Abstract:
Disclosed is a storage system having storage devices from which storage areas are specified. Virtualization apparatuses allocate the storage areas as virtual volumes and processes I/O requests with respect to the virtual volumes. A controller is operable to change the allocation of storage areas to the virtual volumes. The controller is configured to send a request to some of the virtualization apparatuses to temporarily suspend processing of their I/O. When a virtualization apparatus receives such a request, it completes its pending I/O and temporarily suspends subsequent I/O requests, and sends a completion report to the controller. The controller then changes the allocation of storage areas to the virtual volumes.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a storage system, and more particularly to a change in the allocation of a real storage area to a virtual volume in a storage system having a virtualization apparatus of a redundant configuration. 
   2. Description of the Prior Arts 
   In the so-called SAN (Storage Area Network), a system that sets a plurality of virtual volumes with reference to the storage area of a storage device and uses their volumes from a host processor via a network is known. 
   Regarding a storage virtualization apparatus that virtualizes the storage device connected through the network and enables input-output (I/O) from the host processor, for example, there is such a system as disclosed in Japanese Unexamined Patent Application Publication No. Hei 2000-242434 (Patent Reference 1). According to this art, a storage device to which a virtual storage area provided to a host is allocated is changed by installing switching equipment 20 between a storage device system 1 and a host 30 and the switching equipment 20 changes the virtualization setting of a virtual storage device system provided to the host 30, thereby to change the storage device to which a virtual storage area to be provided to a host is allocated. 
   The configuration information about the storage virtualization apparatus (for example, array disk switch) group described in Patent Reference 1 is managed independently for each storage virtualization apparatus. 
   In such a storage virtualization system, the modification of the configuration information during system operation changes the destination during input-output processing and causes data corruption and an input-output fault. Accordingly, a method for reducing the storage virtualization apparatuses that operate concurrently during a configuration change to only one apparatus can be considered, but a problem that concentration of a load or fault tolerance decreases is arisen. The aforementioned Patent Reference 1 does not refer to the modification of configuration information indicating that one volume shifts to another volume while the storage device system is operating. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to prevent data corruption and an input-output fault during system operation and change the configuration information about a storage virtualization apparatus in a storage system having a virtualization apparatus of redundant configuration. 
   The present invention is constructed in a plurality of virtualization apparatuses that process input-output to/from a host processor to a virtual volume on the condition that a request for temporarily holding the input-output processing accepted from the host processor after a certain point of time is issued to the plurality of virtualization apparatuses and a report indicating that the ongoing input-output processing was completed in regard to this request was received from each virtualization apparatus. On the condition, the present invention releases an input-output state held temporarily after having changed the allocation of the storage area of a storage device to each virtualization apparatus and having accepted a completion report of the allocation change from each virtualization apparatus. 
   As a desirable example concerning a storage system, the storage system having a storage device that can specify a plurality of storage areas and a plurality of virtualization apparatuses that allocate a storage area which this storage device has, form a plurality of virtual volumes, process the input-output from a host processor to one of the virtual volumes, and includes a configuration change controller for changing an allocation configuration of storage area of the storage device to the virtual volume. The configuration change controller has a means for requesting a temporary hold of the input-output to all the virtualization apparatuses before a configuration change and a means for allowing all the virtualization apparatuses that received this request to complete the input-output being processed and to subsequently shift to a state of temporarily holding an input-output request from the host processor subsequently, then to return a completion report to the configuration change controller. The configuration change controller has, when receiving the completion report from the previous plural virtualization apparatuses to which a request was issued, a means for instructing an allocation change of the storage area of the storage device to the virtual volume to the virtualization apparatus. 
   Further, as a desirable example regarding a plurality of virtualization apparatuses, they have a configuration change control program for changing a configuration of associating a virtual volume with a storage area that becomes a real area of the storage device and a first processor that executes the configuration change control program. This configuration change control program has, before changing the configuration of associating the virtual volume with the storage area that becomes the real area of the storage device, a means for requesting an input-output temporary hold to another virtualization apparatus. The other virtualization apparatus that received the request has a means for completing the input-output being processed and subsequently shifting to a state of temporarily holding an input-output request from a host processor, and returning a completion report. The configuration change control program has, when receiving the completion report from the other virtualization apparatus, a means for instructing an allocation change of the storage area of the storage device to the virtual volume to the other virtualization apparatuses, a means for receiving the completion report of the allocation change from another virtualization apparatus, and a means for sending an instruction for releasing the state of the input-output held temporarily to the other virtualization apparatus. 
   Furthermore, as an example of the configuration concerning a storage device, the storage device has a plurality of storage areas for providing a real storage area and a virtualization apparatus that allocates the plurality of storage areas, forms a plurality of virtual volumes, and processes the input-output from a host processor to one of the virtual volumes. This virtualization apparatus has, before changing a configuration of associating the virtual volume with the storage area that becomes a real area of the storage device, a means for requesting an input-output temporarily hold to another virtualization apparatus. The other virtualization apparatus that received the request has a means for completing the input-output being processed and subsequently shifting to a state of temporarily holding an input-output request from the host processor, and returning a completion report. The virtualization apparatus has, when receiving th completion report from the other virtualization apparatus, a means for instructing an allocation change of the storage area in regard to the virtual volume to the other virtualization apparatus, a means for receiving the completion report of the allocation change from the other virtualization apparatus, and a means for sending an instruction for releasing the state of the input-output held temporarily to the other virtualization apparatus. 
   As a more desirable example, data can migrate from one storage device to another storage device during system operation by copying the data between the storage devices synchronizing with the change of configuration information. Moreover, even a virtualization apparatus not having a copy function can migrate data by allowing the storage device to implement a configuration change control function and the aforementioned copy processing function. 
   According to the present invention, the configuration information of a virtual volume can be changed during system operation by preventing as much influence of an input-output temporary hold as possible. Consequently, data can migrate from one storage device to another storage device during system operation. Moreover, even a virtualization apparatus not having th copy function can shift data. A storage device that can change an allocation destination of the virtual volume can be realized during operation in a redundant configuration. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the present invention will be described in detail based on the followings, wherein: 
       FIG. 1  is a drawing showing the overall configuration of a storage system according to a first embodiment; 
       FIG. 2  is a drawing showing the internal configuration of a virtualization switch  11  of  FIG. 1 ; 
       FIG. 3  is a drawing showing the internal configuration of a configuration change controller  16  of  FIG. 1 ; 
       FIG. 4  is a drawing showing the table of a configuration information  221  in the storage system; 
       FIG. 5  is a drawing showing the communication protocol between a configuration change controller  16  and a virtualization switch  11  in the storage system of  FIG. 1 ; 
       FIG. 6  is a flowchart showing the processing of a configuration change control program  212  in a configuration change controller  16 ; 
       FIG. 7  is a flowchart showing the processing of a configuration management program  211  in a virtualization switch  11 ; 
       FIG. 8  is a flowchart showing processing of an I/O processing program  213  in the virtualization switch  11 ; 
       FIG. 9  is a drawing showing the internal configuration of the virtualization switch  11  according to a second embodiment; 
       FIG. 10  is a flowchart showing the processing of a configuration change control program  212  in the second embodiment; 
       FIG. 11  is a flowchart showing the processing operation of arbitration processing  600  in  FIG. 10 ; 
       FIG. 12  is a drawing showing the internal processing of the virtualization switch  11  according to a third embodiment; 
       FIG. 13  is a drawing showing the communication protocol between the configuration change controller  16  and the virtualization switch  11  in the third embodiment; 
       FIG. 14  is a drawing showing an example of a temporary hold control table  223  in  FIG. 12 ; 
       FIG. 15  is a drawing showing the table of the configuration information  221  in  FIG. 12 ; 
       FIG. 16  is a flowchart showing the processing of the configuration management program  212  in  FIG. 12 ; 
       FIG. 17  is a flowchart showing the processing of the configuration management program  211  in  FIG. 12 ; 
       FIG. 18  is a flowchart showing the processing of the I/O processing program  213  in  FIG. 12 ; 
       FIG. 19  is a drawing showing the internal processing of the virtualization switch  11  in a fourth embodiment; 
       FIG. 20  is a drawing showing the table of the configuration information  221  in  FIG. 19 ; 
       FIG. 21  is a flowchart showing the processing of the configuration change control program  212  in  FIG. 19 ; 
       FIG. 22  is a flowchart showing the details of copy processing  631  in the flowchart of  FIG. 21 ; 
       FIG. 23  is a flowchart showing the processing of the configuration management program  211  in  FIG. 19 ; 
       FIG. 24  is a flowchart showing the processing of the I/O processing program  213  in  FIG. 19 ; 
       FIG. 25  is a flowchart showing the processing of a copy processing program  214  in  FIG. 19 ; 
       FIG. 26  is a drawing for describing an operation principle of data migration in the fourth embodiment; 
       FIG. 27  is a drawing showing the overall configuration of the storage system in a fifth embodiment; 
       FIG. 28  is a flowchart showing the processing of the configuration change control program  212  in the fifth embodiment; and 
       FIG. 29  is a drawing showing the overall configuration of the storage system in a sixth embodiment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Embodiments of the present invention will be described below with reference to the drawings. 
   First, a first embodiment is described with reference to  FIGS. 1 to 8 . 
     FIG. 1  is a drawing showing the overall configuration of a storage system. 
   The storage system connects at least one host processor  12 , a plurality of storage devices  13 , a plurality of virtualization switches  11 , a configuration change controller  16 , and a management console  14  to a network  15  such as a LAN. 
   The host processor  12  is a computer that uses data stored in the storage device  13 . The host processor  12  may be a file server having a function provided to another computer that does not connect a storage area which the virtualization switch  11  provides to the virtualization switch  11 . 
   The storage device  13  is provided with a memory unit  13   a  or a memory unit system  13   b . In this case, the memory unit  13   a  is a single memory unit such as a hard disk drive or a DVD drive. The memory unit system  13   b  is a storage subsystem having the plural memory units  13   a  and a controller  1301  that controls these memory units. A memory unit  131  constructs the storage area of the memory unit  13   a  as a logical unit (hereafter referred to as an “LU”)  131 . The LU  131  is a logical storage area, and the device connected to the storage device  13  such as the host processor  12 , is recognized as one logically independent storage device. 
   Further, the logical unit  131  is provided with a plurality of partly logical storage areas (hereafter referred to as “real areas”)  132 . Each of the real areas  132  corresponds to a physical storage area which the storage device  13  has. The size of the real area  132  is arbitrary and the rang is an area having a continuous address. 
   The virtualization switch  11  is connected to another device through a communication line or by a switch as shown in the drawing and can communicate with another device. Further, the virtualization switch  11  is a virtualization apparatus that collects (“virtualizes”) the storage areas which the plural storage devices  13  connected to the virtualization switch  11  itself has as one or more storage areas. Then the virtualization switch  11  provides a virtualized storage area to the host processor  12  connected to the virtualization switch  11 . The virtual storage area which the virtualization switch  11  provides to the host processor  12  is hereafter referred to as a virtual volume  100 . 
   A protocol such as a fibre channel, is used in the communication line or switch used between the virtualization switch  11  and the host processor  12  and between the virtualization switch  11  and the storage device  13 . In this case, the communication line or switch used may be the communication line or protocol used in a local area network. The virtualization switch  11  is connected between the host processor  12  and the storage device  13  and has a function of transferring a command the host processor  12  issues to the side of th storage device  13 . 
   The virtual volume  100  is a virtualized storage area having at last the one real area  132 . The virtualization switch  11  can provide at least one virtual volume  100  to the host processor  12 . A unique identifier (hereafter referred to as a “virtual volume identifier”) is assigned to each virtual volume  100  in the virtualization switch  11  for specifying a virtual volume. Moreover, a continuous address is assigned to the storage area of each virtual volume  100 . The host processor  12  specifies an address indicating a virtual volume identifier and a location in the virtual volume  100  and accesses data stored in the storage device  13  instead of directly specifying the real area  132  within the LU  131  of the storage device  13 . 
   The management console  14  is such a personal computer (PC) that is used by a system administrator to create the virtual volume  100  and has a display device or an input device, and a memory. The management console  14  is connected to the virtualization switch  11  via the LAN  15  and can communicate with each other. 
   The configuration change controller  16  controls the virtualization switch  11  and controls configuration information, that is, the change of associating the virtual volume  100  with the real area  132 . The configuration change controller  16  can have a PC or a server, for example, and is connected to the virtualization switch  11  via the LAN  15 , which can communicate with each other. 
     FIG. 2  shows the internal configuration of the virtualization switch  11  of  FIG. 1 . 
   The virtualization switch  11  is provided with an input port  240 , an output port  250 , a transfer unit  230 , a processor  210 , a memory  220 , a bus  270 , and a communication unit  260 . The transfer unit  230 , processor  210 , memory  220 , and communication unit  260  are all connected to the bus  270 , and send and receive data to/from each other. 
   The input port  240  connects a communication line through which the virtualization switch  11  communicates with the host processor  12 . The output port  250  connects a communication line through which the virtualization switch  11  communicates with the storage device  13 . Further, the element constructing the input port  240  and the output port  250  may be located in the same hardware. In this case, the user selects which port is used as the input port or the output port. 
   The transfer unit  230  has an internal memory and holds a transfer information table  231  in the memory. The transfer information table  231  stores the interrelationship between the host processor  12  that can communicate with the virtualization switch  11  via each input port  240  and the storage device  13  that can communicate with the virtualization switch  11  via each output port  250 . 
   The transfer unit  230  refers to the transfer information table  231  and transfers an input-output request received from the host processor  12  via the input port  240  to the output port  250  that is used for the communication between the storage device  13  and the virtualization switch  11  of a requesting destination. Further, the transfer unit  230  transports the response information or data received from the storage device  13  via the output port  250  to the input port  240  that is used for the communication between the host processor  12  and the virtualization switch  11  which ought to receive the information or data. When the input-output request received from the host processor  12  is an input-output request to the virtual volume  100 , the transfer unit  230  enqueues the input-output request to an input queue  241  to be described later and requests the processing from the processor  210 . Further, the transfer unit transfers the input-output request stacked on an output queue  251  to be described later to the storage device  13  via the output port. 
   The processor  210  executes a program stored on the memory  220  and performs the input-output processing or the change processing of the configuration information for the virtual volume  100  from the host processor  12 . 
   The memory  220  stores the program the processor  210  executes and the information necessary for the execution. The program and data the memory  220  stores includes a configuration management program  211 , an I/O processing program  213 , the input queue  241 , the output queue  251 , a on-hold queue  242 , a in-process queue  252 , configuration information  221 , and a configuration information difference  222 . 
   The configuration management program  211  receives a request from the configuration change controller  16  and performs input-output temporary hold and restart processing or configuration information change processing. 
   The I/O processing program  213  processes the input-output processing for the virtual volume  100  from the host processor  12 , that is, converts the input-output to the input-output for the storage device  13  and transfers it. 
   The input queue  241  allows the transfer unit  230  to stack the input-output request for the virtual volume  100 . The output queue  251  stacks the input-output request for the storage device the I/O processing program  213  processed. The number of input queues  241  and the number of output queues  251  are optional. 
   The on-hold queue  242  stores the input-output request for the virtual volume  100  accepted when setting the virtualization switch  11  in a state (I/O temporary hold state) at which the input-output processing is held temporarily. The in-process queue  252  stores the input-output request for the virtual volume  100  processed by the virtualization switch  11  and transferred to the storage device  13  until the input-output is completed. 
   The configuration information  221  is the table for associating the virtual volume  100  with the real area  132 . The configuration information difference  222  is a buffer that records the difference before and after th change when the configuration information  221  is changed. 
   In this embodiment, one each of the on-hold queue  242 , in-process queue  252 , configuration information  221 , and configuration information difference  222  is provided for every virtualization switch  11 . 
   The communication unit  260  enables the processor  210  to communicate with the configuration change controller  16  and the management console  14  via the LAN  15 . 
     FIG. 3  shows the internal configuration of the configuration change controller  16  of  FIG. 1 . 
   The configuration change controller  16  is a management server, for example, and is provided with a processor  161 , a memory  162 , the bus  270 , and the communication unit  260 . The processor  161 , memory  162 , and communication unit  260  are all connected to the bus  270 , and send and receive data one after another. 
   The processor  161  executes the program stored on the memory  162  and controls the configuration change of the virtualization switch  11 . 
   The memory  162  stores the program the processor  161  executes or the information necessary for the execution. The program and data the memory  162  stores includes the configuration change control program  212 , configuration information  221 , and configuration information difference  222 . 
   The configuration change control program  212  controls the configuration change of the virtualization switch  11 . 
     FIG. 4  shows the table of the configuration information  221  in a storage system. The configuration information table  221  is provided in the virtualization switch  11  and the configuration change controller  16 . 
   The configuration information  221  is provided with entries that include a virtual volume address  41 , an offset  42 , a size  43 , an LU address  44 , and an offset  45 . Each entry is associated with a real area  132  and a partial area on the virtual volume  100  to which the real area  132  is allocated. The LU address  44  indicates the information for allowing the virtualization switch  11  to identify the LU  131  including the real area  132  that corresponds to the entry. The offset  45  indicates the start address on the LU  131  of the real area  132 , and the size  43  indicates the size of the real area  132 . 
   The virtual volume address  41  indicates the information for allowing the host processor  12  to identify the virtual volume  100 , and the offset  42  indicates the start address on the virtual volume  100  of the partial area that corresponds to the entry. The virtual volume address  41  and the LU address  44  specifically use a pair of a WWN (World Wide Name) or port ID, and a LUN (Logical Unit Number) of a fibre channel. 
   Next, the configuration change in this storage system is described briefly with reference to  FIG. 5 .  FIG. 5  shows th communication protocol between the configuration change controller  16  and the virtualization switch  11  in the storage system. 
   When an instruction of a configuration information change request is input from the management console  14 , the instruction is transferred to the configuration change controller  16  ( 501 ). Then the processing of steps  502  to  505  is executed and the input-output processing issued by the host processor  12  is held temporarily. This is because a conflict occurs if the input-output being processed exists before and after a configuration change. If the configuration information is changed during input-output processing in this manner, the input-output cannot be associated with the correct real area  132  and it may cause a data corruption. This data corruption is prevented from the following processing. 
   That is, the configuration change controller  16  that received a configuration instruction issues a request that temporarily holds the input-output processing (I/O temporary hold request) to all virtualization switches  11  ( 502 ). The virtualization switch  11  that received this hold request holds the input-output being processed and subsequent input-output processing temporarily and waits for the execution completion of the input-output being processed ( 503 ). After the execution is completed, the completion of the processing of the step  503  (I/O temporary hold completion report) is reported to the configuration change controller  16  ( 504 ). Subsequently, the configuration change controller  16  waits for the completion report from all the virtualization switches  11  ( 505 ). 
   The aforementioned processing enabled the change of configuration information. Subsequently, the processing of steps  506  to  509  is executed and the configuration information of all the virtualization switches  11  is changed collectively. This is because of the possibility of data corruption occurring when the input-output that corresponds to the same virtual volume is associated with the different real area  132  by the virtualization switch  11  in charge of processing if the consistency of the configuration information which the virtualization switch  11  has is not obtained. 
   The configuration change controller  16  sends a configuration information difference and a configuration information change request that used the difference to all the virtualization switches  11  ( 506 ). The virtualization switch  11  that received the request changes the configuration information ( 507 ). Then after the configuration change was completed, the virtualization switch reports the completion of the configuration information change to the configuration change controller  16  ( 508 ). Subsequently, the configuration change controller  16  waits for the completion report from all the virtualization switches  11  ( 509 ). 
   Finally, the processing of steps  510  to  513  is executed and the input-outputs held temporarily in the step  503  begin being restarted. 
   The configuration change controller  16  issues a request (I/O restart request) that restarts the input-output processing held temporarily to all the virtualization switches  11  ( 510 ). The virtualization switch  11  that received the request restarts the input-outputs that are held temporarily ( 511 ). Then the virtualization switch reports the completion of the restart processing to the configuration change controller  16  ( 512 ). Subsequently, the configuration change controller  16  waits for the completion report from all the virtualization switches  11  ( 513 ) and reports the completion to a management console ( 514 ). 
   The configuration change is enabled without generating a conflict of the configuration information during input-output processing (that is, system operation) or a conflict of the configuration information between the plural virtualization switches  11  in this manner. 
   Next, the processing operation of the configuration change control program  212  in the configuration change controller  16  is described with reference to  FIG. 6 . 
   First, the processor  161  issues an I/O temporary hold request to all the virtualization switches  11  and waits for a completion report from all the virtualization switches  11  ( 601 ). When queuing was completed normally ( 602  “Y”), the change of the configuration information  221  is enabled. In this case, the processor  161  sends a configuration change request and the configuration information difference  222  to all the virtualization switches  11  and changes the configuration information  221 . Then the processor waits for the completion report from all the virtualization switches  11  ( 603 ). When the queuing was completed normally ( 604  “Y”), the configuration information  221  is changed normally. Accordingly, to restart the input-output being held, the processor  161  sends an I/O restart request to all the virtualization switches  11  and waits for the completion report from all the virtualization switches  11  ( 605 ). When the queuing is completed normally ( 606  “Y”), the processor determines that all change processing has succeeded and returns a message indicating that the processing succeeded to the management console  14  ( 607 ). The aforementioned is a flow of the normal processing of the configuration change control program  212 . 
   On the other hand, when the virtualization switch  11  did not complete an I/O temporary hold request ( 602  “N”), it determines whether subsequent processing continues or not ( 608 ). 
   In this embodiment, when there are two or more of virtualization switches  11  to which a response of success was returned, the processing continues ( 608  “Y”). To prevent the virtualization switch  11  to which the response of success was not returned from being used, the virtualization switch is removed from a control range ( 611 ) and the processing continues from the step  603 . When several virtualization switches  11  are removed from the control range in the step  611 , they are utilized based on the incorrect configuration information  221  if the input-output of these virtualization switches  11  is restarted incorrectly. Accordingly, the processor  161  reports the virtualization switch  11  that was removed from the control range to the management console  14  in the step  607  and displays a message indicating “Several virtualization switches were stopped because the synchronization of the input-output temporary hold failed and configuration could not be changed during a configuration” change on the display device of the management console  14 ”. 
   Further, when the processing does not continue ( 608  “N”), the processor  161  first sends an I/O restart request to all the virtualization switches  11  and waits for the completion report from all the virtualization switches  11  ( 609 ), then determines whether the processing of the step  601  and later steps is retried or not ( 610 ). In this case, when the error in the step  602  was a timeout, this timeout is considered to result from the fact that because the virtualization switch  11  is processing a large amount of input-output, their completion can hardly be waited for. Accordingly, because there is the possibility of this completion wait proving successful by a retry, the retry is performed only for a predetermined count in this embodiment if there are no other errors ( 610  “Y”). In the step  610  and later steps, the processor  161  repeats processing from the step  601 . 
   On the other hand, when the processing is not retried ( 610  “N”), if there is the virtualization switch  11  to which a response of success was not returned in the step  609 , this switch is removed from the control range ( 617 ). Then the occurrence of an error and its cause are reported to the management console  14  and the management console displays a message indicating “An input-output completion wait of a virtualization switch failed” ( 616 ). More desirably, the management console  14  displays a message prompting the administrator to “Retry a configuration change when the input-output frequency from the host processor  12  to the virtual volume  100  is low”. 
   Further, when error detection, that is, the change of the configuration information  221  failed in the step  604 , the processor  161  returns to the original configuration information  221  ( 612 ,  613 ) and restarts the input-output ( 614 ,  615 ). Then the processor reports the occurrence of an error and its cause to the management console  14 , and, for example, displays a message indicating “The administrator failed in the change to the specified configuration information” ( 616 ). 
   When an error was detected in the processing of the steps  613  and  615  (for “N”), subsequent processing cannot continue. Accordingly, the processor  161  removes the virtualization switch  11  to which the response of success was not returned from the control range ( 617 ) and performs the processing of the step  616 . For example, the processor displays a message indicating “The administrator failed in the change to the configuration information and failed in even recovery processing”. The processor  161  controls the change of the configuration information  221  as described above. 
   Next, the processing operation of the configuration management program  211  in the virtualization switch  11  is described with reference to  FIG. 7 . 
   The configuration management program  211  is called when the virtualization switch  11  received any of an I/O temporary hold request, an I/O restart request, and a configuration information change request from the configuration change controller  16 . First, when the processor  210  received the I/O temporary hold request ( 701  “Y”), the processor calls the I/O processing program  213  and sets the I/O in a temporary hold state ( 702 ). Then when the transition to the temporary hold state succeeded ( 703  “Y”), the processor  210  returns a response of success to the processor  161  that executes the configuration change program  212  ( 704 ). 
   Next, when the processor  210  receives the configuration information change request ( 705  “Y”), the processor  210  confirms that the I/O is set in the temporary hold state ( 706 ). This is because the processor  210  does not change the configuration information  221  incorrectly during input-output processing. Further, the processor  210  changes the configuration information  221  ( 707 ). As a result, when the processor  210  was able to change the configuration information normally ( 708  “Y”), the processor executes the processing of the step  704 . 
   Moreover, when the processor  210  received the I/O restart request ( 709  “Y”), the processor confirms that the I/O is set in the temporary hold state ( 710 ). As a result, when the I/O is set in the hold state ( 710  “Y”), the processor  210  calls the I/O processing program  213  and releases the I/O temporary hold state, then restarts input-output ( 711 ). When the processor  210  was able to change the configuration information normally ( 712  “Y”), the processor executes the processing of the step  704 . The aforementioned is the normal path of the configuration management program  211 . 
   On the other hand, the configuration management program goes to an abnormal path if No (“N”) is selected in the steps  703 ,  706 ,  708 ,  710 , and  712 . In any case, an error and its cause are returned to the processor  161  ( 713 ). 
   The processor  210  can change the configuration information  221  in accordance with the instruction of the configuration change controller  16  by executing the configuration management program  211  in this manner. 
   Next, the processing operation of the I/O processing program  215  in the virtualization switch  11  is described with reference to  FIG. 8 . 
   The I/O processing program  213  is called when an input-output request was enqueued to the input queue  241 , when the input-output request of the in-process queue  252  was completed, when the I/O shifts to a temporary hold state by the processing of the configuration management program  211 , and when the I/Os temporary hold state are release according to the I/O restart request. 
   When the input-output request enqueued to the input queue  241  ( 801 ), the processor  210  processes the input-output request when the I/O is not set in the temporary hold state ( 802  “N”). That is, the processor  210  converts the address of the virtual volume  100  to the address of the LU  131  with reference to the configuration information  221  and enqueues the input-output request to the output queue  251  (hereafter referred to as the fact that the input-output request was processed). Then the processor enqueues the output-output request to the in-process queue  252  ( 803 ). Subsequently, the processor  210  executes an event wait ( 804 ) and waits for the following activation cause. 
   On the other hand, when the I/O is set in the temporary hold state ( 802  “Y”), the processor  210  enqueues the input-output request to the on-hold queue  242  ( 805 ) and executes the processing of the step  804  and later steps. 
   When the processor  210  completed the input-output request of the in-process queue  252  ( 807  “Y”), the processor dequeues the input-output request from the in-process queue  252  ( 808 ). Then the processor confirms whether the I/O is set in the temporary hold state or not ( 809 ). If the I/O is not set in the temporary hold state ( 809  “N”), the processor  210  executes the processing of the step  804  and later steps. 
   On the other hand, when the I/O is set in the temporary hold state ( 809  “Y”), the processor  210  verifies the in-process queue  252  ( 810 ). As a result of the verification, when the in-process queue  252  was empty ( 810  “Y”), the processor reports the transition completion to an I/O hold state to the configuration management program  211  ( 811 ) and completes the processing. To the contrary, when the in-process queue  252  is not empty ( 810  “N”), the processor  210  repeats the processing from the step  804 . 
   When the I/O shifts to the temporary hold state ( 812  “Y”), the processor  210  stores that the I/O was set in the temporary hold state ( 813 ,  814 ) and continues the processing from the step  810 . 
   Further, when receiving the restart request ( 815  “Y”), the processor confirms whether the I/O is set in the temporary state or not ( 816 ). As a result of the confirmation, if the I/O is set in the hold state, the processor releases the I/O temporary hold state and processes the input-output of the on-hold queue  242 , then enqueues to the in-process queue  252  ( 817 ). Then when the in-process queue was enqueued normally ( 818  “Y”), the processor executes the processing of the step  811  (that is, completion report). The aforementioned is the processing when the I/O processing program  213  was executed normally. 
   To the contrary, if the processing of the I/O processing program  213  is not normal, it indicates that No (“N”) was selected in the steps  814 ,  816 ,  818 . In these cases, because any processing cannot continue, an error and its cause are returned to the configuration management program  211  ( 819 ). 
   In this embodiment, the input-output processing during the change of the configuration information  221  that causes data corruption is prevented in the step  610  when the configuration change control program  212  is executed and a conflict of the configuration information  221  between the virtualization switches  11  that causes the data damage is prevented in the step  603  in the same manner. 
   Next, a second embodiment is described with reference to  FIGS. 9 to 11 . 
     FIG. 9  shows the internal configuration of the virtualization switch  11  in a storage system. 
     FIG. 9  differs from the virtualization switch  11  shown in  FIG. 2  in that the processor  161  connected to the bus  270  is provided, the configuration change control program  212  is stored in the memory  220 , and the processor  161  executes this configuration change control program  212 . In this case, the processor  161  is provided with a timer  165 , and the processing of the configuration change control program  212  is activated periodically by this timer  165 . The timer  165  may be a timer realized by software. 
   According to this embodiment, the virtualization switch  11  can function as the configuration change controller  16  by incorporating the configuration change control program  212  and the processor  161  in the virtualization switch  11  (the virtualization switch  11  that functions in this manner is also hereafter referred to as the configuration change controller  16 ). When the plural virtualization switches  11  are provided, they are all provided with the aforementioned configuration and can function as the configuration change controller  16 . If all the virtualization switches  11  are provided with the configuration change control program  212  and the processor  161  in this manner, the configuration change controller  16  in the system shown in  FIG. 1  becomes necessary. 
   The processor  210  provided in the virtualization switch  11  can use the function of the processor  161  simultaneously. 
     FIG. 10  shows the processing of the configuration change control program  212  in the second embodiment.  FIG. 10  differs from  FIG. 6  in that arbitration processing  600  is included as the processing operation of  FIG. 10 .  FIG. 11  shows a detailed flow of the arbitration processing  600 . 
   The arbitration processing  600  limits, among the plural processors  161  that correspond to the plural virtualization switches  11 , processors (hereafter referred to as a processor having a master right) that executes the processing of the step  601  and later steps to one processor. In this embodiment, the configuration change control program  212  is also activated by receiving a monitoring packet from another configuration change control program  16  (incorporated in the virtualization switch  11 ) and the timer  165  in addition to a configuration change request from the management console  14 . 
   In the flowchart of  FIG. 11 , first, when the processor  161  received a monitoring packet ( 1101  “Y”), the processor returns a response packet to the configuration change controller  16  that sent this monitoring packet ( 1102 ), completes the arbitration processing, and also completes the processing of the configuration change control program  212  ( 1110 ). 
   The monitoring packet and the response packet include the ID of the sent configuration change controller  16  and the ID (hereafter referred to as the ID of a controller having a master right) of the configuration change controller  16  that incorporates the processor having the master right. These identifiers identify the configuration change controller  16 . For example, the identifiers are IP addresses which the communication unit  260  has. When the processor  161  received a configuration change request from a management console ( 1103  “Y”), the processor  161  asserts the master right to another configuration change controller  16 , that is, the processor  161  sends the monitoring packet in which the ID of the local configuration change controller  16  was recorded as the ID of the controller having the master right to all the configuration change controllers  16  and waits for a response ( 1104 ). For a normal end, that is, when the processor did not receive the response packet that has the ID other than the local configuration change controller  16  as the ID of the controller having the master right ( 1105  “Y”), the processor completes processing and shifts to the processing of the step  601  of the configuration change control program  212  ( 1106 ). 
   In the step  1103 , when the program was called with the timing of the timer  165 , the processor  161  monitors the remote configuration change controller  16 , that is, sends the monitoring packet to the controller having the master right ( 1107 ). For the normal end, that is, when the processor received the response packet that has the ID of the controller as the ID of the controller having the master right ( 1108  “Y”), the processor advances to the processing of step  1110  and completes the processing. The aforementioned is the normal case of the arbitration processing. 
   To the contrary, for abnormal processing, that is, when negation (“N”) was selected in th steps  1105 ,  1108 , because there is another controller having the master right, the processor sends notice as such to the management console  14  ( 1109 ), the processor goes to the processing of the step  1110  and completes the processing. 
   Because another processing operation is the same as the aforementioned first embodiment, the description is omitted. 
   Thus, according to the second embodiment, the controller having the master right is limited to only the controller  16  that received a configuration change request from the management console  14  at first by the processing of the steps  1104 ,  1102 . That is, even if the plural processors  161  execute the configuration change control program  212  in a system, they can change the configuration information  221  without generating a conflict. 
   When a fault occurred in the controller  16  having the master right, the system administrator can identify this fault via the management console  14  through the processing of the steps  1107 ,  1102 . 
   Next, a third embodiment is described with reference to  FIGS. 12 to 18 . 
     FIG. 12  shows the internal configuration of the virtualization switch  11  in a storage system. 
   As compared with the virtualization switch  11  shown in  FIG. 9 ,  FIG. 12  differs in that a temporary hold control table  223  is provided, the plural in-process queues  252  are provided, and double-buffered configuration information  221   a ,  221   b  is provided. The processor is provided with the timer  215 . 
   The temporary hold control table  223  controls whether the input-output is held temporarily by storing the result of associating each entry of the configuration information  221  with the in-process queue  252 . The reason why the plural queues to be processed  252  are provided is to limit a completion wait and input-output held temporarily by dividing the in-process queues  252  according to an input-output destination address. The configuration information  221  has double-buffereds to shorten the processing time in the I/O temporary hold state by switching the face of the configuration information  221 . Further, the timer  215  is installed to set the processing of the I/O processing program  213  by the processor  210  and detect a timeout of the I/O temporary hold state. 
     FIG. 13  shows the communication protocol between the configuration change controller  16  and the virtualization switch  11  in the third embodiment. 
   In this embodiment, because only one virtualization switch enables a configuration change control function in the plural virtualization switches  11 , the communication becomes necessary between the virtualization switch  11  in which the configuration change control function is effective and the virtualization switch  11  the function of which is not effective. The communication protocol is the example shown in  FIG. 13 . The same communication is performed even in the same virtualization switch  11 . Accordingly, you are requested to assume that the “Configuration Change Control Function” shown in  FIG. 13  indicates the processor  161  of  FIG. 12  or the configuration change control program  212  that is executed there and the “Virtualization Switch  11 ” indicates the processor  210  in the local and remote virtualization switches  11  or the configuration management program  211  that is executed there and to refer to both. 
     FIG. 13  differs from the communication protocol shown in  FIG. 5  in that steps  531  to  533  are added between the steps  501  and  502 . Further, a configuration information switching request is sent instead of sending a configuration information change request in the steps  506  to  508  of  FIG. 5 . 
   In step  530 , the processor  161  sends the configuration information difference  222  to all the virtualization switches  11  ( 530 ). All the virtualization switches  11  store the configuration information difference and create the configuration information  221  ( 531 ). The virtualization switch  11  creates the face ( 221   b  here) that is not used by the I/O processing program  213  of the configuration information  221 . Subsequently, the virtualization switch  11  returns a configuration information difference receiving completion report to the configuration controller  16  ( 532 ,  533 ). 
   Further, in step  507 ′, the virtualization switch  11  switches the configuration information  221   a  to the configuration information  221   b . The processing time can be reduced because the processing during an I/O temporary hold state (between the steps  503  and  511 ) is completed only by switching the face of the configuration information  221  in the step  507 ′ in this way. 
     FIG. 14  shows an example of the temporary hold control table  223  in  FIG. 12 . 
   The temporary hold control table  223  has a plurality of entries. Each entry has a temporary hold state  2231  and a in-process queue ID  2232 . The temporary hold state  2231  and the in-process queue ID  2232  are both provided to limit a completion wait and input-output held temporarily. As the initial values of the temporary hold state  2231  and the in-process queue ID  2232 , the processor  210  stores the ID of the in-process queue  252  that is not in a temporary hold state and empty (not associated with the temporary hold control table  223 ) respectively when the virtualization switch  11  is initialized or when the virtual volume  100  is created. When the empty in-process queue  252  is provided, the processor  210  creates the in-process queue  252  anew and stores the ID as the ID  2232 . 
     FIG. 15  shows the configuration information  221  in  FIG. 12 . 
     FIG. 15  differs from the table with the table shown in  FIG. 4  in that an index  411  of the control table  223  is provided. The index  411  specifies the entry of the temporary hold control table  223 . The entry of the configuration information  221 , that is, the address range on the virtual volume  100  is associated with the temporary hold state  2231  and the in-process queue  252  through the entry of the temporary hold control table  223 . Accordingly, whether input-output is held temporarily per address range can be controlled. 
     FIG. 16  shows the processing of the configuration change control program  212  in the virtualization switches  11  shown in  FIG. 12 . 
     FIG. 16  differs from  FIG. 10  in that steps  625  and  626  are inserted next to the arbitration processing (step  600 ) and step  627  is inserted next to the step  602 . Further, steps  603 ′ and  612 ′ are included instead of the steps  603  and  612 . 
   The processing of the steps  625  and  626  is the same as the procedures  530 ,  533  of  FIG. 13 . In the step  627 , the processor  161  issues an I/O temporary restart request once ( 609 ) and retries the processing of the step  601  and later steps when the processor  210  detects a timeout of the I/O temporary hold state during processing of the I/O processing program  213  ( 627  “Y”). 
   In this step  627 , an I/O temporary hold state can be set prior to an input-output timeout by the host processor  12 . Further, in the steps  603 ′ and  612 ′, the processing of switching the configuration information from  221   a  to  221   b  is requested from the virtualization switch  11  instead of rewiring the configuration information  221 . Because the switching processing of the configuration  221  is completed in a shorter time than rewriting the configuration information to a memory, the time of the I/O temporary hold state can be reduced as a result. 
     FIG. 17  shows the processing of the configuration program  211  in the virtualization switch  11  of  FIG. 12 . 
     FIG. 17  differs from the flowchart shown in  FIG. 7  in that steps  714  to  718  were added next to the step  709  “N”. In the step  707 , among the configuration information  221 , the face ( 221   b ) which the I/O processing program  213  does not use is updated. The processing of steps  714  “Y” to  704  is the same as the steps  507 ′,  508 ′ of  FIG. 13 . 
   The configuration management program  211  is called when a request from the I/O processing program  213  is issued in addition to an I/O temporary hold request, an I/O restart request, a configuration information update request, and a configuration information switching request. When this request is provided, processing goes to the step  601  “N”. Subsequently, the processor  210  transfers the request of the I/O processing program  213  to the configuration change controller  16  ( 718 ). This processing can retry the processing in the configuration change control program  212  on a timeout of an I/O temporarily stopped state. 
   Further, the processing of the steps  705  to  704  is the same as the procedures  531 ,  532  of  FIG. 13 . 
     FIG. 18  shows the processing of the I/O processing program  213  in  FIG. 12 . 
     FIG. 18  differs from the flowchart of  FIG. 8  in the processing contents of the steps  802 ,  803 ,  805 ,  808 ,  809 ,  810 ,  813 ,  816 ,  817 . 
   In steps  802 ′,  809 ′,  816 ′, the processor  210  determines that the I/O is set in a temporary hold state by checking the temporary hold state  2231  of the entry the index  411  in the configuration information  221  specifies. This can control whether the input-output is held temporarily or not per address range of the virtual volume  100  that is an input-output destination. 
   Further, in steps  803 ′ and  808 ′, the processor  210  uses the in-process queue  252  specified with the ID  2232  of the in-process queue of the entry which the index  411  in the configuration information  221  specifies as the in-process queue  252 . 
   Further, in step  813 ′, the processor  210  changes a state so that only the input-output for an area on the virtual volume  100  defined according to the contents of the configuration information difference  222  can be set in the temporary hold state. Specifically, the processor  210  lists up the index  411  of the configuration information  221   a  that corresponds to all entries registered in the configuration information difference  222  and changes all the temporary hold states  2231  of the entry that corresponds to these indexes  411  during a temporary hold. As described already, in the step  802 ′, this temporary hold state  2231  is checked. Accordingly, the output-output request that corresponds to this temporary hold state  2231 , that is, only the input-output request affected by the configuration information difference  222  is held. 
   In step  810 ′, the processor  210  lists up the index  411  of the configuration information  221   a  that corresponds to all entries registered in the configuration information difference  222  and checks all the in-process queues  252  specified by the in-process queue ID  2232  of the entry that corresponds to these indexes  411 , then determines whether the in-process queue  252  becomes empty or not. 
   In step  805 ′, the processor  210  enqueues to the in-process queue  252  shown in the in-process queue ID  2232  and sets the timer  215 . In step  817 ′, the processor  210  resets the timer  215 , resets the temporary hold state  2231  held in step  813 ′, processes the input-output enqueued to the on-hold queue  242 , and enqueues to the queue be processed  252  shown in the in-process queue ID  2232 . 
   In the step  820  “Y”, the processor  210  starts the processing of the I/O processing program  213  on the timeout of the timer  215 . In this case, the processor  210  executes the processing of the step  819  and returns an error to a configuration management program. The processor  210  executes the processing of the step  818 . 
   Because other aspects are the same as the second embodiment, the description is omitted. 
   In the third embodiment, the time of the I/O temporary hold state can be reduced in the steps  625  and  603 ′ in this manner. The time of the I/O temporary hold state can be limited by releasing the I/O temporary hold state and retrying the processing in the steps  805 ′,  820 ,  627 . This can prevent the input-output timeout or performance deterioration in the host processor  12 . 
   Further, in this embodiment, it is possible to limit input-output temporarily held in steps  813 ′ and  802 ′ to a range affected by the configuration change. Accordingly, it is possible to prevent deterioration of performance by the configuration change. 
   As a modification example of this embodiment, there is also a method for being not provided with the aforementioned double-buffered configuration information  221  and not executing the processing of the step  625 . For example, the processing of the step  603  (rewriting of the configuration information  221  in the first embodiment) may also be performed instead of step  603 ′ in which the configuration information  221  is switched. In that case, although the time of the I/O temporary hold state is prolonged, the capacity of the memory  220  can be suppressed. 
   Next, a fourth embodiment is described with reference to  FIGS. 19 to 26 . 
     FIG. 19  shows the internal configuration of the virtualization switch  11  in the fourth embodiment. 
     FIG. 19  differs from the configuration shown in  FIG. 12  in that a copy processing program  214  and a copy progress table  224  are added and the one-face configuration information  221  is provided. 
   When the copy processing program  214  is executed by the processor  210  and changes the LU  1311  to which the virtual volume  100  corresponds to the other LU  1312 , the program copies data from the LU  1311  to the LU  1312 . The copy progress table  224  is used to manage advancement of the copy processing in the copy processing program  214  and has a plurality of entries. Each entry corresponds to the real area  132  that constructs the LU  131 . In this embodiment, the configuration information difference  222  is generated during I/O temporary stop. Accordingly, the configuration information  221  has only one face. Other aspects are the same as  FIG. 12 . 
     FIG. 20  shows an example of the configuration information  221  in the virtualization switch  11  of  FIG. 19 . 
   As compared with  FIG. 15 , in  FIG. 20 , a total of three pairs of the LU address and offset consisting of on pair of  44  and  45  for the Read command and two pairs of  46  and  47 , and  48  and  49  for the Write command are provided. In this embodiment, the correspondence of the virtual volume  100  differs in the Write and Read commands due to the progress of the copy processing program  214 . Further, in the case of Write operation, because dual writing is also performed to the LU  1311  and the LU  1312 , two pairs of the address and offset for the Write command are prepared. 
     FIG. 21  shows the processing of the configuration change control program  212  in the virtualization switch  11  of  FIG. 19 . 
   As compared with the flowchart of  FIG. 16 , in  FIG. 21 , steps  631  to  633  and  635  are added between the steps  627  and  603  and step  634  is added between the steps  606  and  607 . Further, the processing of the steps  603 ,  612  is performed instead of the steps  603 ′,  612 ′. 
   In the copy processing  631 , the processor  161  starts the copy processing program  214 . When copying is performed without any error ( 632  “Y”), the processor  210  refers to the copy progress table  224  and creates the configuration information difference  222 . The details of difference creation will be described later with reference to  FIG. 26 . 
   In the step  634 , the processor  161  determines whether the copying from the LU  1311  to the LU  1212  was all completed by checking the copy progress table  224 . When the copying is completed ( 634  “Y”), the processor  161  executes the processing of the step  607  and completes the processing. On the other hand, when the copying is not completed ( 634  “N”), the processor  161  repeats the processing from the step  601 . 
   When the copying ended abnormally ( 632  “N”), the processor  161  performs recovery processing ( 635 ). Specifically, the processor  161  creates the difference  222  so that the configuration information  221  before executing the configuration change control program  212  can be returned and issues a configuration change request to all the virtualization switches  11 , then waits for the completion. Further, the processor  161  executes the processing of the step  614  and later steps and reports an error to a management console, then completes the processing. 
     FIG. 22  shows the detailed processing operation of the copy processing  631  shown in the flowchart of  FIG. 21 . 
   First, the processor  161  sends a copy start request to the processor  210  and activates the copy processing program  214  ( 6312 ) after activating the configuration change control program  212  and then activating first copy processing  6311  ( 6311  “Y”). with the copy start request, the processor  161  instructs the address range in which copying is performed by the activation of the copy processing program  214  to the processor  210 . 
   On the other hand, when no initial activation is performed ( 6311  “N”), the processor sends the copy restart request to the processor  210  and activates the copy processing program  214  ( 6313 ). Also in this case, the processor instructs the address range in which the copying is performed by the activation of this copy processing program  214  to the processor  210 . In both cases, the processor  161  subsequently enters an event wait state ( 6314 ). The events for which the processor  161  waits are the completion of the copy processing program  214  and the receiving of a copy priority request or a copy interrupt request in step  718  to be described later. When the processing of the copy processing program  214  was completed ( 6315  “N”,  6316  “N”), the processor  161  shifts to step  632 . 
   For the copy interrupt request ( 6315  “Y”), the processor sends the copy interrupt request to the processor  210  and activates the copy processing program  214  ( 6317 ). For the copy priority request, the processor interrupts the copying once and performs the processing from the step  6315 . Subsequently, because the copy processing must be reactivated, the processor  161  executes the step  6316  “Y” and repeats the processing of the step  6313  and later steps. At that time, because the processor transfers an address to be copied preferentially from the processor  210 , it specifies the range that includes the address in the step  6313 . 
   As described in the steps  6312  and  6313 , the copy processing program  214  is activated plural times. Further, in the step  6317 , the copying is interrupted once. Consequently, the time the input-output is held temporarily can be reduced. 
     FIG. 23  shows the processing of the configuration management program  211  in the virtualization switch  11  of  FIG. 19 . 
   In this embodiment, because the face of the configuration information  221  is not switched during I/O temporary hold state, the processing of the configuration management program  211  is similar to that shown in the first embodiment. Accordingly, when  FIG. 23  is compared with the flowchart of  FIG. 7 ,  FIG. 23  differs from  FIG. 7  in that step  718  is added. 
   In this embodiment, the timing the configuration management program  211  is called is caused by a copy priority request or a copy interrupt request from the I/O processing program  213  in addition to the case of  FIG. 7 . In either case, the processor  210  determines as No in step  709  and issues the copy priority request or copy interrupt request to the processor  161  ( 718 ). For the copy priority request, however, because the processor  210  transfers an address to be copied preferentially from the I/O processing program  213 , it also transfers the address to the processor  161 . 
   Thus, the configuration management program  211  reflects a request caused by the processing of the I/O processing program  213  in the processing of the configuration change control program  212  by the processing of the step  718 . 
     FIG. 24  shows the processing of the I/O processing program  213  in the virtualization switch  11  of  FIG. 19 . 
   In comparison with the flowchart shown in  FIG. 18 , in  FIG. 24 , step  806  is added next to the step  805 ′ and step  821  is added next to the step  820 . 
   In the step  806 , the processor  210  calls the configuration management program  211  and requests copy priority when the accepted input-output is Write operation. In that case, the processor transfers the address range written by the accepted input-output to the configuration management program  211 . 
   In this embodiment, because the timeout ( 820  “Y”) of the timer  215  is caused by the copy processing, in the step  821 , the processor  210  calls the configuration management program  211  and requests a copy interrupt. 
   When the copy processing by the input-output held temporarily is interrupted or made to take preference by the processing of the steps  806  and  821 , the time the input-output is held temporarily can be reduced. 
   In step  806 , by making a copy interrupt request when the accepted input-output is read, the time the input-output is held temporarily can be further reduced (In this case, the step  821  becomes unnecessary). The copy processing, however, is as delayed as this operation. 
     FIG. 25  shows the processing of the copy processing program  214  in th virtualization  11  of  FIG. 19 . 
   The copy processing program  214  is activated at the timing of the completion of a copy start request, a copy restart request, and a copy interrupt request from the configuration change control program  212 , and the input-output that copies data actually. When the copy start request is provided ( 901  “Y”), the processor  210  initializes all the entries of the copy progress table  224  to a value (“0” in this example) that indicates Uncopied ( 902 ). Subsequently, the entry of the copy progress table that corresponds to the address range transferred from the configuration change control program  212  is set to a value (“1” in this example) that indicates Being Copied ( 903 ). 
   Further, the processor  210  issues an input-output instruction (hereafter referred to as COPY I/O) that performs copying to the area set to “1” (Being Copied) in the copy progress table  224  ( 904 ). Specifically, the input-output request that performs copying is generated and enqueued to the output queue  251 . Further, the processor  210  waits for an event ( 905 ). Among the activation timings of the copy processing program  214 , the processor waits for a request: other than the copy start request and executes the processing of step  906  and later steps. Further, when the copy restart request was provided ( 906  “Y”), the processor  210  repeats the processing of the step  903  and later steps. 
   When COPY I/O is completed ( 907  “Y”), the processor  210  confirms that the result of this input-output ends normally ( 908  “Y”) and updates the copy progress table  224  ( 909 ). Specifically, the processor sets a value (“4” in this example) that indicates Copied in an entry where COPY I/O was completed and sets a value that indicates a copy interrupt (in this example, “0” (Uncopied) in the entry in which “2” is stored). Further, when there is no entry in which “1” (Being Copied) in the entry of the copy progress table  224 , the processor  210  returns a response of success to the configuration change control program  212  and completes the processing ( 911 ). When there is an entry being copied ( 910  “N”), the processor  210  repeats the processing from the step  904 . 
   When the copy interrupt request is received ( 912  “Y”), the processor  210  sets “2” (Copy Interrupted) in all entries where “1” of the copy progress table  224  is set and repeats the processing from the step  905 . 
   When COPY I/O ended abnormally ( 908  “N”), the processor  210  sets “0” (Uncopied) in all entries where “1” (Being Copied) and “2” (Copy Interrupted) of the copy progress table  224  are set ( 914 ). Then an error and its cause are returned to the configuration change control program  212  and the processing terminates ( 915 ). 
   The copy processing program  214  can copy data by the processing of the COPY I/O of the step  904  in this manner. 
   The operation principle of data migration according to the fourth embodiment is described with reference to  FIG. 26 . 
     FIG. 26A  shows the interrelationship between the virtual volume  100  and th real area  132 , and the interrelationship with the copy progress table  224  in the copy processing  631 . 
   The arrow from the real area  132  to the virtual volume  100  shows the interrelationship in a Read request to the virtual volume  100  and the arrow from the virtual volume  100  to the real area  132  shows the interrelationship in a Write request to the virtual volume  100 . An arrow marked by a dotted line shows that the input-output to this arrow is held. 
   Arrows appear from an area  1001  on the virtual volume to a real area  13211  and a real area  13221 . This indicates that the same data is written dually to the two real areas  13211 ,  13221  when the Write request is issued to  1001 . 
   Further, the arrows from real areas  13212 ,  13213  to real areas  13222 ,  13223  indicate copying is performed in this direction.  2241   a ,  2242   a ,  2243   a ,  2244   a  of the copy progress table correspond to areas  1001 , 1002 ,  1003 ,  1004  on the virtual volume. 
     FIG. 26A  shows that  2241   a  is set to Copied “4” and the copying from the real area  13211  to real  13221  is completed regarding an area  100 - 1 . Regarding the copied area, for Read, data is written from a shift destination, that is,  1311 , and, for Write, data is written to both shift source and shift destination, that is, both  1311  and  1312 . This is because the latest data is left in the LU  1311  even when the shift into the LU  1312  failed halfway. 
   Further,  2242   a  to  2244   a  are set to Being Copied “1” and indicate that data is copied currently from these corresponding real areas  13212  to  13214  to the real areas  13222  to  13224 .  2245   a  is set to Uncopied “0” and indicates copying is not performed from a real area  13215  to a real area  13225 . 
     FIG. 26B  shows the copy progress table  224  after the host processor  12  issued a Write request to the area  1004 . When Write to the area being copied is received, the processor  210  requests copy priority through the step  806  of the I/O processing program  213  ( FIG. 24 ). Subsequently, the processor  161  first performs copy interrupt processing  6317  of the copy processing  631 . As a result, the processor  210  executes the step  912  of the copy processing program  214 . Because the mark “2” of Copy Interrupted is set in the area of Being Copied “1” of the copy progress table  224 , the state of Table  224   b  occurs. 
   Subsequently, the processor  210  waits for the completion of COPY IO and executes the processing of the step  909 , then updates the copy progress table  224 . In this case, if copying to the real area  13222  only is completed, the entry  2242   b  that corresponds to this is updated from Copy Interrupted “2” to Copied “4” and another entry is updated from the mark “2” of Copy Interrupted to the mark “0” of Uncopied. Further, the processor  161  performs the processing of the step  6313  in th copy processing  631  and specifies the address of the real area  13214  to the area  1004 . Because the processor  210  performs the processing of the step  906  and later steps of the copy processing program  213 , the processor  210  sets the mark “1” of Being Copied in  2244   b  that corresponds to the area  1004 . Thus the processor enters the state of  FIG. 26C . That is, the processor  210  preferentially copies data from the real areas  13214  to  13224 . 
   Because other processing is the same as the third embodiment, the description is omitted. 
   As described above, the allocation destination of the virtual volume  100  can shift the allocation destination of the virtual volume  100  from the one LU  1311  to the other LU  1312  during system operation. 
   Next, a fifth embodiment is described with reference to  FIGS. 27 and 28 . 
     FIG. 27  shows the overall configuration of a storage system. 
   As compared with the system shown in  FIG. 1 , in  FIG. 27 , the independent configuration change controller  16  is removed, and a configuration change control program  16 ′ is provided in each virtualization switch  11 . Further, a storage device  135  has a copy control unit  136 . 
   The storage device  135  differs from the storage device  13  and has the communication unit  260 . The storage device  135  is connected to the LAN  15  and has the copy control unit  136 . This enables data to be copied from an LU  131   a  within the local storage device  135  to an LU  131   c . Desirably, the copy control unit  136  provided in the storage device  135  should perform copy processing while permitting the input-output from the host processor  12  to the copy source UL  131  (hereafter referred to as ‘Copiable’ during online operation). Needless to say, ‘Copiable’ need not be required during online operation. When copying is not enabled during this online operation, the time the input-output is held temporarily is prolonged. 
   The copy control unit  136  receives the designation of performing the copy processing from which LU  131  to which LU  131 , for example, of copying data from the LU  131   a  to the LU  131   b  as well as the request of the start or completion of the copy processing from the configuration change controller  16  or the management console  14  via the communication unit  260 . 
     FIG. 28  is a flowchart showing the processing of the configuration control program  212  in the fifth embodiment. 
     FIG. 28  differs  FIG. 16  in that the processing of the step  640  is inserted after the step  627 . 
   In the processing of the step  640 , the processor  161  requests to the copy control unit  136  the completion of the copy processing from the LU  131   a  to the LU  131   b  and waits for the completion report. When copying is enabled during online processing, the system administrator can request copy start at an optional period before the step  640 . When copying is disabled during online processing, the processor  161  requests to the copy control unit  136  the start of the copy processing in the step  640  prior to the request of the completion. By hastening the request of the copy start, it can be anticipated that await completion report in the step  640  is returned quickly. 
   The processors  161  and  210  perform the same processing as the third embodiment and changes the configuration so that the virtual volume  100  can correspond to the LU  131   a  and the LU  131   b . Because other processing is the same as the third embodiment, the description is omitted. 
   According to the fifth embodiment, by utilizing the copy function which the storage device  135  has, the allocation destination of the virtual volume  100  can be shifted from the LU  131   a  to the LU  131   b  even if the function of copying the LU  131  to the virtualization switch  11  is not provided. 
   Next, yet another example (sixth embodiment) of a storage system is described with reference to  FIG. 29 . 
   In this example, a storage device  137  has a virtualization function. Each storage device  137  has the storage device  13 , copy control unit  136 , and communication unit  260  and the virtualization switch  11  shown in  FIG. 27 . Each virtualization switch  11  incorporates the configuration change control program  16 ′ similarly to the aforementioned  FIG. 27  and implements the configuration change control function. Because other aspects are the same as the fifth embodiment, the description is omitted. 
   According to this example, while the system is operating by a virtualization switch having a redundant configuration, a storage device that can shift the allocation destination of the virtual volume  100  from the LU  131   a  to the LU  131   b  can be realized. 
   Although several embodiments have been described above, the present invention can be modified variously and executed without being limited to the above examples. For instance, in the examples of  FIGS. 12 and 19 , one of the processors  161  and  210  is omitted and the remaining other processor can be used for the processing of a program at the same time.