PATENT ABSTRACT
A server has management information including correspondence information between a physical storage region and a virtualized storage region, so as to provide a virtualized storage region. The server includes a unit for using the management information to provide a virtualized storage region to another host and a unit for instructing the control of the storage regions based on the virtualized storage region to a controller for a storage device for providing the physical storage region. Moreover, the controller includes a unit having whole or a part of management information including the correspondence information and performing the control of the storage device based on the virtualized storage region in response to the instruction.

PATENT DESCRIPTION
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a computer system control method, a computer system, and storage device control method and in particular, to a method for controlling information processing system which creates a virtualized volume snapshot, a computer system and storage device control method and a storage device. 
   2. Description of the Related Art 
   In information processing system installed in banks and stock companies, online processing and batch processing may be terminated abnormally by a program bug or storage device failure and any contradictions may occur in data. Moreover, data may be erased by a careless mistake of an operator of an information processing system. To eliminate the data contradiction and resume the processing which has stopped in the middle or to restart the processing which has stopped in the middle, it is often a case that backup operation is performed as a routine work. 
   As a conventional technique of this type, for example, a technique disclosed in JP-A-2000-132343 is known. This conventional technique is related to a storage device system in which to obtain backup for a copy of data without preventing access to the data to be backed up, a frozen image copy (snapshot) with data consistency can be created. In this conventional technique, a snapshot is created not in a host computer but in a storage device system, so as to reduce the load of the host computer accompanied by a snapshot formation such as data copying. In this conventional technique, the storage device system creates a snapshot as follows. Data copying is performed between a copy source (source) volume and a copy destination (destination) volume specified by a host computer and a copy stop for freezing data (division of a volume pair) and data resynchronization are controlled on volume unit basis. Furthermore, in this conventional technique, in order to reduce data copy quantity so as to reduce the time required for copy and the processing load, the data copy, division, resynchronization and the like are performed only for a necessary region within the volume. 
   Use of the aforementioned snapshot is effective not only for the backup but also for the data transfer and the data sharing with data consistency between the databases. 
   Moreover, recently, in the information processing systems, an enormous data quantity is used and there arises a problem that cost for managing a storage device and a storage region has become very high. Concerning this, a research company Moregan Keegan has reported “Virtualizing the SAN” (Jul. 5, 2000). According to this report, a physical volume provided by a storage device is flexibly virtualized according to a request from a host computer, and this virtualized volume is supplied to the host computer, thereby enabling reduction of the management cost. Furthermore, the report shows an example of several system configurations and methods for virtualization. 
   One of them is as follows. A server for virtualization is connected between a host computer and a storage device system and the server address-converts one or more physical volume regions for the host computer, thereby creating a virtualized volume, so as to manage correspondence between a physical volume region and a virtualized volume region. An access to the virtualized volume by the host computer is converted into an access to the physical volume, thereby processing an access request by the host computer. Moreover, in another example, a host computer is connected to a storage device system and further server is connected to the host computer for managing correspondence between a physical volume region and a virtualized volume region. When the host computer accesses the virtualized volume, the request for accessing the virtualized volume by the host computer is received by access processing software on the host computer and the software asks the server about a position of data to be accessed on the physical volume. The server replies the position to the software and the software accesses the physical volume provided by the storage device system by using the position, thereby processing the access request of the host computer. 
   Each of the aforementioned two examples has means for maintaining information of correspondence between a physical volume region and a virtualized volume region and managing correspondence between the physical volume region and the virtual volume region. 
   Moreover, the correspondence between the physical volume and the virtualized volume may be one of the following three cases: a region constituting one virtualized volume is contained in only one physical volume; a region constituting one virtualized volume is contained in a plurality of physical volumes; and regions constituting a plurality of virtualized volumes are contained in only one physical volume. Moreover, a plurality of physical volumes may belong to different storage device systems. 
   In the aforementioned conventional technique in which a storage device system creates a snapshot, management of a source volume and a destination volume and control of data copy, division, resyncrhonization have been performed according to a physical volume provided by the storage device system. For this, when a storage region is virtualized as has been described above, the aforementioned conventional technique has a problem that when creating and using a snapshot according to a virtualized volume used by a host computer, a limit is caused in control of the snapshot. For example, when regions constituting a plurality of virtualized volumes are at least partially contained in one physical volume, in order to create a snapshot of the aforementioned virtualized volume, it becomes necessary to create a snapshot about the aforementioned physical volume. As a result, a destination volume of the physical volume contains both of the virtualized volumes and operation of the snapshot of one of the virtualized volumes may affect the other and it is impossible to perform control such as division and resynchronization for snapshot of each of the virtualized volumes independently from each other. 
   Moreover, when a region constituting one virtualized volume is contained in a plurality of physical volumes, formation of snapshot of the virtualized volume requires formation of snapshot of the plurality of physical volumes. However, since the snapshot formation instruction and control instruction to the storage device system are performed on physical volume basis, snapshot formation for one virtualized volume requires instruction including timing synchronization about the respective physical volumes a plurality of times. This complicates the snapshot management and control, increasing the processing overhead. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide a computer system control method, computer system, and a storage device enabling management and control of processing in a storage device system according to a virtualized storage region in an information processing system performing virtualization of a storage region and in particular, computer system control method, a computer system, and a storage device capable of snapshot formation, management, and control according to a virtualized storage region independently. 
   Moreover, another object of the present invention is to provide a computer system control method, computer system, and a storage device capable of specifying processing, management, and control in a storage device system according to a virtualized storage region in an information processing system performing virtualization of a storage region. 
   According to the present invention, the above object is achieved by a control method for a computer system having at least one storage devices; at least one control device providing at least one storage region of the storage device; and a computer for managing information for providing a virtualized storage region of the storage region; the method including the steps of adding correspondence information between the storage region provided by the storage device and the virtualized storage region, to information for providing the storage region of the computer; holding the correspondence information of the computer entirely or partially in the control device to control the storage device. 
   Furthermore, the above object is achieved by the computer system wherein information in the computer for providing the storage region includes correspondence information between the storage region provided by the storage device and the virtualized storage region, and the control device includes a unit for holding the correspondence information of the computer entirely or partially and controlling the one or more storage devices. 
   Furthermore, the above object is achieved by a storage device control method in the computer system having the steps of adding correspondence information between the storage region provided by the storage device and the virtualized storage region, to information for providing the storage region of the computer; and holding the correspondence information of the computer entirely or partially in the control device to control the storage device. 
   Furthermore, the above object is achieved by a storage device in the computer system wherein the storage device includes a unit for controlling a replica formation of a storage region by an instruction for controlling the replica formation to be performed according to the virtualized storage region, from the control device holding entire or a part of correspondence information between the storage region provided by the storage device and the virtualized storage region. 
   Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing configuration of a computer system according to an embodiment of the present invention. 
       FIG. 2  is a flow chart explaining a first example of processing when a host accesses (read/write) a virtualized volume. 
       FIG. 3  is a flow chart explaining a second example of processing when a host accesses (read/write) a virtualized volume. 
       FIG. 4  is a table explaining an example of virtualized volume information held by a server. 
       FIG. 5  is a table explaining an example of physical volume information held by a server. 
       FIG. 6  is a table explaining an example of mapping information held by a server. 
       FIG. 7  is a table explaining an example of snapshot information held by a server. 
       FIG. 8  is a table explaining an example of in-device physical volume information held by a controller of a storage device. 
       FIG. 9  is a table explaining an example of in-device mapping information held by the controller. 
       FIG. 10  is a flow chart explaining synchronization between the mapping information and the in-device mapping information. 
       FIG. 11  is a table explaining an example of the in-device snapshot held by the controller. 
       FIG. 12  is a flow chart explaining processing of that a storage device forms a physical volume snapshot corresponding to a virtualized volume by indication from the server. 
       FIG. 13  is a continuation of the flow chart of FIG.  12 . 
       FIG. 14  is a continuation of the flow chart of FIG.  12  and FIG.  13 . 
       FIG. 15  is a flow chart explaining processing of that the storage device divides a physical volume pair corresponding to a virtualized volume specified by the server. 
       FIG. 16  is a continuation of the flow chart of FIG.  15 . 
       FIG. 17  is a flow chart explaining an example of performing the division of the physical volume pair by the processing of a step  1407  without a time difference. 
       FIG. 18  is a flow chart explaining a division processing operation of the virtualized volume pair indicating a pair number and a group number. 
       FIG. 19  is a flow chart explaining a processing operation of resynchronization (combination of the pairs). 
       FIG. 20  is a continuation of the flo chart of FIG.  19 . 
       FIG. 21  is a flow chart explaining a processing operation in a case where the virtualized volume is deleted. 
       FIG. 22  is a flow chart explaining a processing operation in a case where the physical volume is not used at all. 
       FIG. 23  is a flow chart explaining a processing operation in a case where the virtualized volume pair is deleted. 
       FIG. 24  is a flow chart explaining a processing operation by which a backup is obtained. 
       FIG. 25  shows another example of physical volume information in the device. 
       FIG. 26  shows another example of snapshot information in the device. 
       FIG. 27  is a block diagram showing the constitution of the computer system according to another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   Description will now be directed to a computer system control method, a computer system, and a storage device according to embodiments of the present invention with reference to the attached drawings. 
     FIG. 1  is a block diagram showing configuration of a computer system according to an embodiment of the present invention. In  FIG. 1 , there are shown a server  100 , virtualized volume information  101 , physical volume information  102 , mapping information  103 , snapshot information  104 , a host  200 , application software  210 , OS  220 , access processing software  230 , a storage device  300 , a controller  310 , in-device physical volume information  310 , in-device mapping information  312 , in-device snapshot information  313 , difference information  314 , a physical volume  400 , a backup storage device  500 , a storage area network (SAN)  600 , a network  700 , and a management terminal  800 . 
   The computer system according to the embodiment of the present invention includes: the server  100 , the host  200 , the storage device  300 , the backup storage device  500 , and the management terminal  800 . The server  100 , the host  200 , the storage device  300 , the backup storage device  500 , and the management terminal  800  are connected one to another via a network  700 . As a protocol and standard used in the network  700 , there can be exemplified IP. Moreover, the server  100 , the host  200 , the storage device  300 , the backup storage device  500 , and the management terminal  800  are also connected one to another via storage area network (SAN)  600  serving as a path for data transfer. As a protocol and standard used in the SAN, there can be exemplified a fibre channel (FC), IP, Infini Band, and the like. 
   The host  200  contains application software  210 , OS  220 , and access processing software  230 . The application software  210 , for example, may be a backup software. Here, the application software  210  also contains a middle-ware such as database management software (DBMS). The access processing software  230  may be a file system, a device driver, and the like. 
   The storage device  300  has a function for recording/reproducing data used by the host  200  according to a request from the server  100  or the host  200 . The storage device  300  may be a single magnetic disc, a composite magnetic disc device (JBOD, Just Bunch OF Disks), a magnetic disc of RAID (Redundant Arrays of Inexpensive Disks) configuration having a controller. The storage device  300  has the controller  310  for performing processing which will be detailed later. The storage device  300  provides the physical volume  400  as a data storage region to the server  100  or to the host  200 . 
   The backup storage device  500  is a storage device for storing backup of the data stored in the storage device  300  and may be a tape device, a tape library device, a magnetic disc device, a magneto-optical disc device, and the like. 
   Each of the server  100 , the host  200 , the controller  310 , and the management terminal  800  has components indispensable to a computer such as a memory and a CPU for executing processing but they are not depicted because they are not important in the embodiment of the present invention. 
   Processing according to the embodiment of the present invention which will be explained below is performed as follows. In an environment that the physical volume  400  provided by the storage device  300  is virtualized by the server  100  and supplied to the host  200 , according to an instruction from the server  100 , the storage device  300  forms a snapshot of the physical volume corresponding to the volume virtualized by the storage device  300  and controls the division and the resynchronization. 
   FIG.  2  and  FIG. 3  show a flow chart for explaining a processing operation when the host  200  accesses (read/write) the virtualized volume. Hereinafter, explanation will be given on this. Firstly, a first example will be explained with reference to FIG.  2 . 
   (1) The application software  210  on the host  200  specifies a virtualized volume and access range of the virtualized volume and transmits an access request to the OS  220  (step  1001 ). 
   (2) The OS  220  which has received the access request accesses a virtualized volume provided by the server  100  via the SAN  600  (step  1002 ). 
   (3) The server  100  accessed, uses an access parameter and virtualized volume information  101  (which will be detailed later) to identify a virtualized volume to be accessed and by using mapping information  103  (which will be detailed later) specifies a region of the physical volume  400  corresponding to the access range (steps  1003  and  1004 ). 
   (4) Moreover, the server  100  uses physical volume information  102  (which will be detailed later) to identify an address of the physical volume  400  on the SAN  600  and accesses a target region of the physical volume  400  via the SAN  600  and reports an access result to the OS  220  of the host  200  (steps  1005  to  1007 ). 
   (5) The OS  220  reports the access result to the application software  210  which has requested the access and terminates the processing (step  1008 ). 
   In the aforementioned processes, upon access, read data or write data is transferred between the host  200  and the server  100 , and between the server  100  and the storage device  300  via the SAN  600 . 
   Next, referring to the flow chart of  FIG. 3 , explanation will be given on a second example of processing operation performed when the host  200  accesses (read/write) the virtualized volume. 
   (1) The application software  210  on the host  200  specifies a virtualized volume and an access range of the virtualized volume and transmits an access request to the OS  220  (step  1101 ). 
   (2) The OS  220  which has received the access request requests an access to the access processing software  230  (step  1102 ). 
   (3) Upon reception of the access request in step  1102 , the access processing software  230  asks the server  100  about a physical position of the access range via the network  700  or the SAN  600  (step  1103 ). 
   (4) The server  100  which has received the query identifies a virtualized volume by using an access parameter and virtualized volume information  101  (which will be detailed later) and identifies a region of the physical volume corresponding to the access range by using mapping information  103  (which will be detailed later) (steps  1104  and  1105 ). 
   (5) Moreover, by using physical volume information  102  (which will be detailed later), the server  101  identifies an address of the physical volume  400  on the SAN  600  and replies to the access processing software  230  (steps  1106  and  1107 ). 
   (6) By using the replied physical volume address and region, the access processing software  230  accesses the target region of the physical volume  400  via the SAN  600  and reports an access result to the OS  220  (steps  1108  and  1109 ). 
   (7) The OS  220  reports an access result to the application software  210  which has requested access and terminates the processing (step  1110 ). 
   In the aforementioned processing, read data or write data is transferred between the host  200  and the storage device  300  via the SAN  600 . 
   By the aforementioned processing, the server  100  can virtualize the physical volume  400  provided by the storage device  300  and provide the virtualized volume to the host  200  and the host  200  can store data in the virtualized volume and access the virtualized volume. 
   In the aforementioned processing examples, the application software  210  specifies a virtualized volume and an access range of the virtualized volume. However, it is also possible that the application software  210  specifies a file name to be accessed, and the OS  220  or the access processing software  230  determines a range on the virtualized volume from the file name and accesses it. 
     FIG. 4  explains an example of the virtualized volume information  101  held by the server  100 . Next, explanation will be given on this virtualized volume information  101 . The virtualized volume  101  is composed of a virtualized volume number which identifies a virtualized volume currently provided by the server  100 ; and a SAN address indicating an address of the virtualized volume on the SAN  600 . The SAN address may be, for example, information identifying the volume on FC, IP, iSCSI protocol such as WWN, LUN, IP address, MAC address. 
     FIG. 5  is a table explaining an example of the physical volume information  102  held by the server  100 . Next, explanation will be given on the physical volume information  102 . The physical volume information  102  is composed of a device number, a physical volume number, a SAN address, a vendor name, a type name, a production number, a version number, and a state. 
   In the aforementioned, the device number is a number indicating a storage device  300  which can be used by the server  100 . The physical number indicates the physical volume  400  which is provided by the storage device  300  and can be used by the server  100 . The SAN address indicates an address of the physical volume  400  in the SAN  600 . The vendor name indicates a vendor name of the storage device  300 . The type name indicates a type of the storage device  300 . The production number indicates a production number of the storage device  300 . The version number indicates a version in the type of the storage device. The state indicates a state of the physical volume  400 . 
   As a method for the server  100  to fetch the aforementioned information from the storage device  300  may be issuing an SCSI INQUIRY command and a MODE SENSE command. In this embodiment, the storage device  300  may be only one or a plurality storage devices  300  may exist and in the latter case, the storage devices  300  may be of different vendor types and different versions. 
     FIG. 6  is a table showing an example of the mapping information  103  held by the server. Next, explanation will be given on this mapping information  103 . The mapping information  103  is composed of a virtualized volume number, virtualized volume size, a number of physical volumes (physical volume count), a concatenation order, a device number, a physical volume number, a physical volume range, and snapshot attribute. 
   In the aforementioned, the virtualized volume number is a number indicating a virtualized volume currently provided by the server  100  and corresponds to the virtualized volume number of the virtualized volume information  101 . The virtualized volume size indicates a size of the virtualized volume. The number of physical volumes shows number of regions of the physical volume  400  constituting a virtualized volume. The physical volume number shows a physical volume  400  where the aforementioned region exists and corresponds to the physical volume number of the physical volume information  102 . The device number indicates the storage device  300  where the physical volume  400  exists and corresponds to the device number of the physical volume information  102 . The physical volume range indicates a range of the aforementioned region on the physical volumes  400 . The snapshot attribute indicates whether the virtualized volume is related to the snapshot or not and indicates an attribute when related and may be a pair number (which will be detailed later) and may indicate whether the virtualized volume is a destination or a source. The concatenation order is a number starting from 1 and incremented by one when the region of the physical volume  400  constitutes the virtualized volume. The regions of the physical volumes  400  are concatenated according to the concatenation order, thereby constituting the aforementioned virtualized volume. 
     FIG. 7  is a table showing an example of the snapshot information  104  held by the server  100 . Next, explanation will be given on this snapshot information  104 . The snapshot information  104  is composed of a pair number, a group number, a source volume, a destination, and a state. 
   In the aforementioned, the pair number indicates a pair (virtualized volume pair) of a destination virtualized volume and a source virtualized volume of the snapshot managed by the server  100 . The group number indicates a group to which the virtualized volume pair belongs. The source volume indicates a virtualized volume number of the source virtualized volume. The destination volume indicates a virtualized volume number of the destination virtualized volume. The state indicates a state of the virtualized volume pair: “being formed”, “formation complete”, “being divided”, or “division complete” as will be detailed later. 
   Explanation has been given on the information held by the server  100 . Next, explanation will be given on the information held by the controller  310  of the storage device  300 . The in-device mapping information  312  is information synchronized with the mapping information  103 . 
     FIG. 8  is a table showing an example of the in-device physical volume information  311  held by the controller  310  of the storage device  300 . Next, explanation will be given on this in-device physical volume information  311 . The in-device physical volume information  311  is composed of information items: a physical volume number, a SAN address, and state. 
   In the aforementioned, the physical volume number indicates the physical volume  400  which can be provided by the storage device  300 . The SAN address indicates an address of the physical volume  400  in the SAN  600 . The state indicates the state of the physical volume  400  such as “in use”, “unused”, “access prohibited”, and “failed”. The “in use” indicates that the data used by the host  200  is stored and can be accessed from the server  100  or the host  200 . The “unused” indicates that no data is stored to be used by the host  200  and can be assigned as a destination volume. The “access prohibited” indicates that the volume is used as a destination volume but cannot be accessed from the server  100  or the host  200 . For example, a destination volume whose division is not complete is in the “access prohibited” state. The operation of division will be detailed later. The “failed” indicates that the volume has an error and cannot be used. The controller  310  can extract a physical volume which can be allocated as a destination volume by using the state information. For performing this extraction at a high speed, it is possible to employ a list structure. 
     FIG. 9  is a table showing an example of the in-device mapping information  312  held by the controller  310 .  FIG. 10  is a flow chart showing synchronization processing between the mapping information  103  and the in-device mapping information  312 . Next, explanation will be given on this in-device mapping information  312  and its formation. The in-device mapping information  312  is composed of a virtualized volume number, a number of physical volumes, a concatenation order, a physical volume number, a physical volume range, and a snapshot attribute. The in-device mapping information  312  is created according to the flow of  FIG. 10 , for example, when initializing the information processing system according to the embodiment of the present invention. Next, explanation will be given on the processing of FIG.  10 . 
   Firstly, the server  100  checks the mapping information  103  and extracts mapping of a virtualized volume relating to the physical volume  400  for the respective storage devices  300  (step  1201 ) and reports it to the storage devices  300  (step  1202 ). Upon reception of this report, the storage device  300  creates in-device mapping information  312  according to the report (step  1203 ). For example, when the configuration of the virtualized volume provided by the server  100  has been modified and the mapping information is modified, the server  100  and the storage device  300  perform a processing identical to the aforementioned, and the storage device  300  updates the in-device mapping information  312  for synchronization of the information. The virtualized volume number, the concatenation order, the physical volume number, the physical volume range, and the snapshot attribute of the in-device mapping information  312  correspond to the respective items of the mapping information  103 . However, the physical volume number and the physical volume range of the in-device mapping information  312  include only those existing in the storage device  300  and even when the physical volume  400  constituting one virtual volume exists in a plurality of storage devices  300 , the other storage devices are not contained and the concatenation order may be jumping values. The number of the physical volumes indicates the aforementioned physical volume number and the physical volume range and does not contain the other storage device  300 . 
     FIG. 11  is a table showing an example of the in-device snapshot  313  held by the controller  310 . Next, explanation will be given on this in-device snapshot information  313 . The in-device snapshot information  313  is composed of a pair number, a group number, a source volume, a destination volume, a number of physical volume pairs (physical volume pair count) a source physical volume number, a destination physical volume number, and a state. 
   In the aforementioned, the pair number indicates a virtualized volume pair of the snapshot managed by the server  100  and the group number indicates a group (which will be detailed later) to which the virtualized volume pair belongs and they correspond to the pair number and the group number of the snapshot information  104 . The source volume indicates a virtualized volume number of the source virtualized volume. The destination volume indicates a virtualized volume number of the destination virtualized volume. The source physical volume number indicates a physical volume number of the physical volume  400  having a region constituting the source virtualized volume. The destination physical volume number indicates a physical volume number of the destination physical volume  400 . 
   In the embodiment of the present invention, the storage device  300  has the snapshot formation function on volume basis of the physical volume  400  and a virtualized volume snapshot formation is realized through that the storage device  300  creates a snapshot of the physical volume  400  constituting the virtualized volume. When a plurality of physical volumes are present to constitute the aforementioned virtualized volume, a plurality of pairs of physical volumes  400  (physical volume pair) are set. That is, there are the number of source physical volumes and the number of the destination physical volumes identical to the aforementioned number. The number of the physical volume pairs indicates the number of physical volume pairs. The state indicates a state of the virtualized volume pair corresponding to the snapshot information  104 . 
     FIG. 12 ,  FIG. 13 , and  FIG. 14  show a continuous flow chart for creating a snapshot of the physical volume  400  corresponding to the virtualized volume by the storage device  300  according to an instruction from the server  100 . Next, explanation will be given on the snapshot forming processing with reference to the flow chart. 
   (1) Upon reception of a snapshot forming request for a virtualized volume (source virtualized volume) from the host  200  or the management terminal  800 , the server  100 , by using the virtualized volume information  101 , selects a unused virtualized volume number as a destination virtualized volume number and by using the mapping information  103 , specifies a storage device  300  having the physical volume  400  constituting the source virtualized volume. The storage device  300  may be only one or there may be more than one (step  1301 ,  1302 ). 
   (2) Next, by using the snapshot information  104 , the server  100  selects a unused pair number and determines a group number of the virtualized volume pair according to a snapshot forming request condition (which will be detailed later) and specifies a virtualized volume number of the source virtualized volume (source virtualized volume number), the aforementioned destination virtualized volume number, the aforementioned pair number, and the aforementioned group number and requests a snapshot formation to the controller  310  of the storage devices  300  via the network  700  or the SAN  600  (steps  1303  to  1305 ). 
   (3) Moreover, the server  100  adds a new entry to the snapshot information and sets the aforementioned values in the pair number, the group number, the source virtualized volume number, and the destination virtualized volume number, and sets the state to “being formed” (step  1306 ). 
   Here, explanation will be given on the group. The group is a set of the aforementioned virtualized volume pairs and each pair belongs to one of the groups. Because of the reason which will be detailed later, pairs belonging to different groups are assured to be divided and combined at independent timings. Pairs belonging to the same group are not assured to be divided and combined at independent timings. Accordingly, an identical group number is set when the division and combination for the pairs are performed at overlapped timing and when it is clear that the division and combination for the pairs are performed at the same timing. 
   (4) Returning back to the explanation of  FIG. 12 , the controller which has received the aforementioned request adds a new entry to the in-device snapshot information  313  and sets the values received in the aforementioned request, in the pair number, the group number, the source virtualized volume number, and the destination virtualized volume number and sets the state to “being formed” (step  1307 ). 
   (5) Furthermore, by using the in-device mapping information  312 , the controller  310  identifies the number of physical volumes  400  (source physical volumes) in the storage device  300  constituting the specified source virtualized volume and the physical volume numbers of the physical volumes  400  and sets the numbers in the numbers of physical volume pairs in the in-device snapshot information  313  (steps  1308  and  1309 ). 
   (6) Furthermore, by using the in-device snapshot Information  313 , the controller  310  checks whether any other source virtualized volume composed of the aforementioned source physical volume exists (step  1310 ). 
   (7) When the check in  1310  results in that no other virtualized volume exists, a destination physical volume is not yet set in the source physical volume and accordingly, the controller  310  selects a unused physical volume  400  by using the in-device physical volume information  311  and sets the state to “access prohibited” so as not to be accessed from the server  100  or the host  200 . The controller  310  assigns a SAN address which can be allocated and is unused (steps  1311 ,  1312 ). 
   (8) When the check in  1310  results in that another virtualized volume does exist, a destination physical volume has been set in the source physical volume and accordingly, the controller  310  checks the group number of this virtualized volume pair by using the in-device snapshot information  313 . When this check results in that the group number is identical to the group number specified by the server  100 , the destination physical volume already set can be set as a destination physical volume of the snapshot requested (steps  1313  and  1314 ). 
   (9) When the check of step  1313  results in that the group number is different from the group number specified, a unused physical volume  400  is selected by using the in-device physical volume information  311 , and the state is set to “access prohibited” so as not to be accessed from the server  100  or the host  200  and a SAN address which can be allocated and is unused is assigned (steps  1315  and  1316 ). 
   (10) After the processes of steps  1314  and  1316  or after the process of step  1312 , the controller  310  sets the source physical volume number identified in the process of step  1308 , in the source physical volume number of the in-device snapshot information  313 , and sets the selected destination physical volume number on the destination physical volume number. That is, the aforementioned source physical volume and the destination physical volume become a physical volume pair (steps  1317  and  1318 ). 
   (11) The source physical volume identified in step  1318  may be one or more. When a plurality of source physical volumes are present, the controller  310  checks whether all the pairs have been set for the identified origination physical volumes. And if there is any pair not set, the processing from  1310  is repeated for the remaining source volume. The aforementioned processing is performed for all to determine destination physical volumes and to set the source physical volume numbers and the destination physical volume numbers of the in-device snapshot information  313  (steps  1319  and  1320 ). 
   (12) Next, by using the method and processing as disclosed in JP-A-2000-132343 for example, the controller  310  forms a snapshot by copying data with the physical volume pair which has been set in the in-device snapshot information  313 . That is, the controller  310  has a bit map (difference information  314 ) indicating a difference between the volume regions of the physical volume pair prior to the snapshot formation and data copy is performed from the source to the destination for the region where the difference exists according to the difference information  314 . The difference information  314  is turned off for the region whose copy is complete. Moreover, as shown in the aforementioned Publication, two types of the difference information  314  can be held to distinguish management of updating before and after the division. When the destination physical volume is already set for the source physical volume in step  1315  and the controller  310  has selected a new unused physical volume as the other destination physical volume, i.e., when the controller  310  has set a plurality of destination physical volumes for one source physical volume, a plurality of physical volume pairs exist for one source physical volume and the controller  310  forms a snapshot for each of the plurality of pairs. In this case, the controller has plurality of difference information  314  of the plurality of pairs and performs the aforementioned data copy (step  1321 ). 
   (13) The controller  310  checks whether snapshot formation is complete for all the pairs of the physical volumes  400  set in the in-device snapshot information  313 . If complete, the controller  310  updates the snapshot state requested in the in-device snapshot information  313  to “formation completes” (steps  1322  and  1323 ). 
   (14) Next, the controller  310  adds a new entry to the in-device mapping information  312  and specifies how the destination virtualized volume is configured by the destination physical volume. That is, the controller  310  sets the aforementioned destination virtualized volume number in the virtualized volume number, sets the aforementioned number of the physical volumes in the physical volume count, sets the aforementioned destination physical volume number in the physical volume number, and sets the aforementioned pair number and the destination in the snapshot attribute. Moreover, the controller  310  sets as the concatenation order, the concatenation order of the source physical volume forming a pair with the aforementioned destination physical volume and sets as the physical volume range, the physical volume range of the aforementioned source physical volume. The concatenation order and the physical volume range are fetched from the source virtualized volume of the mapping information  312  (step  1324 ). 
   (15) Next, the controller  310  reports completion of the requested snapshot formation to the server  100  via the network  700  or the SAN  600 . Here, the controller  310  reports an updated portion of the in-device mapping information  312 : the configuration of the destination virtualized volume set in step  1324  by the aforementioned destination physical volume; the physical volume number set to “access prohibited” in steps  1312  and  1316 ; and its SAN address (step  1325 ). 
   (16) The server  100  which has received the report and notification adds to the physical volume information  102 , an entry for the physical volume whose state has become “access prohibited”; sets the device number of the storage device  300 ; sets the physical volume number and the SAN address according to the aforementioned notification; sets the state to “access prohibited”; fetches and sets the remaining items from the storage device  300  by using the SCSI INQUIRY command, the MODE SENSE command, and the like (step  1326 ). 
   (17) Furthermore, the server confirms reception of the report of the aforementioned snapshot formation completion, the mapping information and the physical volume information from all the storage devices  300  having the physical volumes  400  constituting the aforementioned source virtualized volume which has been identified in step  1302  and has requested the snapshot formation in step  1305 . If all of them have been received, the server  100  sets the state in the entry of the aforementioned pair number in the snapshot information  104  to “formation complete” and adds a new entry to the mapping information  103 . Moreover, according to the notification contents, the server  100  sets the virtualized volume number of the destination virtualized volume in the virtualized volume number and accumulates the physical volume range size of the destination physical volume in the virtualized volume size. Moreover, the server  100  accumulates the number of the destination physical volume in the physical volume count and further sets the concatenation order, the device number, the physical volume number, the physical volume range, and the snapshot attribute from the aforementioned notification contents and device number of the storage device  300  which has performed the notification. That is, by using the notification contents from the controller  310  of the storage device  300 , the server  100  reflects the update of the in-device mapping information  312  held by the controller  310 , on the mapping information  103  so as to synchronize between the information items (steps  1237  to  1239 ). 
   (18) Next, compares information related to the source virtualized volume to information related to the destination virtualized volume in the mapping information  103  and confirms that the virtualized volume size is matched and the number of physical volumes is matched. Furthermore, the server  100  confirms that the physical volume concatenation order is continuous without jumping (skipping) ( 1330 ). 
   (19) Next, the server  100  reports the snapshot completion to the host  200  or to the management terminal  800  and terminates the processing (step  1331 ). 
   As has been described above, according to the instruction from the server  100 , the storage device  300  forms a snapshot of the physical volume  400  corresponding to the virtualized volume. Accordingly, the server  100  can prepare for fetching the snapshot of the virtualized volume by one instruction to the storage device  300  without causing a load to the server  100  such as data copy. 
   Moreover, in the aforementioned processing, by using the notification contents from the controller  310  of the storage device  300 , the server  100  reflects update of the in-device mapping information  312  held by the controller  310  on the mapping information so as to synchronizing between the information items. Accordingly, the server  100  can always recognize the physical volume  400  constituting the destination virtualized volume in spite of the new allocation/play-and-plug operation of the physical volume  400  constituting the destination virtualized volume. For example, when a source physical volume and a destination physical volume have identical contents, the server  100  can prevent the problems such as incorrect storage management or processing failure (in recognition of the source physical volume and the destination physical volume). 
   FIG.  15  and  FIG. 16  are a continuous flow chart showing a division processing according to an instruction of the server  100  with a virtualized volume specified, for dividing a pair of the physical volumes  400  corresponding to the virtualized volume. 
   (1) Upon reception of a pair division request related to a virtualized volume from the host  200  or the management terminal  800 , the server  100 , by using the mapping information  103 , identifies a storage device  300  having the physical volume constituting the virtualized volume, specifies the virtualized volume number in the controller  310  of the storage device  300 , and requests a pair division related to the virtualized volume via the network  700  or the SAN  600 . The storage device  300  may be one or there are more than one storage devices  300 . Moreover, the server  100  identifies a virtualized volume pair in which the virtualized volume in the snapshot information  104  is a destination or source and sets the state to “being divided” (steps  1401  to  1403 ). 
   (2) Upon reception of the aforementioned request, the controller  310 , by using the in-device snapshot information  313 , Identifies a virtualized volume pair number which the virtualized volume is a source or destination and sets the state in the entry of the pair number to “being divided”. The aforementioned pair number may be only one or there may be more than one. Next, the controller  310  identifies a physical volume in the entry of the pair number in the in-device snapshot information  313  (steps  1404  to  1406 ). 
   (3) Next, the controller  310  divides the physical volume according to the method and processing as disclosed, for example, in JP-A-2000-132343. That is, the controller  310  has a bit map (difference information  314 ) as information for the physical volume pair indicating a difference between the volume ranges from the snapshot formation and to the division. Referencing the difference information  314 , the controller  310  performs data copying from the source to the destination where a difference is present and turns the difference information off for the region whose copying is complete. When there are a plurality of physical volume pairs for one or more virtualized volume pairs, the pair divisions are all performed without a time difference. This processing of the pair divisions without a time difference will be detailed later (step  1407 ). 
   (4) After confirming that the physical volume division is completed by the processing of step  1407 , the controller  310  sets the state in the entry of the destination physical volume of the aforementioned physical volume pair to “in use” and allows access to the physical volume (steps  1408  and  1409 ). 
   (5) The controller  310  checks whether division is complete for all the physical volume pairs existing in the entry in the in-device snapshot information  313 . If not complete, the controller continues the processing from step  1408 . If the division is complete for all the physical volume pairs existing in the entry in the in-device snapshot information  313 , the controller sets the state in the entry to “division complete” (steps  1410  and  1411 ). 
   (6) Furthermore, the controller  310  checks whether division is complete for all the entries in the in-device snapshot information  313 . If No, the controller  310  continues the processing from step  1408 . If division is complete for all the entries in the in-device snapshot information  313 , the controller  310  reports completion of the requested division to the server  100  via the network  700  or the SAN  600  and notifies the physical volume number whose state is set to “in use” in step  1408  (steps  1412  and  1413 ). 
   (7) Upon reception of the report and notification in the processing of step  1413 , the server  100 , according to the report contents and the device number of the storage device  300 , sets the state in the entry of the physical volume in the physical volume information  102  to “in use” (step  1414 ). 
   (8) Furthermore, the server  100  checks whether the division completion report and notification have been received from all the storage devices  300  which were identified in the processing of step  1401  and requested virtualized volume pair division in the processing of step  1402 . After this confirmation, the server  100  sets the state in the entry of the pair number in the snapshot information  104  to “division complete” and reports the division completion to the host  200  or the management terminal  800 , thereby terminating the processing (steps  1415  to  1417 ). 
     FIG. 17  is a flow chart showing an example of physical volume pair division by the processing of step  1407  without a time difference. Next, explanation will be given on this. 
   The controller  310  simultaneously holds acceptance of write from the server  100  or the host  200  for a source physical volume of the respective physical volume pairs (step  1501 ) and saves the aforementioned difference information  314  for all the pairs (step  1502 ), so that update from the division to the resynchronization is recorded in another difference information  314  (step  1503 ). The controller  310  resumes write acceptance (step  1504 ) and performs data copying by referencing the difference information  314  which has been saved (step  1505 ). 
   As has been described above, since the division of a physical volume pair can be performed only by saving the difference information  314 , it is possible to reduce the write acceptance hold time. 
   In the processing explained with reference to  FIG. 15  to  FIG. 17 , a virtualized volume specified by the host or the management terminal  800  may be a source or a destination of a pair. However, the processing may be performed only for either of the source or the destination. Moreover, in the aforementioned, explanation has been given on a pair division with specification of a virtualized volume. However, the pair division processing can also be performed by specifying a pair number or a group number. 
     FIG. 18  is a flow chart showing a division processing with specification of a pair number or a group number. Next, explanation will be given on this case. 
   (1) Upon reception of a division request of a virtualized volume pair with specification of a pair number or a group number from the host  200  or the management terminal  800 , the server  100 , by using the snapshot information  104 , identifies a pair having the specified pair number or the group number and source virtualized volume of the pair ( 1601 ); and by using the mapping information  103 , the server  100  identifies a storage device  300  having the physical volume constituting the source virtualized volume (steps  1601  and  1602 ). 
   (2) The server  100  requests division of the virtualized volume pair via the network  700  or the SAN  600  with specifying the pair number or the group number in the controller  310  of the storage device  300 . The storage device  300  may be realized by one or more storage devices  300 . Moreover, the server  100  sets the state in the entry of the pair in the snapshot information  104  to “being divided” (steps  1603  and  1604 ). 
   (3) Upon reception of the request from the server  100  in step  1603 , the controller  310 , by using the in-device snapshot information  313 , identifies an entry whose pair number and group number are matched with the aforementioned specification, and sets the state in the entry to “being divided”. In this specification, when a pair number is specified, the entry is one but when a group number is specified, the entry may be only one or there may be more than one entry (steps  1605  and  1606 ). 
   (4) Next, the controller  310  identifies a physical volume pair of the entry. Independently of the number of the entries, the physical volume pair may be only one or there may be a plurality of physical volume pairs. The controller  310  executes the processes of steps  1407  to  1413  explained with reference to FIG.  15  and FIG.  16 . When there are a plurality of physical volume pairs, the controller  310  executes division of the pairs without a time difference (steps  1607  and  1608 ). 
   (5) Upon reception of the report that the division is complete and notification of the physical volume which has become “in use”, the server  100  sets the state in the entry of the physical volume in the physical volume information  202  to “in use” according to the notification content and the device number of the storage device  300  (step  1609 ). 
   (6) Furthermore, the server  100  confirms that the division complete report and notification have been received from all the storage devices  300  which have been identified in step  1602  and requested the virtualized volume pair division in step  1603 . After the confirmation, the server  100  sets the state in the entry in the snapshot information  104  to “division complete” and reports the division complete to the host  200  or the management terminal  800  (steps  1610  to  1612 ). 
   As has been described above, the storage device  300  executes division of the physical volume pair corresponding to the virtualized pair by an instruction from the server  100 . Even when a plurality of virtualized volume pairs are specified by specifying a virtualized volume or a group instead of the pair number, the server  100  can realize the virtualized volume pair division by only one instruction to the respective storage devices  300 . 
   Moreover, when the virtualized volume pair division is accompanied by division of a plurality of physical volume pairs, the division of the plurality of physical volume pairs can be performed without a time difference. Thus, for a virtualized volume or its group to be divided, a pair can be divided by the storage device  300  while maintaining data matching and a snapshot can be obtained. 
   FIG.  19  and  FIG. 20  are a continuous flow chart showing processing of resynchronization (pair combination). Next, referring to the flow chart of FIG.  19  and  FIG. 20 , explanation will be given on resynchronization. That is, according to an instruction by the server  100  with specifying a virtualized volume, the storage device  300  resynchronizes (combines the pair) data to be stored in the source physical volume and in the destination physical volume for the physical volume  400  corresponding to the virtualized volume, thereby resynchronizing stored data of a virtualized volume pair related to the aforementioned virtualized volume. Explanation will be given on this processing. 
   (1) Upon reception of a pair combination request related to a virtualized volume from the host  200  or the management terminal  800 , the server  100 , using the mapping information  103 , identifies a storage device  300  having the physical volume constituting the aforementioned virtualized volume and requests a pair combination related to the virtualized volume via the network  700  or the SAN  600  with specifying the virtualized volume number in the controller  310  of the storage device  300 . The storage device  300  may be only one or there may be a plurality of the storage devices  300  (steps  1701  and  1702 ). 
   (2) Moreover, the server  100  identifies a pair whose virtualized volume is a destination or a source in the snapshot information  104  and sets the state to “being formed” (step  1703 ). 
   (3) Upon reception of a request in step  1702 , the controller  310 , by using the in-device snapshot information  313 , identifies a pair number of a virtualized volume pair in which the aforementioned virtualized volume is a source or a destination virtualized volume and sets the state in the entry of the pair number to “being formed”. The pair number may be only one or there may be a plurality of pair numbers (steps  1704  and  1705 ). 
   (4) Next, the controller  310  identifies a physical volume pair of the entry of the pair number in the in-device snapshot information  313  and identifies a destination physical volume of the aforementioned volume pair (steps  1706  and  1707 ). 
   (5) Next, the controller  310  prohibits access to the aforementioned destination physical volume from the server  100  or the host  200  and sets the state in the entry for the aforementioned destination physical volume in the in-device physical volume information  311  to “access prohibited” (step  1708 ). 
   (6) Next, according to the method and processing disclosed in JP-A-2000-132343, the controller  310  executes combination of the aforementioned physical volume pair. That is, the controller  310  has a bit map (difference information  314 ) indicating a difference between the volume regions from the division to the combination of the physical volume pair. Referencing the difference information  314 , the controller  310  performs data copy from a source to a destination for the regions where a difference is present and turns off the difference information  314  where the copying is complete (step  1709 ). 
   (7) The controller confirms that combination is complete for all the physical volume pairs existing in the aforementioned entry in the in-device snapshot information  313 . After this confirmation, the controller  310  sets the aforementioned state in the entry to “formation complete” (steps  1710  and  1711 ). 
   (8) Furthermore, the controller  310  checks whether combination is complete for all the entries in the in-device snapshot information  313 . If not complete, the controller  310  again executes the processing from the step  1710 . When the combination is complete for all aforementioned entries, the controller  310  reports completion of the requested combination via the network  700  or the SAN  600  and notifies the physical volume number which has been set to “access prohibited” in the process of step  1708  (steps  1712  and  1713 ). 
   (9) Upon reception of the report and notification in the process of step  1713 , according to the notification content and the device number of the storage device  300 , the server  100  sets the state in the entry of the physical volume in the physical volume information  102  to “access prohibited” (step  1714 ). 
   (10) Furthermore, the server  100  confirms that the aforementioned combination complete report and notification have been received from all the storage devices  300  which have been identified in step  1701  and have requested a virtualized volume pair combination in step  1702 . After this confirmation, the server  100  sets the state in the entry of the pair number in the snapshot information  104  to “formation complete” and reports the completion of combination to the host  200  or to the management terminal  800 , thereby terminating the processing (steps  1715  to  1717 ). 
   In the aforementioned processing, the virtualized volume specified by the host  200  may be a source or may be a destination in the pair. That is, both cases can be processed. However, it is also possible to process only one of the cases. 
   Moreover, explanation has been given on a pair combination with specifying of a virtualized volume. A pair combination with specifying of a pair number or a group number can also be processed like in the pair division processing by replacing the “division”, “being divided”, “in use”, and “division complete” in the pair division processing of steps  1601  to  1612  in the flow chart of  FIG. 18  with “combination”, “being formed”, “access prohibited” and “formation complete”. 
   As has been described above, the storage device  300  performs combination of a physical volume pair corresponding to a virtualized volume pair according to an instruction of the server  100 , so that not only with specifying the pair number but also with specifying a virtualized volume and a group where a plurality of virtualized volume pairs may be present, the server  100  can realize a virtualized volume pair with one instruction to the respective storage devices  300 . 
   By performing the aforementioned snapshot formation processing, in a plurality of virtualized volume pairs having different group numbers, even when the source physical volume is identical, the source physical volume can be handled as different volumes, i.e., the physical volume pairs are different. This enables the aforementioned division and combination for the respective virtualized volume pairs at independent timings. That is, division and combination of one of the virtualized volume pairs need not be affected by the other virtualized volume pair. 
   In the aforementioned, when different numbers are assigned for all the virtualized volume groups, it is necessary to prepare separate destination physical volumes for the respective virtualized volume pairs and there may arise shortage of the physical volume  400  of the storage device  300 . To prevent this, an identical group number can be assigned for virtualized volume pairs which are divided and combined at the same timing. 
   As an example of performing division or combination at the same timing, there is a case when a plurality of data items used by the host  200  are dispersed in a plurality of virtualized volumes and snapshot of the aforementioned virtualized volumes is used for backup of the data items and data sharing/passing between databases. There is also a case when data, Index, log used by DBMS on the host  200  are dispersed in a plurality of virtualized volumes and snapshot is simultaneously used for backup. Moreover, for virtualized volume pairs whose division and combination will not be overlapped, it is possible to assign an identical group number. Moreover, it is possible to prepare a particular group number (such as 0) to be assigned for a virtualized volume pair whose division and combination need not be performed at an arbitrary timing. 
   In the aforementioned example, the group number is indicated by a numeric and processing is performed referencing the numeric. However, it is also possible to show such information as a bit map. For example, if a certain bit is ON, it means that division or combination need not be performed at an arbitrary timing. 
     FIG. 21  is a flow chart showing a processing operation for deleting a virtualized volume. Next, explanation will be given on this. 
   (1) Firstly, by using the mapping information  103 , the server  100  identifies a storage device  300  of an entry of the aforementioned virtualized volume and deletes the entry of the virtualized volume in the virtualized volume information  101  and the mapping information  103  (steps  1801  and  1802 ). 
   (2) Next, the server  100  notifies deletion of the virtualized volume to the controller  310  of the aforementioned storage device  300  (step  1803 ). 
   (3) Upon reception of the notification of the virtualized volume deletion, the controller  310  deletes the entry in the in-device mapping information  312  and synchronizes information between the server  100  and the controller  310 , thereby terminating the processing. However, in the mapping information  103 , when the aforementioned virtualized volume is a destination or a source, it is impossible to delete the entry (step  1804 ). 
     FIG. 22  is a flow chart of a processing operation performed when the physical volume  400  has become not used at all. Next, explanation will be given on this case. 
   (1) When the physical volume  400  has become not used at all, the server  100  sets the state in the entry of the physical volume in the physical volume information  102  to “unused” and notifies the modification content to the controller  310  of the storage device  300  (steps  1901  and  1902 ). 
   (2) Upon reception of the aforementioned notification, the controller  310 , according to the modification content notified, sets the state in the entry to “unused” in the in-device physical volume information  311  and releases the SAN address of that entry, thereby terminating the processing (step  1903 ). 
     FIG. 23  is a flow chart showing a processing operation performed when a virtualized volume pair is deleted. Next, explanation will be given on this. 
   (1) Firstly, by using the snapshot information  104 , the server  100  identifies a virtualized volume of the source and that of the destination and initializes the snapshot attribute of the entry of the aforementioned virtualized volume (steps  2001  and  2002 ). 
   (2) Furthermore, the server  100  identifies a storage device  300  of the physical volume  400  constituting the aforementioned virtualized volume, deletes the entry of the aforementioned virtualized volume pair in the snapshot information  104 , and notifies the modification and deletion to the controller  310  of the aforementioned storage device  300  (steps  2003  to  2005 ). 
   (3) Upon reception of the notification, the controller  310  initializes the snapshot attribute of that entry in the in-device mapping information  312 , deletes the entry in the in-device snapshot information  313 , and synchronizes information between the server  100  and the controller  310 , thereby terminating the processing (steps  2006  and  2007 ). 
   In the aforementioned, as the interface and protocol for information updating and notification by the server  100 , the controller  310 , and the management terminal  800 , for example, it is possible to use MIB reference/update by the SNMP, CIM reference/update by XML document transferred by the HTTP, or the like. 
     FIG. 24  is a flow chart showing a processing operation performed for obtaining backup. Next, explanation will be given on this. 
   (1) Firstly, backup software on the host  200  requests the server  100  to obtain a snapshot with specifying a virtualized volume to be backed up (step  2101 ). 
   (2) Upon reception of the request, the server  100  performs the snapshot formation and division with respect to the storage device  300  and obtains a snapshot, i.e., a frozen image in the destination volume (steps  2102  and  2103 ). 
   (3) Next, the server  100  reports to the backup software of the host  200  that a snapshot is complete and notifies the aforementioned destination virtualized volume (step  2104 ). 
   (4) Upon reception of the report and notification, the backup software on the host  200  reads out data from the destination virtualized volume and writes the data into a backup storage device  500  to obtain a backup, thereby terminating the processing (step  2105 ). 
   The physical volume in the aforementioned processing may be a storage region of a magnetic disc device or a logical storage region such as provided by a magnetic disc device having a control device of RAID configuration. 
   In the aforementioned embodiment of the present invention, by performing the aforementioned processing, it is possible to perform management and control of the processing in the controller  310  of the storage device  300  according to a virtualized storage region and especially, it is possible to perform snapshot formation, management, and control in a virtualized region independently. 
   Furthermore, in the aforementioned embodiment of the present invention, an instruction about processing management and control in the controller  310  of the storage device  300  is performed according to a virtualized storage region, which simplifies management and control as well as reduces processing overhead. 
   In the aforementioned embodiment of the present invention, the storage device  300  has a snapshot formation function on volume basis of the physical volume  400  and explanation has been given on that the snapshot formation of a virtualized volume is realized by that the storage device  300  creates a snapshot of the physical volume  400  constituting the virtualized volume. However, even when the storage device  300  has a snapshot formation function not on a physical volume basis but a partial region basis of the physical volume  400 , an instruction about processing management and control in the controller  310  of the storage device  300  is performed according to a virtualized storage region. Thus, it is possible to simplify management and control and reduce the processing overhead. 
     FIG. 25  shows another example of the in-device physical volume information  311  and  FIG. 26  shows another example of the in-device snapshot information  313 . For example, the controller  310  has the in-device physical volume information  311  as shown in FIG.  25  and the in-device snapshot information  313  as shown in  FIG. 26 , and has a pair formation, division, combination functions and processes for a pair of a source physical volume range region and a destination physical volume range region and has a function and process for selecting destination region. In this case also, by the aforementioned processes, the same effects can be obtained. 
   In the aforementioned embodiment of the present invention, the storage device  300  has the controller  310 . However, the present invention can also be applied to a case when the controller  310  and the storage device  300  are separate devices. 
     FIG. 27  is a block diagram showing a computer system configuration according to another (second) embodiment of the present invention. In  FIG. 27 , a reference symbol  900  denotes back end connection means and the other reference symbols are identical to those in FIG.  1 . 
   In the embodiment of the present invention shown in  FIG. 27 , the controller  310  is provided as a separate device from the storage device  300  and connected to the network  700 . The controller  310  and the storage device  300  are connected to each other by the back end connection  900 . In this configuration also, it is possible to perform the processes same as those in the aforementioned (first) embodiment. The connection means  900  may be, for example, FC, IP, Infini Band, and the like. 
   The management terminal  800  references the aforementioned various information items held by the server  100  via the network  700  or the SAN  600  and can display them for a user. Moreover, according to a request from the user, the management terminal can set various information items via the network  700  or the SAN  600  such as formation/setting/deletion of a virtualized volume, making correspondence between the virtualized volume and the physical volume  400 , formation/setting/deletion of a virtualized volume pair, and the like. 
   As has been described above, according to the present invention, in an information processing system which virtualizes a storage region, it is possible to perform management and control of processing in a storage system according to a virtualized storage region. Especially, in the storage device system, it is possible to perform snapshot formation, management, and control according to a virtualized storage region independently. Moreover, according to the present invention, instructions of processing management and control in the storage device system can be performed according to a virtualized storage region. 
   It should be further understood by those skilled in the art that the foregoing description has been made on embodiments of the invention and that various changes and modifications may be made in the invention without departing from the spirit of the invention and scope of the appended claims.