18 , and, thus, it mounts the volumes in the file system that is a mount destination (step  1000 ). After mounting all the volumes that belong to the group having pair relationships, whose states are all suspended, is completed, the server  1  acquires the environmental variable definition file  15  from each of the mounted volumes, and it checks the values registered in the environmental variable definition files  15  (step  705 ). 
   Thereafter, the server  1   b  starts running the database management system program  4   b  and application program  5   b . At the time running of the database management system program  4   b  and application program  5   b  is started, the server  1   b  identifies the location of a definition information file on the basis of the information registered in each of the environmental variable definition files  15  acquired previously. The server  1   b  then acquires the definition information files (step  706 ). 
   A description will be made of a case where the configuration information present in the primary site included in the system shown in  FIG. 1  (according to the present embodiment, the configuration definition tables, environmental definition information files, and various program definition information files) and data are transferred to the storage subsystem  2   b  in the secondary site. Herein, the pair definition table  7  shown in  FIG. 2  and the volume definition table  8   a  shown in  FIG. 3  shall be present in the control memory  23   a  included in the storage subsystem  2   a . Moreover, the pair definition table  7  shown in  FIG. 2  and the volume definition table  8   b  shown in  FIG. 3  shall be present in the control memory  23   b  included in the storage subsystem  2   b.    
   When the server  1   a  connected on the network  3  is started up, the server  1   a  acquires information on the volumes, which are included in the storage subsystem  2   a  connected to the data interface  109   a , from the storage subsystem  2   a . The items of information are associated with device files and stored as the volume-device file map  1101   a . The volume-device file map  1101   a  is stored in the main memory  102  included in the server  1   a .  FIG. 9  shows examples of the volume-device file maps  1101 . In the present case, a volume (port  21   b , LU 0 ) is associated with a device file whose name is /dev/cltld1, and a volume (port  21   b , LU 1 ) is associated with a device file whose name is /dev/cltld2. 
   Thereafter, the server  1   a  receives mount destination directory names in which the volumes are mounted and device filenames associated with the mounted volumes from a user or an application. The server  1   a  then runs the volume mount program  18  (step  1000 ). 
     FIG. 10  shows an example of information which the server  1   a  receives from a user as a mount destination directory-device file map  1201 . The server  1   a  having received the mount destination directory-device file map  1201  judges from a record  1202   a  that the volume associated with the device file /dev/cltld1 is mounted in the directory /AP/vol1. The server  1   a  also judges from a record  1202   b  that the volume associated with the device file /dev/cltld2 is mounted in the directory /DB/vol1 (step  1001 ). 
   Thereafter, the server  1   a  verifies whether the configuration definition table  9  is stored in each of the volumes designated with the device filenames. First, the server  1   a  verifies whether the configuration definition table  9  is stored in the volume designated with /dev/cltld1. The server  1   a  retrieves information on a port that determines the designated volume, or more particularly, the port name of port  21   b  and the LU name of LU 0 , from the volume-device file map  1101   a . The server  1   a , having acquired the items of information, accesses the storage subsystem  2   a  using the items of information. The server  1   a  then judges whether the configuration definition table  9  is stored at the leading location in a disk drive  26  comparable to the leading location in the volume. In this case, the configuration definition table  9  has not yet been stored in the volume. The server  1   a  therefore judges that the configuration definition table  9  is absent (step  1005 ). 
   Thereafter, the server  1   a  references the volume definition table  8   a  to retrieve the emulation type and size of the volume to be mounted. In the present case, the server  1   a  references the emulation type field  303  and size field  306  so as to retrieve values contained in a record  304   a  that has the port name of port  21   b  and LU name of LU 0  specified in the port name field  305  and LU name field  301 , respectively. Consequently, the server  1   a  acquires the information that the volume to be mounted is not categorized into any emulation type and has a storage capacity of 100 MB (step  1002 ). 
   Thereafter, the server  1   a  enters the acquired mount destination directory name (/AP/vol1), emulation type (none), and size (100 MB) in the mount destination field  401 , emulation type field  403 , and storage capacity field  402  of the configuration definition table  9   a . Thereafter, the server  1   a  transmits the created configuration definition table  9   a  to the storage subsystem  2   a , and it directs the storage subsystem  2   a  to store the configuration definition table  9   a  at the leading location in the volume to be mounted. In the present case, the value contained in the record  304   a  and specified in the drive field  302  of the volume definition table  8   a  shown in  FIG. 3  demonstrates that the disk drive  26  realizing the volume is the disk drive  26   a . Consequently, the configuration definition table  9   a  is disposed at the leading location in the disk drive  26   a  (step  1003 ). 
   Thereafter, the server  1   a  mounts the volume (port  21   b , LU 0 ) associated with the device file /dev/cltld1 in a location designated with the acquired mount destination directory name (step  1004 ). 
   The server  1   a  performs the same processing on a volume associated with a device filename contained in a record  1202   b . The server  1   a  directs the storage subsystem  2   a  to store the configuration definition table  9   b  shown in  FIG. 4  at the leading location in volume (port  21   b , LU 1 ), and then it mounts volume (port  21   b , LU 1 ) in a place designated with /DB/vol1. 
   In the present case, the values contained in the records  304   b  and  304   c  and specified in the drive field  302  of the volume definition table  8   a  shown in  FIG. 3  demonstrate that the volume is realized with the disk drives  26   b  and  26   c . If a volume is realized with a plurality of disk drives  26 , whichever of the leading locations in the disk drives corresponds to the leading location of a volume is determined by the storage subsystem  2   a . In this case, the leading location in the disk drive  26   b  corresponds to the leading location of the volume. Therefore, the configuration definition table  9   b  is stored at the leading location in the storage area of the disk drive  26   b.    
   Thereafter, the server  1   a  transmits information on a stored location of environmental variables defined by the server  1   a , or, more particularly, a stored location of an application definition information file, to the storage subsystem  2   a . At this time, the server  1   a  directs the storage subsystem  2   a  to create an environmental variable definition file  15  having a predetermined filename in a mounted volume and to record the transmitted information in the file  15 . According to the present embodiment, the filename of the environmental variable definition file  15  shall be /AP/vol1/env.txt, and the stored location thereof shall be a location in the disk drive  26   a . According to the present embodiment, the information that a DBMS configuration definition information file is stored as a file /DB.vol1/db.conf and an AP configuration definition information file is stored as a file /AP/vol1/ap.conf is registered in the environmental variable definition file  15  (step  501 ). 
   Thereafter, the server  1   a  transmits the definition information files relevant to the database management system  4   a  and application  5   a , respectively, to the locations registered in the environmental variable definition file  15 . In the present case, the definition information  10  on the database management system  4   a  is stored as a file /DB/vol1/db.conf, and the definition information  13  on the application program  5   a  is stored as a file /AP/vol1/ap.conf. The volume mounted in /DB/vol1 is realized with the disk drives  26   b  and  26   c . However, the DBMS definition information  10  is stored in the disk drive  26   b . Moreover, as the volume mounted in /AP/vol1 is realized with the disk drive  26   a , the application definition information  13  is stored in the disk drive  26   a  (step  502 ). 
   Next, a description will be made of a procedure for transferring data, which is stored in the disk drives  26   a  to  26   c  included in the storage subsystem  2   a , to the disk drives  26   d  to  26   f  included in the storage subsystem  2   b  over the network  3 . The data transfer is executed after the pair definition table  7  is created. The procedure is started at the time that a user uses the server  1  or the like to direct the storage subsystem  2   a  to transfer data. 
   The storage subsystem  2   a  appends information on the ports and LUs included therein and information on stored locations of data items to the data items stored in the disk drives  26   a  to  26   c , respectively, and it transfers the resultant data items to the storage subsystem  2   b . After data transfer is completed, the data items stored in the disk drives  26   a  to  26   c , respectively, may be updated. In this case, if the contents of data items in the storage subsystems  2   a  and  2   b  are kept consistent with each other, the storage subsystem  2   a  transfers updated data alone to the storage subsystem  2   b.    
   The storage subsystem  2   b  having received data from the storage subsystem  2   a  executes the procedure illustrated in  FIG. 5 . First, the storage subsystem  2   b  judges whether the configuration definition table  9  has been transferred from the storage subsystem  2   a . Specifically, the transferred data is checked to see if it is the data stored at the leading location in a volume. Whether the transferred data is the data stored at the leading location in a volume is judged by checking to see if position information appended to the transferred data is 0 (step  601 ). 
   If the configuration definition table  9   a  shown in  FIG. 4  is transferred, the storage subsystem  2   b  runs the definition check program  11  so as to acquire the information on the port and LU included in the storage subsystem  2   a  which is appended to the transferred data. In the present case, the information that the port name is port  21   b  and the LU name is LU 0  is acquired. Thereafter, the storage subsystem  2   b  retrieves the record  208   a , which contains port  21   b  and LU 0  as the values of the primary port name field  203  and primary LU name field  204 , from the pair definition table  7  stored in the control memory  23   b . The storage subsystem  2   b  then acquires the values (herein, port  21   d  and LU 0 ) specified in the secondary port name field  205  and secondary LU name field  206  from the record  208   a.    
   Thereafter, the storage subsystem  2   b  acquires the record  304   d  that contains port  21   d  and LU 0  as the values of the port name field  305  and LU name field  301 , respectively, of the volume definition table  8   b . The storage subsystem  2   b  then compares the value of 100 MB, which is contained in the record  304   d  and specified in the size field  306 , with the value of 100 MB that is contained in the record  404   a  and specified in the storage capacity field  402  of the configuration definition table  9  (step  602 ). Since the values agree with each other, the storage subsystem  2   b  checks to see if the value contained in the record  304   d  and specified in the emulation type field  303  agrees with the value contained in the record  404   a  and specified in the emulation type field  403  (step  603 ). 
   Since the values agree with each other and signify that the volume is not categorized into any emulation type, the storage subsystem  2   b  stores the transferred data in the volume (port  2   d , LU 0 ). The stored location is represented by position information appended to data. 
   The foregoing procedure is repeated for every data item to be transferred. Consequently, the configuration definition tables  9 , environmental variable definition file  15 , application definition information  13 , DBMS definition information  10 , and data  14  that are stored in the disk drives  26   a  to  26   c  included in the storage subsystem  2   a  in the primary site are copied into the disk drives  26   d  to  26   f  included in the storage subsystem  2   b  in the secondary site. Moreover, after the data items are copied, if the data in any of the disk drives  26   a  to  26   c  in the primary site is updated, the change is reflected in the associated one of the disk drives  26   d  to  26   f  in the secondary site. 
   Next, a description will be made of an example of a procedure for connecting the port  21   d  of the storage subsystem  2   b  in the secondary site to the data interface  109  in the server  1   b  over the network  3 , starting up the server  1   b , and determining the environment of the server  1   b.    
   When the server  1   b  is started up, the configuration definition program  12  is read into the main memory  102   b  and run by the CPU  101   b . First, the server  1   b  associates the ports and LUs, which are included in the storage subsystem  2   b  accessible to the server  1   b , with device files. In this example, the LUs accessible via the port  21   d  are the two LUs LU 0  and LU 1  alone. Device filenames determined by the file system residing in the server  1   b  are associated with the LUs. A created volume-device file map is the one  1101   b  shown in  FIG. 9 . Referring to  FIG. 9 , a volume (port  21   d , LU 0 ) is associated with /dev/cltld1, and a volume (port  21   d , LU 1 ) is associated with /dev/cltld2. 
   Thereafter, the server  1   b  references the state field  207  of the pair definition table  7  present in the control memory  23   b  included in the storage subsystem  2   b  to check the pair relationships of the volumes. Specifically, the server  1   b  checks to see if there is a group having pair relationships, whose states are all suspended, as specified in the field  207  represent the state. If the pair definition table  7  is as shown in  FIG. 2 , the server  1   b  judges that there is a record containing a value that is not “suspended,” and it repeats the processing of step  701 . 
   If a fault occurs in the primary site, the pair relationships are all suspended.  FIG. 7  shows the pair definition table  7  signifying this state. In this example, records  208   a  and  208   b  demonstrate that all the pair relationships belonging to group G 1  are suspended. Consequently, the server  1   b  judges that the pair relationships belonging to group G 1  are all suspended. 
   Thereafter, the server  1   b  retrieves from the pair definition table  7  the information on the volumes relevant to the group having pair relationships whose states are all suspended. In this case, the server  1   b  acquires the information on two volumes, that is, a volume (port  21   d , LU 0 ) and a volume (port  21   d , LU 1 ) (step  702 ). Hereinafter, the server  1   b  successively performs the processing of step  703  and step  100  on the volumes. 
   First, the server  1   b  performs the processing of step  703  on the volume (port  21   d , LU 0 ). Specifically, the server  1   b  acquires a device filename associated with the volume (port  21   d , LU 0 ) from the volume-device file map  1101   b . On the other hand, the server  1   b  reads the configuration definition table  9  from the leading location in the volume (port  21   d , LU 0 ). In this example, the volume (port  21   d , LU 0 ) is realized with the disk device  26   d , as indicated in the volume definition table  8   b  shown in  FIG. 3 . The server  1   b  therefore acquires the configuration definition table  9   a  from the disk drive  26   d.    
   Thereafter, the server  1   b  references the mount destination field  401  of the acquired configuration definition table  9   a  so as to acquire the mount destination directory name /AP/vol1 in the file system of the volume (port  21   d , LU 0 ) that is contained in the record  404   a . Thereafter, the server  1   b  uses the mount destination directory name /AP/vol1 and the acquired device filename /dev/citld1 as arguments to run the volume mount program  18 . The server  1   b  then mounts a volume associated with the device file /dev/cltld1 in the directory /AP/vol1. Likewise, the volume (port  21   d , LU 1 ) is mounted in /DB/vol1. 
   Thereafter, the server  1   b  acquires the environmental variable definition file  15 . In this example, the name of the environmental definition file is env.txt. The server  1   b  therefore checks to see if the name env.txt is specified in the mounted volume. Incidentally, the server  1   b  acquires the environmental variable definition filename from the primary site or a user in advance. The manner of acquisition is identical to the manner of acquiring information on the stored location of the configuration definition information table. In this example, the name env.txt is subordinate to the name /AP/vol1. Therefore, the server  1   b  reads the name env.txt and holds it (step  705 ). In the environmental variable definition file  15 , as mentioned previously, /DB/vol1/db.conf is registered as the value of the DBMS configuration definition filename, and /AP/vol1/ap.conf is registered as the value of the AP configuration definition filename. 
   Finally, the server  1   b  executes the database management system  4   b . At this time, the server  1   b  acquires the DBMS definition information  10  on the basis of the value of the DBMS configuration definition filename registered in the environmental variable definition file  15 , and then initiates the database management system  4   b . Likewise, the server  1   b  acquires the application definition information  13  on the application program  5   b  on the basis of information registered in the environmental variable definition file  15 , and then it initiates the application program  5 . 
   As described above, according to the present embodiment, if a fault occurs in the primary site, the port  21   d  of the storage subsystem  2   b  in the secondary site is connected to the data interface  109   b  of the server  1   b  over the network  3 . The server  1   b  is then started up in order to determine an environment, and the database management system and application are initiated. 
   According to the present invention, there is provided an inexpensive disaster recovery system whose secondary site may have the configuration thereof simplified.