Storage apparatus and storage apparatus migration method

FIG. 1 is a drawing showing an example of the configuration of a computer system related to Example 1.

The computer system comprises one or more hosts (host computers) 200 , and a remote computer system. The remote computer system comprises multiple DKCs (storage apparatuses) 100 .

The host 200 is an ordinary computer, comprising a processor, a cache, and a storage apparatus. The host 200 issues the DKC 100 an access command (a read command (read request) or a write command (write request)) specifying an ID (for example, a LUN) of a VOL (for example, a PVOL 105 ) provided by the DKC 100 . The access command, for example, is a SCSI command. The host 200 also comprises one or more ports 201 . The port 201 is an example of a communication interface device, and is an interface for coupling to a network 50 . Identification information (for example, a world wide name (WWN) or the like) that makes it possible to uniquely identify a port 201 is configured in the port 201 . The host 200 stores path management information. The path management information is information, about a path to a DKC 100 , in which identification information (for example, a device number) of an access-target VOL has been associated with identification information (port information) of a port 101 in a DKC 100 to be accessed when accessing the VOL.

A MS-PDKC 100 A and a SDKC 100 B are coupled via a communication network 60 . The MS-PDKC 100 A and a MD-PDKC 100 C, for example, are installed at the same local site 10 , and are communicably coupled to one another. However, the MD-PDKC 100 C may also be installed at a site that is separate from the MS-PDKC 100 A. The SDKC 100 B is installed at a remote site 20 , which is a place separate from the local site 10 . The MD-PDKC 100 C and the SDKC 100 B are coupled via the communication network 60 .

The DKC 100 ( 100 A through 100 C), for example, comprises multiple ports 101 , one or more microprocessor packages (MPPKs) 102 , one or more cache memory packages (CMPKs) 103 , an internal network 104 , and a PDEV configuring one or more VOLs. The port 101 , MPPK 102 , CMPK 103 , and VOL-configuring PDEV are communicably coupled via the internal network 104 . A group of an MPPK and a CMPK is called a storage controller.

For example, as a VOL managed by a DKC 100 , the MS-PDKC 100 A manages a PVOL 105 . The SDKC 100 B manages a SVOL 110 . The MD-PDKC 100 C manages a MD-PVOL 112 .

The port 101 is an example of a communication interface device, and is an interface for connecting to a network. Identification information (for example, a world wide name (WWN) or the like) that makes it possible to uniquely identify a port is configured in the port 101 . Arbitrary identification information (virtual identification information) can be virtually allocated to the port 101 , and this virtual identification information can be used in communications.

In this example, for example, the MS-PDKC 100 A comprises a port 101 for coupling to the host 200 , a port 101 for coupling to the MD-PDKC 100 C, and a port 101 for coupling to the SDKC 100 B.

The MD-PDKC comprises a port 101 for coupling to the host 200 , a port 101 for coupling to the MS-PDKC 100 A, and a port 101 for coupling to the SDKC 100 B.

The SDKC 100 B comprises a port 101 for coupling to the host 200 , a port 101 for coupling to the MS-PDKC 100 A, and a port 101 for coupling to the MD-PDKC 100 C.

The MPPK 102 is a control device comprising either one or multiple processors. The processor executes various processes in accordance with a program. The MPPK 102 may comprise a memory for storing a program executed by the processor, and data to be used. In this example, the MPPK 102 of the MD-PDKC 100 C comprises a program for realizing a new function in this example, which will be explained further below. The MPPK 102 in the MS-PDKC 100 A and the SDKC 100 B may comprise existing programs.

The CMPK 103 includes one or more cache memories. The one or more cache memories are a volatile memory and/or a nonvolatile memory. The one of more cache memories may comprise, in addition to a storage area (hereinafter, cache area) for temporarily storing data input/output to/from the PDEV, a storage area (hereinafter, shared area) for storing information that is used by the MPPK 102 processor.

FIG. 2 is a drawing showing an example of the configuration of the computer system in an initial state prior to starting a migration.

The computer system, in the initial state, comprises a host 200 , a MS-PDKC 100 A, and a SDKC 100 B.

The MS-PDKC 100 A comprises a MS-PVOL 105 , a primary journal VOL (PJVOL) 108 for storing a journal (JNL) showing update content for the MS-PVOL 105 , and sequence information (one example of sequence information, also referred to as write sequence information) 109 for storing the latest sequence number (SEQ #) allocated to the journal. The storage area in which the journal is stored is a single VOL in this example, but may be a storage area provided in a different storage device such as the CMPK 103 . The sequence number is information showing the write sequence for a primary volume.

The SDKC 100 B comprises a SVOL 110 that configures a pair with the MS-PVOL 105 , and a secondary JVOL (SJVOL) 111 for storing a journal acquired from the MS-PDKC 100 A.

A path h-m 1 is formed between the host 200 and the MS-PDKC 100 A. For example, an SCSI command such as either a read command or a write command is sent from the host 200 to the MS-PDKC 100 A via the path h-m 1 .

A path m 1 -r is formed between the MS-PDKC 100 A and the SVOL 100 B. For example, a command (asynchronous remote copy command) is sent from the SDKC 100 B to the MS-PDKC 100 A via the path m 1 -r. As a command that is sent, for example, there is a command (read journal command (RDJNL)) for reading a journal (update information including journal data and a sequential number) of the PJVOL 108 in the MS-PDKC 100 A.

Next, the MD-PDKC connections configuration processing in preparation for migrating a PVOL will be explained.

FIG. 3 is a flowchart of MD-PDKC connection configuration processing. FIG. 4 is a drawing illustrating the MD-PDKC connection configuration processing.

First, the administrator installs the MD-PDKC 100 C for storing the MD-PVOL 112 , for example, at the local site 10 (Step S 11 , FIG. 4 ( 1 )). At this point in time, the MD-PDKC 100 C is physically coupled to the networks 50 and 60 , and is also physically coupled to the MS-PDKC 100 A.

Next, the administrator connects a path m 1 -m 2 between the MS-PDKC 100 A and the MD-PDKC 100 C (Step 12 , FIG. 4 ( 2 )). As the method for connecting the path here, there is a method in which the administrator makes the configurations using a terminal of a service processor (SVP) coupled to the MD-PDKC 100 C and/or a not-shown management apparatus or the like coupled via a network. There may be cases where the operations and configurations performed by the administrator using the SVP or other such terminal is explained giving the “administrator” as the doer of the action without specifying the terminal or the like, but the actual doer of the action may be interpreted as the management apparatus. In this example, virtualization is performed on this path so that the MD-PDKC 100 C appears as the host 200 to the MS-PDKC 100 A. Specifically, the identification information (port information) of the port 101 in the MD-PDKC 100 C that configures this path is virtualized to the same identification information as the identification information of the port 201 (port 201 connected to the path h-m 2 ) in the host 200 . In accordance with this, the MS-PDKC 100 A perceives communications carried out using this path as being with the host 200 , and does not need to be aware of the MD-PDKC 100 C.

Next, the administrator connects a path h-m 2 between the host 200 and the MD-PDKC 100 C (Step S 13 , FIG. 4 ( 3 )). In this example, virtualization is performed on this path at this time so that the MD-PDKC 100 C appears as the MS-PDKC 100 A to the host 200 . Specifically, the identification information (port information) of the port 101 in the MD-PDKC 100 C that configures this path is virtualized to the same identification information as the identification information of the port 101 (port 101 connected to the path m 1 -m 2 ) in the MS-PDKC 100 A. In accordance with this, the host 200 perceives communications carried out using this path as being with the MS-PDKC 100 A, and does not need to be aware of the MD-PDKC 100 C.

Next, path-switching software 202 in the host 200 (or, an FC switch that exists between the host 200 and the DKC) adds a path (path h-m 2 ) that goes through the MD-PDKC 100 C as the path between the host 200 and the MS-PDKC 100 A (Step S 14 ). Thereafter, the MD-PDKC 100 C (specifically, the MPPK 102 processor in the MD-PDKC 100 C), upon acquiring a SCSI command from the host 200 for the MS-PDKC 100 A via the path h-m 2 , transfers this SCSI command to the MS-PDKC 100 A via the path m 1 -m 2 ( FIG. 4 ( 4 )).

Next, path-switching software 202 in the host 200 (or, an FC switch that exists between the host 200 and the DKC) deletes the path (path h-m 1 ) between the host 200 and the MS-PDKC 100 A that does not go through the MD-PDKC 100 C (Step S 15 , FIG. 4 ( 5 )). Before deleting the path (path h-m 1 ) that does not go through the MD-PDKC 100 C, a check may be performed to make sure the command transfer via the path that goes through the MD-PDKC 100 C is operating normally. In accordance with this, an SCSI command for the PVOL 105 transferred from the host 200 to the MS-PDKC 100 A always goes through the MD-PDKC 100 C. Therefore, an SCSI command for the PVOL 105 can reliably be discerned in the MD-PDKC 100 C.

After the MD-PDKC connection configuration processing has ended, it is possible to start PVOL migration processing for migrating the PVOL 105 of the MS-PDKC 100 A to the MD-PDKC 100 C.

Next, the PVOL migration processing will be explained.

FIG. 5 is a flowchart of the PVOL migration processing. FIG. 6 is a drawing illustrating the PVOL migration processing.

The MD-PDKC 100 C prepares, on the PDEV, a VOL (MD-PVOL 112 ) having a capacity of equal to or greater than the PVOL to be used as the migration destination for the MS-PVOL 105 (Step S 21 , FIG. 6 ( 1 )). At this point, the MD-PDKC 100 C manages a difference bitmap 113 for managing the migration status of the PVOL 105 data in the MD-PVOL 112 . The difference bitmap 113 includes bits corresponding to multiple areas (for example, blocks) of the MD-PVOL 112 , and, in accordance with the values of these bits, shows whether or not the PVOL 105 data is being migrated (copied) to these areas. Furthermore, for example, in a case where the migration is to be performed sequentially to the MD-PVOL 112 beginning with the data in the area at the start of the PVOL 105 , management may be performed to determine the area down to which migration has been completed without the need to manage the difference bitmap 113 .

Next, the MD-PDKC 100 C updates the values of all the bits in the difference bitmap 113 to values showing that the data migration is not complete (Step S 22 ).

Then, the MD-PDKC 100 C assumes control and executes the processing of loop (A) (Step S 24 through Step S 28 ) targeted at the addresses of the areas for which the MS-PVOL 105 data migration has yet to be completed, thereby executing the data migration from the MS-PVOL 105 to the MD-PVOL 112 ( FIG. 6 ( 2 )). In the explanation of the processing in the loop (A), an address targeted for processing will be referred to as a target address.

Specifically, the MD-PDKC 100 C, posing as the host 200 , sends a read command for reading the target address of the MS-PVOL 105 in the MS-PDKC 100 A (Step S 24 ). Upon receiving this read command, the MS-PDKC 100 A reads the data of the PVOL 105 target-address in accordance with the read command (Step S 25 ), and sends the read result and the data that was read (read data) to the source of the read command (Step S 26 ). The MS-PDKC 100 A perceives the read command source as being the host 200 here, and as such, perceives that the read result and the read data are being sent to the host 200 , but actually the read result and the read data are sent to the MD-PDKC 100 C posing as the host 200 .

The MD-PDKC 100 C writes the read data received from the MS-PDKC 100 A to the target address in the MD-PVOL 112 (Step S 27 ), and updates the bit of the area corresponding to the target address in the difference bitmap 113 to a value showing that data migration has been completed (Step S 28 ).

Then, after executing the loop (A) processing for all of the addresses in the MS-PVOL 105 for which data migration has not been completed, the MD-PDKC 100 C ends the processing.

According to this processing, all of the data in the PVOL 105 in the MS-PDKC 100 A is migrated to the MD-PVOL 112 in the MD-PDKC 100 C.

Next, the read command processing in a case where the MD-PDKC 100 C has received a read command from the host 200 with respect to the PVOL 105 part way through a PVOL migration process will be explained.

FIG. 7 is a flowchart of read command processing at the time of a PVOL migration. FIG. 8 is a drawing illustrating the read command processing at the time of the PVOL migration.

The MD-PDKC 110 C, upon receiving a read command from the host 200 with respect to the PVOL 105 , refers to the difference bitmap 113 , and determines whether the value of the bit corresponding to an address targeted by the read command (referred to as the target address in the explanation of the read command processing) is a data-migration-complete value or a data-migration-incomplete value (Step S 31 ). In a case where the result of this is that the value of the bit corresponding to the target address is a data-migration-complete value (Step S 32 : Y), the MD-PDKC 100 C reads the target address of the MD-PVOL 112 (Step S 33 , FIG. 8 ( 2 )) and advances the processing to Step S 37 .

Alternatively, in a case where the value of the bit corresponding to the target address is not a data-migration-complete value (Step S 32 : N), the MD-PDKC 100 C reads the target address data from the PVOL 105 in the MS-PDKC 100 A (Steps S 34 through S 36 , FIG. 8 ( 1 )). That is, the MD-PDKC 100 C poses as the host 200 and sends a read command for reading the target address of the MS-PVOL 105 in the MS-PDKC 100 A (Step S 34 ). Upon receiving this read command, the MS-PDKC 100 A reads the target address data of the PVOL 105 in accordance with the read command (Step S 35 ), and sends the read result and read data to the source of the read command (Step S 36 ). The MS-PDKC 100 A perceives the read command source as being the host 200 here, and as such, perceives that the read result and the read data are being sent to the host 200 , but actually the read result and the read data are sent to the MD-PDKC 100 C posing as be the host 200 . Thereafter, the MD-PDKC 100 C receives the read result and the read data sent from the MS-PDKC 100 A and advances the processing to Step S 37 .

In Step S 37 , the MD-PDKC 100 C, posing as the MS-PDKC 100 A, sends the acquired read result and read data to the host 200 , which is the source of the read command, and ends the read command processing. In accordance with this, the host 200 , which sent the read command, acquires the read result and the read data as information that was sent from the MS-PDKC 100 A.

According to the read command processing, the read data migrated to the MD-PVOL 112 is read from the MD-PVOL 112 , and as such can be read faster than when read from the PVOL 105 .

Next, the write command processing in a case where the MD-PDKC 100 C has received a write command from the host 200 with respect to the PVOL 105 part way through a PVOL migration process will be explained.

FIG. 9 is a flowchart of write command processing at the time of a PVOL migration. FIG. 10 is a drawing illustrating the write command processing at the time of the PVOL migration.

The MD-PDKC 100 C, upon receiving a write command and write-target data (write data) for the PVOL 105 from the host 200 , stores the write data in a cache memory of the CMPK 103 , and, in addition, updates the value of a difference bitmap 113 bit corresponding to an address being targeted by the write command (referred to as the target address in the explanation of the write command processing) to a data-migration-incomplete value (Step S 41 , FIG. 10 ( 1 - 1 )).

Next, the MD-PDKC 100 C poses as the host 200 and sends the write command and the write data to be written to the target address of the MS-PVOL 105 in the MS-PDKC 100 A (Step S 42 , FIG. 10 ( 1 - 2 )).

Upon receiving this write command and write data, the MS-PDKC 100 A writes the write data to the target address in the PVOL 105 (Step S 43 ), and sends the write result to the source of the write command (MD-PDKC 100 C) (Step S 44 ). This makes it possible to appropriately store the write data in the PVOL 105 , and to maintain the PVOL 105 as the latest data until the migration of the PVOL 105 has ended. A journal showing update content corresponding to the write command is created in the MS-PDKC 100 A, a sequence number showing the latest sequence is given in the journal, the journal is stored in the PJVOL 108 , and the sequence number showing the latest sequence is stored in the sequence information 109 .

The MD-PDKC 100 C, in a case where, upon receiving the write result sent from the MS-PDKC 100 A, the write result is normal-end, writes the read data stored in the cache memory of the CMPK 103 to the target address in the MD-PVOL 112 (Step S 45 , FIG. 10 ( 1 - 3 )), and updates the value of the difference bitmap 113 bit corresponding to the target address to the data-migration-complete value (Step S 46 , FIG. 10 ( 1 - 4 )). In accordance with this, the write data is also appropriately reflected in the MD-PVOL 112 , doing away with the need to migrate the target address data from the PVOL 105 to the MD-PVOL 112 subsequent thereto.

Thereafter, the MD-PDKC 100 C poses as the MS-PDKC 100 A and sends the acquired write result to the host 200 , which is the source of the write command (Step S 47 ), and ends the write command processing. In accordance with this, the host 200 , which sent the write command, acquires the write result as information that has been sent from the MS-PDKC 100 A.

Next, path addition processing for adding a path between the MD-PDKC 100 C and the SDKC 100 B will be explained. The path addition processing, for example, may be executed when making preparations for a PVOL 105 migration, or prior to the PVOL 105 migration being completed.

FIG. 11 is a flowchart of path addition processing. FIG. 12 is a drawing illustrating the path addition processing.

The administrator connects a path m 1 -m 2 ( 2 ) between the MS-PDKC 100 A and the MD-PDKC 100 C (Step S 51 , FIG. 12 ( 1 )). In this example, virtualization is performed on this path so that the MD-PDKC 100 C appears as the SDKC 100 B to the MS-PDKC 100 A. Specifically, the identification information (port information) of the port 101 in the MD-PDKC 100 C configuring this path is virtualized to the same identification information as the identification information of the port 101 (the port 101 connected to the path m 2 -r) in the SDKC 100 B.

Next, the administrator connects a path m 2 -r between the SDKC 100 B and the MD-PDKC 100 C (Step S 52 , FIG. 12 ( 2 )). In this example, virtualization is performed on this path at this time so that the MD-PDKC 100 C appears as the MS-PDKC 100 A to the SDKC 100 B. Specifically, the identification information (port information) of the port 101 in the MD-PDKC 100 C configuring this path is virtualized to the same identification information as the identification information of the port 101 (port 101 connected to the path m 1 -m 2 ( 2 )) in the MS-PDKC 100 A.

Next, the MS-PDKC 100 A (or, an FC switch that exists between the MS-PDKC 100 A and the SDKC 100 B) adds a path (path m 1 -m 2 ( 2 )) that goes through the MD-PDKC 100 C as the path between the MS-PDKC 100 A and the SDKC 100 B (Step S 53 ). Thereafter, the MD-PDKC 100 C, upon acquiring a command from the SDKC 100 B for the MS-PDKC 100 A via the path m 2 -r, transfers this command to the MS-PDKC 100 A via the path m 1 -m 2 ( 2 ) ( FIG. 12 ( 3 )).

Next, the MS-PDKC 100 A (or, an FC switch that exists between the MS-PDKC 100 A and the SDKC 100 B) deletes the path (path m 1 -r) between the MS-PDKC 100 A and the SDKC 100 B that does not go through the MD-PDKC 100 C (Step S 54 , FIG. 12 ( 4 )). Before deleting the path (path m 1 -r) that does not go through MD-PDKC 100 C, a check may be performed to make sure the command transfer via the path that goes through the MD-PDKC 100 C is operating normally. In accordance with this, a command sent from the SDKC 100 B to the MS-PDKC 100 A always goes through the MD-PDKC 100 C. Therefore, a command (RDJNL) for the PJVOL 108 corresponding to the PVOL 105 can reliably be discerned in the MD-PDKC 100 C.

Next, processing at the completion of data migration, which is executed when a migration of data from the PVOL 105 to the MD-PVOL 112 has been completed, will be explained.

FIG. 13 is a flowchart of processing at the completion of data migration. FIG. 14 is a drawing illustrating the processing at the completion of data migration.

After a migration of data from the PVOL 105 to the MD-PVOL 112 has been completed, the MD-PDKC 100 C suspends the transfer of an SCSI command from the path h-m 2 to the path m 1 -m 2 , and adds a VOL (MD-journal VOL 115 ) of a capacity equal to or greater than the MS-PJVOL 108 to itself (The capacity may also be arbitrarily configured to a capacity that is equal to or less than the MS-PJVOL 108 .) (Step S 61 ). The suspension of the transfer of the SCSI command halts the updating of the PVOL 105 , the PJVOL 108 , and the sequence information 109 in the MS-PDKC 100 A.

Next, the MD-PDKC 100 C, posing as the host 200 , acquires the latest sequence number of the MS-JVOL 108 from the sequence information 109 in the MS-PDKC 100 A (Step S 62 ), and stores the acquired latest sequence number in the sequence information 114 as the latest sequence number of the journal in the MD-JVOL 115 (Step S 63 , FIG. 14 ( 2 )). In a case where the MD-PDKC 100 C has received a write command from the host 200 subsequent thereto, the MD-PDKC 100 C writes the write data to the MD-PVOL 112 target address in the write command, creates a journal from an update number that includes journal data corresponding to the write data and a sequence number (for example, the sequence number in the sequence information 114 +1) based on the sequence number in the sequence information 114 ( FIG. 14 ( 3 )), and updates the sequence information 114 to the latest sequence number. This makes it possible to create, in the MD-PDKC 100 C, a journal having a sequence that is compatible with that of the journal created in the MS-PDKC 100 A.

Next, the MD-PDKC 100 C stores the latest sequence number acquired from the MS-PDKC 100 A as an acquired latest sequence number (Step S 64 ). The acquired latest sequence number shows that the journals up to this sequence number are stored in the JVOL 108 of the MS-PDKC 100 A, and that journals having a larger sequence number are stored in the JVOL 115 of the MD-PDKC 100 C.

Next, the MD-PDKC 100 C performs a configuration for deleting the path (path m 1 -m 2 ) between the MS-PDKC 100 A and the MD-PDKC 100 C on which the MD-PDKC 100 C is posing as the host 200 (Step S 65 , FIG. 14 ( 1 )).

Next, RDJNL command processing, which is executed in a case where the migration-destination storage 100 C has received a RDJNL command for reading a journal from the SDKC 100 B after processing at the completion of a data migration has ended, will be explained. A sequence number specifying the read-target journal (specified sequence number) is associated with the RDJNL command here.

FIG. 15 is a flowchart of RDJNL command processing. FIG. 16 is a drawing illustrating the RDJNL command processing.

The MD-PDKC 100 C, upon receiving a RDJNL command and specified sequence number, determines whether or not the sequence information of the journal corresponding to the RDJNL command from the SDKC 100 B is sequence information guaranteeing that a RDJNL command targeted at a journal prior to the latest sequence information in the MS-PDKC 110 A is not received. Specifically, the MD-PDKC 100 C, upon receiving the RDJNL command and the specified sequence number, determines whether or not the specified sequence number is larger than a number obtained by adding the maximum number of RDJNL commands issued in parallel to the acquired latest sequence number (Step S 71 ). The maximum number of RDJNL commands issued in parallel here shows, in a case where RDJNL commands are capable of being issued in parallel, the maximum value of a difference in sequence numbers for which JNL request and reception sequence shifting is allowed according to asynchronous remote copy specifications.

A case in which the result is that the specified sequence number is larger than the number obtained by adding the maximum number of RDJNL commands issued in parallel to the acquired latest sequence number (Step S 71 : Y) signifies that a RDJNL command for reading a journal stored in the JVOL 108 of the MS-PDKC 100 A does not exist even when the allowable sequence shifting of the specified sequence number in the RDJNL command is taken into account. Consequently, the migration-destination storage 100 C deletes the path between MS-PDKC 100 A and the migration-destination storage 100 C (Step S 72 , FIG. 16 ( 2 )), thereby making it possible for the administrator to dismount the MS-PDKC 100 A (Step S 73 ), and advances the processing to Step S 75 . At this time, the MD-PDKC 100 C can notify the management terminal to the effect that the transfer of the MS-PDKC 100 A JNL has ended (the MS-PDKC 100 A is able to be dismounted).

Alternatively, in a case where the specified sequence number is not larger than the number obtained by adding the maximum number of RDJNL commands issued in parallel to the acquired latest sequence number (Step S 71 : N), an RDJNL command for reading a journal stored in the JVOL 108 of the MS-PDKC 100 A could exist, and as such, the MD-PDKC 100 C advances the processing to Step S 74 .

In Step S 74 , the MD-PDKC 100 C determines whether or not the specified sequence number is larger than the acquired latest sequence number. A case in which the result is that the specified sequence number is larger than the acquired latest sequence number (Step S 74 : Y) signifies that the journal corresponding to the specified sequence number is stored in the JVOL 115 of the MD-PDKC 100 C, and as such, the MD-PDKC 100 C advances the processing to Step S 75 . A case in which the specified sequence number is not larger than the acquired latest sequence number (Step S 74 : N) signifies that the journal corresponding to the specified sequence number is stored in the JVOL 108 of the MS-PDKC 100 A, and as such, the MD-PDKC 100 C advances the processing to Step S 76 .

In Step S 75 , the MD-PDKC 100 C acquires the journal (journal data and update information) corresponding to the specified sequence number from the JVOL 115 ( FIG. 16 ( 1 - 1 )), and advances the processing to Step S 79 .

In Step S 76 , the MD-PDKC 100 C, posing as the SDKC 110 B, sends the RDJNL command and the specified sequence number to the MS-JVOL 108 in the MS-PDKC 100 A. As a result of this, the MS-PDKC 100 B acquires from the MS-JVOL 108 the data in the journal corresponding to the specified sequence number (Step S 77 ), and sends the result of the RDJNL command execution and the acquired journal data to the source of the RDJNL command (Step S 78 ). The MD-PDKC 100 C acquires the RDJNL command execution result and the acquired journal from the MS-PDKC 100 A ( FIG. 16 ( 1 - 2 )) and advances the processing to Step S 79 .

In Step S 79 , the MD-PDKC 100 C, posing as the MS-PDKC 100 A, sends the RDJNL command execution result and the acquired journal to the SDKC 100 B. This makes it possible for the SDKC 100 B to appropriately acquire a required journal and to store this journal in the SJVOL 111 .

Next, the computer system that exists after the MS-PDKC 100 A has been dismounted from the computer system shown in FIG. 16 will be explained.

FIG. 17 is a drawing showing an example of the configuration of the computer system after the MS-PDKC has been dismounted.

As shown in FIG. 17 , the MD-PDKC 100 C poses as the MS-PDKC 100 A with respect to the host 200 in communications via the path h-m 2 . Also, the MD-PDKC 100 C poses as the MS-PDKC 100 A with respect to the SDKC 100 C in communications via the path m 2 -r.

FIG. 18 is a flowchart of read command processing after a data migration has ended.

This read command processing is executed when the MD-PDKC 100 C, which is posing as the MS-PDKC 100 A, has received a read command from the host 200 for the PVOL 105 of the MS-PDKC 100 A after a data migration has ended.

The MD-PDKC 100 C, upon having received a read command specifying the ID of the PVOL 105 from the host 200 , reads data of the MD-PVOL 112 target address in the read command (Step S 81 ), and, posing as the MS-PDKC 100 A, sends the read command execution result and the read data to the host 200 (Step S 82 ). Furthermore, the device information (identification information) for identifying the MD-PVOL 112 may be virtualized to the same device information as that of the PVOL 105 .

FIG. 19 is a flowchart of write command processing after a data migration has ended.

This write command processing is executed when the MD-PDKC 100 C, which is posing as the MS-PDKC 100 A, has received a write command and write data from the host 200 for the PVOL 105 of the MS-PDKC 100 A after a data migration has ended.

The MD-PDKC 100 C, upon having received a write command from the host 200 , writes the write data to the MD-PVOL 112 target address in the write command (Step S 91 ), creates a journal corresponding to the write data, and associates a sequence number based on the sequence number in the sequence information 114 (for example, the sequence number in the sequence information 114 +1) with the journal (Step S 92 ). This makes it possible to create a journal in the MD-PDKC 100 C that is sequentially compatible with the journal created in the MS-PDKC 100 A.

Next, the MD-PDKC 100 C updates the latest sequence number by adding 1 to the sequence number in the sequence information 114 (Step S 93 ). Next, the MD-PDKC 100 C, posing as the MS-PDKC 100 A, sends the write command execution result to the host 200 (Step S 94 ). This makes it possible to appropriately store the write data in the MD-PVOL 112 , and, in addition, to allocate an appropriate sequence number to the journal in accordance with the sequence number in the sequence information 114 .

Next, a computer system related to Example 2 will be explained. The points of difference with Example 1 will be explained for the most part hereinbelow, and explanations of the points in common with Example 1 will either be simplified or omitted.

FIG. 20 is a drawing showing an example of the configuration of a computer system related to Example 2.

The computer system comprises one or more hosts 200 , and one or more DKCs 100 .

The host 200 issues an access command with respect to the PVOL 105 managed by the DKC 100 to the DKC 100 . The host 200 comprises one or more ports 201 . The port 201 is an example of a communication interface device, and is an interface for connecting to a network. Identification information (for example, a world wide name (WWN) or the like) that makes it possible to uniquely identify a port is configured in the port 201 . The host 200 manages information regarding a path to a DKC 100 , this information being associated with the identification information of an access-target VOL (for example, the device number) and the identification information (the port information) of the port 101 in the DKC 100 accessed when accessing the VOL.

A PDKC 100 A is coupled to an MS-SDKC 100 B via a communication network 60 . A MD-SDKC 100 D is installed in a remote site 20 , which is a place that is separated from a local site 10 . The PDKC 100 A is coupled to the MD-SDKC 100 D via the communication network 60 . The MS-SDKC 100 B and the MD-SDKC 100 D are communicably coupled to one another.

The DKCs 100 ( 100 A, 100 B, 100 D), for example, comprise multiple ports 101 , one or more microprocessor packages (MPPKs) 102 , one or more cache memory packages (CMPKs) 103 , an internal network 104 , and a PDEV for configuring one or more VOLs. A VOL is configured using one or more PDEVs. The port 101 , the MPPK 102 , the CMPK 103 , and the VOL-configuring PDEV are communicably coupled via the internal network 104 .

For example, the PDKC 100 A provides a PVOL 105 . The MS-SDKC 100 B provides a MS-SVOL 110 . The MD-SDKC 100 D provides a MD-SVOL 116 .

The port 101 is an example of a communication interface device, and is an interface for connecting to a network. Identification information (for example, a world wide name (WWN) or the like) that makes it possible to uniquely identify a port is configured in the port 101 . Arbitrary identification information (virtual identification information) can be virtually allocated to the port 101 and used in communications.

In this example, for example, the PDKC 100 A comprises a port 101 for coupling to the host 200 , a port 101 for coupling to the MS-SDKC 100 B, and a port 101 for coupling to the MD-SDKC 100 D.

The MS-SDKC 100 B comprises a port 101 for coupling to the host 200 , a port 101 for coupling to the PDKC 100 A, and a port 101 for coupling to the MD-SDKC 100 D.

The MD-SDKC 100 D comprises a port 101 for coupling to the host 200 , a port 101 for coupling to the PDKC 100 A, and a port 101 for coupling to the MS-SDKC 100 B.

The MPPK 102 is a control device comprising either one or multiple processors. The processor executes various processes in accordance with a program. The MPPK 102 may comprise a memory for storing a program executed by the processor, and data that is to be used. In this example, the MPPK 102 of the MD-SDKC 100 D comprises a program for realizing a new function in this example, which will be explained further below. The MPPK 102 in the PDKC 100 A and the MS-SDKC 100 B may comprise existing programs.

The CMPK 103 includes one or more cache memories. The one or more cache memories are a volatile memory and/or a nonvolatile memory. The one or more cache memories may comprise, in addition to a storage area (hereinafter, cache area) for temporarily storing data input/output to/from the PDEV, a storage area (hereinafter, shared area) for storing information that is used by the MPPK 102 processor.

FIG. 21 is a drawing showing an example of the configuration of the computer system in an initial state prior to starting a migration.

The computer system, in the initial state, comprises a host 200 , a PDKC 100 A, and an MS-SDKC 100 B.

The PDKC 100 A comprises a PVOL 105 , and a JVOL 108 for storing a journal (JNL) showing update content with respect to the PVOL 105

The MS-SDKC 100 B stores an MS-SVOL 110 that configures a pair with the PVOL 105 , an SJVOL 111 for storing a journal acquired from the PDKC 100 A, and formalized sequence information 117 for storing a sequence number of a journal that has been formalized (reflected) in the SJVOL 110 (a formalized sequence number).

A path h-m is formed between the host 200 and the PDKC 100 A. For example, an SCSI command such as either a read command or a write command is sent from the host 200 to the PDKC 100 A via the path h-m.

A path m-r 1 is formed between the PDKC 100 A and the migration-source SVOL 100 B. For example, a command (asynchronous remote copy command) is sent from the MS-SDKC 100 B to the PDKC 100 A via the path m-r 1 . As a command that is sent, for example, there is a command (RDJNL command) for reading a journal of the JVOL 108 in the PDKC 100 A.

Next, MD-SDKC connections configuration processing in preparation for migrating an SVOL will be explained.

FIG. 22 is a flowchart of MD-SDKC connection configuration processing. FIG. 23 is a drawing illustrating the MD-SDKC connection configuration processing.

First, the administrator installs the MD-SDKC 100 D for storing the MD-SVOL 116 , for example, at the remote site 20 (Step S 95 , FIG. 23 ( 1 )). At this point in time, the MD-SDKC 100 D is physically coupled to the networks 50 and 60 , and is also physically coupled to the MS-SDKC 100 B.

Next, the administrator connects a path r 1 -r 2 between the MS-SDKC 100 B and the MD-SDKC 100 D (Step S 96 , FIG. 23 ( 2 )). As the method for connecting the path here, there is a method in which the administrator makes the configurations using a terminal of a Service Processor (SVP) coupled to the MD-SDKC 100 D and/or a not-shown management apparatus or the like coupled via a network. There may be cases where the operations and settings performed by the administrator using the SVP or other such terminal are explained giving the “administrator” as the doer of the action without specifying the terminal or the like, but the actual doer of the action may be interpreted as the management apparatus. In this example, virtualization is performed on this path so that the MD-SDKC 100 D appears as the PDKC 100 A to the MS-SDKC 100 B. Specifically, the identification information (port information) of the port 101 in the MD-SDKC 100 D that configures this path is virtualized to the same identification information as the identification information of the port 101 (port 101 connected to the path m-r 2 ) in the PDKC 100 A.

Next, the administrator connects the path m-r 2 between the PDKC 100 A and the MD-SDKC 100 D (Step S 97 , FIG. 23 ( 3 )). In this example, the administrator performs virtualization on this path here so that the MD-SDKC 100 D appears as the MS-SDKC 100 B to the PDKC 100 A. Specifically, the identification information (port information) of the port 101 in the MD-SDKC 100 D that configures this path is virtualized to the same identification information as the identification information of the port 101 (port 101 connected to the path r 1 -r 2 ) in the MS-SDKC 100 B.

Next, PDKC 100 A and the MS-SDKC 100 B (or, an FC switch that exists therebetween) adds paths (path m-r 2 and path r 1 -r 2 ) that go through the MD-SDKC 100 D as paths between the PDKC 100 A and the MS-SDKC 100 B (Step S 98 ). Thereafter, the MD-SDKC 100 D (specifically, the MPPK 102 processor in the MD-SDKC 100 D), upon acquiring a command from the MS-PDKC 100 B for the PDKC 100 A via the path r 1 -r 2 , transfers this command to the PDKC 100 A via the path m-r 2 ( FIG. 23 ( 4 )).

Next, PDKC 100 A and the MS-SDKC 100 B (or, an FC switch that exists therebetween) deletes the path (path m-r 1 ) between the PDKC 100 A and the MS-SDKC 100 B that does not go through the MD-SDKC 100 D (Step S 99 , FIG. 23 ( 5 )). Before deleting the path (path m-r 1 ) that does not go through MD-SDKC 100 D, a check may be performed to make sure the command transfer via the path that goes through the MD-SDKC 100 D is operating normally. In accordance with this, a command (RDJNL command or the like) sent from the MD-SDKC 100 B to the PDKC 100 A always goes through the MD-SDKC 100 D. Therefore, a command can reliably be discerned in the MD-SDKC 100 D.

RDJNL command processing executed in a case where the MD-SDKC 100 D has received an RDJNL command from the MS-SDKC 100 B with respect to the JVOL 108 of the PDKC 100 A after the MD-SDKC connection configuration processing has ended will be explained. Firstly, the RDJNL command processing (first time), which is executed in a case where the MD-SDKC 100 D has initially received an RDJNL command from the MS-SDKC 100 B with respect to the JVOL 108 of the PDKC 100 A after the MD-SDKC configuration setting processing has ended, will be explained.

FIG. 24 is a flowchart of RDJNL command processing (first time) prior to the start of a data migration.

The MD-SDKC 100 D, upon initially receiving an RDJNL command from the MS-SDKC 100 B for the JVOL 108 in the PDKC 100 A, saves the sequence number specified in the received RDJNL command (referred to as the specified sequence number) to its own MPPK 102 memory (Step S 101 ). The specified sequence number saved to memory here is referred to as the saved specified sequence number.

Next, the MD-SDKC 100 D, posing as the MS-SDKC 100 B, sends the RDJNL command and the specified sequence number to the JVOL 108 in the PDKC 100 A (Step S 102 ).

The PDKC 100 A, upon receiving the RDJNL command, reads the journal (update information including journal data and the sequence number) corresponding to the specified sequence number from the JVOL 108 (Step S 103 ), and sends the RDJNL command execution result and journal to the source of the RDJNL command (Step S 104 ). The PDKC 100 A perceives the source of the RDJNL command as being the MS-SDKC 100 B here, and as such, is under the perception that the RDJNL command execution result and journal are being sent to the MS-SDKC 100 B, but actually the RDJNL command execution result and the journal are sent to the MD-SDKC 100 D that is posing as the MS-SDKC 100 B.

Next, the MD-SDKC 100 D, upon receiving the RDJNL command execution result and journal from the PDKC 100 A, poses as the PDKC 100 A and sends the RDJNL command execution result and journal to the MS-SDKC 100 B (Step S 105 ). This makes it possible for the MS-SDKC 100 B to appropriately acquire the journal corresponding to the specified sequence number. The MS-SDKC 100 B stores the acquired journal in the JVOL 111 .

Next, the RDJNL command processing (second time and beyond), which is executed in a case where the MD-SDKC 100 D has received an RDJNL command two or more times from the MS-SDKC 100 B with respect to the JVOL 108 in the PDKC 100 A after the MD-SDKC connection configuration processing has ended, will be explained.

FIG. 25 is a flowchart of RDJNL command processing (second time and beyond) prior to the start of a data migration. FIG. 26 is a drawing illustrating the RDJNL command processing prior to the start of a data migration.

The MD-SDKC 100 D, upon receiving a RDJNL command from the MS-SDKC 100 B for the JVOL 108 in the PDKC 100 A, determines whether or not the specified sequence number corresponding to the received RDJNL command is larger than a value obtained by adding the maximum number of RDJNL commands issued in parallel to the saved specified sequence number (Step S 111 ).

In a case where the result is that the specified sequence number corresponding to the received RDJNL command is larger than the value obtained by adding the maximum number of RDJNL commands issued in parallel to the saved specified sequence number (Step S 111 : Y), the MD-SDKC 100 D, posing as the PDKC 100 A, sends no-journal as the RDJNL command execution result to the MS-SDKC 100 B (Step S 112 , FIG. 26 ( 1 )), and ends the processing.

Alternatively, in a case where the result is that the specified sequence number corresponding to the received RDJNL command is not larger than the value obtained by adding the maximum number of RDJNL commands issued in parallel to the saved specified sequence number (Step S 111 : N), the MD-SDKC 100 D, posing as the MS-SDKC 100 B, sends the RDJNL command and the specified sequence number to the JVOL 108 in the primary storage 100 A (Step S 113 , FIG. 26 ( 2 )).

The PDKC 100 A, upon receiving the RDJNL command, reads the journal corresponding to the specified sequence number from the JVOL 108 (Step S 114 ), and sends the RDJNL command execution result and the journal to the source of the RDJNL command (Step S 115 ). The PDKC 100 A perceives the source of the RDJNL command as being the MS-SDKC 100 B here, and as such, is under the perception that the RDJNL command execution result is being sent to the MS-SDKC 100 B, but actually the RDJNL command execution result and the journal are sent to the MD-SDKC 100 D that is posing as the MS-SDKC 100 B.

Next, the MD-SDKC 100 D, upon receiving the RDJNL command execution result and journal from the PDKC 100 A, poses as the PDKC 100 A and sends the RDJNL command execution result and journal to the MS-SDKC 100 B (Step S 116 ). This makes it possible for the MS-SDKC 100 B to appropriately acquire the journal corresponding to a specified sequence number that is equal to or less than the value obtained by adding the maximum number of RDJNL commands issued in parallel to the saved specified sequence number.

Next, journal formalization processing, formalized sequence number monitoring processing, and migration-destination journal acquisition processing will be explained.

FIG. 27 is a flowchart of formalized sequence number monitoring processing. FIG. 28 is a flowchart of migration-destination journal acquisition processing. FIG. 29 is a drawing illustrating journal formalization processing, formalized sequence number monitoring processing, and migration-destination journal acquisition processing.

The journal formalization processing is for reflecting a journal in the SJVOL 111 in the migration-source SVOL 110 . The MS-SDKC 100 B refers to formalized sequence information 117 , identifies the sequence number of the journal to be formalized next, acquires the journal corresponding to the sequence number from the SJVOL 111 , and on the basis of the journal, writes (updates) the journal data to the SVOL 110 , and updates the formalized sequence number in the formalized sequence information 117 ( FIG. 29 ( 1 )). In accordance with this, update content related to the PVOL 105 is reflected in the SVOL 111 on the basis of the journal.

The formalized sequence number monitoring process is for the MD-SDKC 100 D to monitor the progress of journal formalization in the MS-SDKC 100 B. This formalized sequence number monitoring processing, for example, is executed at fixed intervals.

The MD-SDKC 100 D acquires a formalized sequence number from the MS-SDKC 100 B (Step S 121 , FIG. 29 ( 1 )), and determines whether or not the formalized sequence number is larger than a value obtained by adding the maximum number of RDJNL commands issued in parallel to the saved sequence number (Step S 122 ).

In a case where the formalized sequence number is larger than the value obtained by adding the maximum number of RDJNL commands issued in parallel to the saved sequence number (Step S 122 : Y), the MD-SDKC 100 D starts an SVOL migration process (refer to FIG. 30 ) for migrating data in the MS-SVOL 110 (Step S 123 ), whereas in a case where the formalized sequence number is not larger than a value obtained by adding the maximum number of RDJNL commands issued in parallel to the saved sequence number (Step S 122 : N), ends the processing without doing anything (Step S 124 ).

The migration-destination journal acquisition processing is for the MD-SDKC 100 D to acquire a journal from the PDKC 100 A, and is executed consecutively in order to acquire a journal having a sequence number after the sequence number having the value obtained by adding the maximum number of RDJNL commands issued in parallel to the saved sequence number.

The MD-SDKC 100 D, posing as the MS-SDKC 100 B, sends the RDJNL command and the specified sequence number to the JVOL 108 in the primary storage 100 A (Step S 131 ). Furthermore, the specified sequence number is a sequence number after the sequence number having the value obtained by adding the maximum number of RDJNL commands issued in parallel to the saved sequence number.

The PDKC 100 A, upon receiving the RDJNL command, reads the journal corresponding to the specified sequence number from the JVOL 108 (Step S 132 ), and sends the RDJNL command execution result and the journal to the source of the RDJNL command (Step S 133 ). The MD-SDKC 100 D, upon receiving the RDJNL command execution result and the journal from the PDKC 100 A, stores the journal in a JVOL 119 (Step S 134 , FIG. 29 ( 3 )). This makes it possible for the MD-SDKC 100 D to appropriately store in the JVOL 119 the journal corresponding to the sequence number after the value obtained by adding the maximum number of RDJNL commands issued in parallel to the saved sequence number.

Next, SVOL migration processing and journal data formalization processing during a data migration will be explained.

FIG. 30 is a flowchart of SVOL migration processing. FIG. 31 is a flowchart of journal data formalization processing during a data migration. FIG. 32 is a drawing illustrating the SVOL migration processing and the journal formalization processing during a data migration.

In the SVOL migration process, first of all, the MD-SDKC 100 D adds to itself a VOL (a migration-destination SVOL 116 ) having a capacity of equal to or larger than the SVOL 110 that is the migration destination of the MS-SVOL 110 (Step S 141 , FIG. 32 ( 1 )). The MD-SDKC 100 D manages a difference bitmap 120 here for managing the migration state of the SVOL 110 data in the migration-destination SVOL 116 . The difference bitmap 120 includes bits corresponding to a plurality of areas (blocks) in the migration-destination SVOL 116 , and in accordance with the values of these bits, shows whether or not the SVOL 110 data is being migrated (copied) to these areas.

Next, the MD-SDKC 100 D, posing as the host 200 , defines a path to the SVOL 110 in the MS-SDKC 100 D (Step S 142 ).

Next, the MD-SDKC 100 D updates the values of all the bits in the difference bitmap 120 to values showing that the data migration has not been completed (Step S 143 ).

Then, the MD-SDKC 100 D assumes control and executes the processing of loop (B) (Step S 145 through Step S 149 ) targeted at the addresses of the areas for which the MS-SVOL 110 data migration has yet to be completed, thereby executing the data migration from the MS-SVOL 110 to the migration-destination SVOL 116 ( FIG. 32 ( 2 )). In the explanation of the processing in loop (B), an address targeted for processing will be referred to as a target address.

Specifically, the MD-SDKC 100 D, posing as the host 200 , sends a read command for reading the target address in the MS-SVOL 110 in the MD-SDKC 100 B (Step S 145 ). Upon receiving this read command, the MS-SDKC 100 B reads the data of the SVOL 110 target-address in accordance with the read command (Step S 146 ), and sends the read result and the data that was read (read data) to the source of the read command (Step S 147 ). The MS-SDKC 100 B perceives the read command source as being the host 200 here, and as such, perceives that the read result and the read data are being sent to the host 200 , but actually the read result and the read data are sent to the MD-SDKC 100 D that is posing as the host 200 .

The MD-SDKC 100 D writes the read data received from the MS-SDKC 100 B to the target address of the migration-destination SVOL 116 (Step S 148 ), and updates the bit of the area corresponding to the target address in the difference bitmap 120 to a value showing that data migration has been completed (Step S 149 ).

Then, after executing the loop (B) processing targeted at all the addresses in the area of the MS-SVOL 110 for which data migration has not been completed, the MD-SDKC 100 D ends the processing.

According to this processing, all the data of the SVOL 110 in the MS-SDKC 100 B is migrated to the migration-destination SVOL 116 in the MD-SDKC 100 D.

Next, journal data formalization processing during data migration will be explained. The journal data formalization processing during data migration, for example, is executed after the execution of the SVOL migration process has been started.

The MD-SDKC 100 D reads the journal having the oldest (smallest) sequence number stored in the MD-JVOL 119 (Step S 151 ). Next, the MD-SDKC 100 D acquires the write-target address (target address) inside the journal (in the update information including the journal) (Step S 152 ).

Next, the MD-SDKC 100 D refers to the difference bitmap 120 to determine whether or not the data migration from the SVOL 110 has been completed for the target-address area in the migration-destination SVOL 116 (Step S 153 ). In a case where the result is that the data migration is complete, the MD-SDKC 100 D formalizes the processing-target journal. That is, the MD-SDKC 100 D writes the journal data, which is the update content of the processing-target journal, to the target address in the migration-destination SVOL 116 , and deletes the corresponding journal from the JVOL 119 (Step S 154 , FIG. 32 ( 3 )).

Alternatively, in a case where the result is that the data migration is not complete, the MD-SDKC 100 D poses as the host 200 and sends a read command for reading the target address of the MS-SVOL 110 in the MS-SDKC 100 B (Step S 155 ). Upon receiving this read command, the MS-SDKC 100 B reads the target-address data of the SVOL 110 in accordance with the read command (Step S 156 ), and sends the read result and the read data to the source of the read command (Step S 157 ). The MS-SDKC 100 B perceives the read command source as being the host 200 here, and as such, perceives that the read result and the read data are being sent to the host 200 , but actually the read result and the read data are sent to the MD-SDKC 100 D that is posing as the host 200 .

Next, the MD-SDKC 100 D writes the read data received from the MS-SDKC 100 B to the target address of the migration-destination SVOL 116 (Step S 158 ), updates the difference bitmap 120 bit of the area corresponding to the target address to a value showing that data migration has been completed, and the MD-SDKC 100 D formalizes the processing-target journal data (Step S 154 : FIG. 32 ( 3 )).

Next, processing after the completion of a data migration, which is executed after the SVOL 110 data migration has been completed, will be explained.

FIG. 33 is a flowchart of processing after the completion of a data migration. FIG. 34 is a drawing illustration the deletion of a path after a data migration has been completed.

After the SVOL 110 data migration has been completed, the MD-SDKC 100 D deletes the path (path r 1 -r 2 ) between the MS-SDKC 100 B and the MD-SDKC 100 D (Step S 161 : refer to FIG. 34 ). Thereafter, the administrator can dismount the MS-SDKC 100 B from the computer system (Step S 162 ).

Next, the computer system shown in FIG. 34 after having the MS-SDKC 100 D dismounted will be explained.

FIG. 35 is a drawing illustrating the dismounting of a MS-SDKC.

As shown in FIG. 35 , the MD-SDKC 100 D poses as the MS-SDKC 100 B with respect to the PDKC 100 A in communications via the path m-r 2 . Therefore, the PDKC 100 A is able to communication with the MD-SDKC 100 D without being the least bit aware of the fact that communications are being carried out with the migration-destination source SDKC 100 B the same as before.

A number of examples have been explained hereinabove, but it goes without saying that the present invention is not limited to these examples, and that various changes are possible without departing from the gist thereof.

For example, Example 1 is an example for migrating a PVOL, and Example 2 is an example for migrating an SVOL, but, for example, it is possible to combine Example 1 and Example 2 to migrate the PVOL and the SVOL in parallel.