JPH11327803A - Data multiplexing control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To duplex data in an extension logic unit without receiving logic volume information of a duplex object from a host device at the time of controlling a plurality of logic volumes as one extension logic unit. SOLUTION: A command analysis part 81 realized by the micro processor 8 of a regular disk controller 2 judges whether a processing in a pair formation processing of regular/auxiliary disk devices is for extended LU or not by an automatic extended LU management information table 83. It issues a special command to an auxiliary disk controller 5, reads auxiliary side extended LU information and stores it in the self-extended LU management information table 83 and an auxiliary extended LU management information table 84. An extended LU state after a pair is formed is managed by the self-extended LU management information table 83 and a pair state is continued if needed even if several logic volumes forming extended LU are in a blocked state in accordance with designation at the time of forming the pair.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an external storage controller that receives a write command from a higher-level device and writes data to an external storage device under another external storage controller that holds the same data. In particular, the present invention relates to an information processing system that realizes data multiplexing, and configures a partner logical unit in volume control in which the capacity of a logical unit is expanded by controlling a plurality of logical volumes as one logical unit from a host device. The present invention relates to a data multiplexing control technique for a logical unit that realizes duplex control without receiving logical volume information from a higher-level device, and a technique that is effective when applied to an external storage control device or the like using the same.

[0002]

2. Description of the Related Art As a method of holding data used by a host device in a plurality of external storage devices, primary and secondary external storage devices holding the same data are provided under different external storage controllers, and the external storage controllers are connected to each other. The primary external storage controller issues a write command received by the primary external storage controller to the secondary external storage controller so that data between the primary and secondary external storage devices can be transferred. A common method is to achieve agreement. On the other hand, by combining multiple logical volumes into one logical unit as an external storage device in an open system, the capacity supported by the external storage device system in the host operating system or application with a limited number of logical units is maximized. The method used is limited.

[0003]

Here, for example, a logical unit of one logical unit = 1 logical volume (hereinafter, referred to as a logical unit)
In the case where the logical volume is extended to a plurality of logical volumes, a plurality of logical volumes are collectively defined as one LU in the configuration information setting of the external storage control device, so that the LU extended in the external storage control device (hereinafter referred to as LU) is defined. , Extended LU) and the logical volumes constituting the extended LU can be operated in association with each other.

However, in this case, the upper-level device issues a request for duplication to the primary external storage controller in units of extended LUs.
In the primary external storage controller that does not hold logical volume information related to the primary and secondary external storage controllers, pairing between logical volumes between the primary and secondary external storage controllers cannot be realized.

An object of the present invention is to realize data multiplexing between storage subsystems in units of extended logical units when controlling a plurality of logical volumes as one extended logical unit in each storage subsystem. It is to provide a data multiplexing technology that can be used.

Another object of the present invention is to provide an extended logic between storage subsystems when controlling a plurality of logical volumes as one extended logical unit in each of the storage subsystems operating under various host devices. It is an object of the present invention to provide a data multiplexing technique capable of realizing data multiplexing in units.

Another object of the present invention is to control a plurality of logical volumes as one extended logical unit and perform data multiplexing in units of extended logical units. An object of the present invention is to provide a data multiplexing technique capable of realizing various correspondences between logical volumes.

Another object of the present invention is to control a plurality of logical volumes as one extended logical unit and perform data multiplexing in units of extended logical units. An object of the present invention is to provide a data multiplexing technique capable of continuing data multiplexing even when logical volumes are in a closed state.

Another object of the present invention is to control a plurality of logical volumes as one extended logical unit and perform data multiplexing in units of extended logical units. Is to provide a data multiplexing technique capable of continuing data multiplexing irrespective of the state of the logical volume constituting the data multiplexing.

[0010]

According to the present invention, a first storage subsystem connected to a host device and a second storage subsystem connected to the first storage subsystem have a first storage subsystem. A plurality of first logical volumes in the subsystem are controlled as one first extended logical unit from the host device, and the first extended logical unit is used as a unit to write data between the first and second storage subsystems. When performing multiplexing, the first storage subsystem configures a second extended logical unit in the second storage subsystem corresponding to the first extended logical unit from the second storage subsystem side. The multiplexing of the write data is realized by reading the configuration information of the second logical volume.

More specifically, the first (positive side) and the second
When the (secondary) storage subsystem has a configuration including a storage control device and a storage device operating under the storage control device, the storage subsystem includes the following units.

That is, when the primary external storage control device receives the pair formation request from the higher-level device, the primary external storage control device obtains, from the secondary external storage control device, the logical volume information constituting the secondary extended LU, Means for determining the pairing target of the primary and secondary logical volumes according to the logical volume information constituting each of the extended LUs, means for executing and managing the pair forming process for the determined pairing target,
Means for providing the information indicating the pair status to the higher-level device, and automatically recovering the logical volume status of some of the logical volumes constituting the extended LU in the blocked status upon the release of the blocking factor Means for performing

The method of determining the pairing of the primary and secondary logical volumes is as follows: Pairing method: A method of combining volumes of the same capacity one by one in order, or Pairing method: Volumes are set so that the primary volume capacity <the secondary volume capacity. A method of one-to-one combination, a method of pairing: a method in which the external storage controller automatically determines an n-to-m combination (combination of several volumes or a combination that satisfies the conditions) with volumes having different volume capacities, It is realized by.

As a method of providing the information indicating the status of the extended LU to the higher-level device, when the status of the logical volume constituting the extended LU does not match even one pair due to an operation or a failure, the status as the extended LU is also changed. Display according to the logical volume status or configure the extended LU 1
When the state of a logical volume pair is in a closed state due to an operation or a failure, the other logical volumes constituting the extended LU are operated in a normal state, and the extended LU state is a normal state in which some logical volumes are in a blocked state. Display according to the state of the logical volume is performed by the display method.

In a pair formation request from a host device in an open system, primary and secondary LU information is specified. For example, in the case of a disk controller, the SCSI port / target ID / LU
# Is given. The primary disk control device that has received the pair formation request can recognize the logical volume configuring the primary extended LU from the primary extended LU information. For the secondary logical volume, a sense-related special command to which the secondary extended LU information is added is issued to the secondary disk controller, and the logical volume information configuring the extended LU is received from the secondary disk controller. , The pairs of primary and secondary logical volumes can be sequentially assigned.

When determining the primary and secondary logical volumes to be paired, it is also possible to allocate an optimal secondary logical volume to each primary logical volume based on the volume type and volume capacity included in the logical volume information.

Next, by displaying an appropriate extended LU status according to the status of the logical volume, it is possible to confirm that the operation has been performed normally or to prompt an appropriate recovery operation. The detailed information display for each logical volume can be separately displayed.

Further, by individually managing the logical volumes constituting the extended LU, the extended LU pairs in which some of the logical volume pairs constituting the LU are in a closed state in response to a request can be set to the other steady state. An extension L
By writing the update data for the U configuration logical volume to the secondary logical volume, it is possible to continue the steady state as the extended LU.

In addition, when the blocking cause is released, the pair status is periodically monitored in the primary disk control device, so that the host device does not issue a re-pair formation request when the blocking cause is released. It is also possible to restore the extended LU pair state to a steady state by automatically performing re-pair formation. The re-pair formation here means that, in the closed state, only the updated data is written from the primary logical volume to the secondary logical volume from the difference information of the primary and secondary logical volume update histories held in the disk controller. This also includes a method of re-matching the primary and secondary volumes.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a conceptual diagram showing an example of the configuration of a data processing system in which a data multiplexing control method according to an embodiment of the present invention is implemented. FIG. It is the conceptual diagram illustrated in detail.

The data processing system of the present embodiment includes a primary open host 1 and a secondary open host 4 which is a backup system. Further, as examples of the storage subsystem, a plurality of primary disk devices 3 and secondary disk devices 6, a SCSI port 7 and a SCSI port 11,
Microprocessor 8 and microprocessor 12,
Buffer memory 9 and buffer memory 13, DKC channel port 10 and DKC channel port 14
Are included in the primary disk controller 2 and the secondary disk controller 5, respectively. Each of the primary open host 1 and the secondary open host 4 is connected to each of the primary disk controller 2 and the secondary disk controller 5 by an interface cable 15. The primary disk controller 2 and the secondary disk controller 5 are connected by an interface cable 16. The interface cable 16 may be any information communication network.

The primary disk controller 2 (similarly to the secondary disk controller 5), as shown in FIG.
In addition to the buffer memory 9 and the DKC-to-DKC channel port 10, a command analysis unit 81, a secondary disk control device issuing command determination unit 82, a self-extended LU management information table 83, a secondary extended LU management information table 84, and a secondary disk control device command issuance Unit 85, extended LU status display function determining unit 86,
including. Each unit of the command analysis unit 81 to the extended LU status display function determination unit 86 is a functional block realized by a microprogram executed by the microprocessor 8 incorporated in the primary disk control device 2.

In this embodiment, the primary and secondary extended LUs are used as one means for realizing pair formation in extended LU units.
Means for determining the pair target of the primary and secondary disk devices along with the pair formation and managing the pair status include a command analysis unit 81,
The sub disk controller issuing command determining unit 82, the secondary disk controller command issuing unit 85, and the extended LU status display function determining unit 86. The pair statuses of the primary and secondary disk devices and the extended LU management information are stored in the primary extended LU management information table 83 and the secondary extended LU management information table 84 on the primary side.

As exemplified in FIG. 3, as an example, the self-expanded LU management information table 83 of the primary disk control device 2 includes a device number 83a corresponding to a logical volume (logical DEV) in the primary disk device 3, a device type 83b, LU information 8 such as the unit name of the extended logical unit
3c, device state 83d, and the corresponding device number 8 of the logical volume in the secondary disk device 6
3e, device type 83f, LU information 83g, and device status 83h are stored.

As shown in FIG. 4, the secondary extended LU management information table 84 of the primary disk control device 2 includes a device number 84a, a device type 84b, and LU information corresponding to a logical volume in the secondary disk device 6. 8
4c and information such as allocation information 84d in which a device number 83a corresponding to the logical volume of the corresponding primary disk device 3 is stored.

As exemplified in FIG. 5, as an example, the self-expanded LU management information table 90 of the secondary disk control device 5 includes a device number 90a, a device type 90b, LU information 90c such as the unit name of the unit, a device status 90d, and a device number 90e corresponding to the logical volume in the primary disk device 3, a device type 90f, LU information 90g, a device status 90h,
Information is stored.

The device status 83d of each logical volume,
SX: Simplex for 83h, 90d, and 90h
(Unpaired), DP: Duplex Pendin
g (during copying), DC: Duplex Complete
e (copied: pairing completed), SD: Suspend
(Closed), either is set.

Hereinafter, an example of the operation of the present embodiment will be described with reference to FIG.
This will be described with reference to the flowchart of FIG.

When the primary open host 1 issues a pair formation command to the primary disk controller 2 by designating an extended LU (step 101), the command analyzer 81 determines whether the pairing command is for the extended LU. This is performed by referring to the LU information 83c of the self-extended LU management information table 83 (see FIG. 3). If the command is for the extended LU, the sub-disk control device issuing command is issued from the sub-extended LU information received by the command analysis unit 81. The determination unit 82 creates a secondary disk information request command that constitutes the secondary extended LU, and the secondary disk control device command issuing unit 85 sends it as a sense special command via the DKC channel port 10 and the interface cable 16. Issued to the inter-DKC channel port 14 of the secondary disk control device 5. . Upon receiving the command, the secondary disk control device 5 recognizes that the command is a special command in the secondary command analysis unit, and determines the secondary extended LU management information table 90 (from the primary disk controller, the secondary extended LU management information table). Logical volume information (for example, device number 90a to device status 90)
d, etc.) as sense data to the primary disk controller 2 (step 102).

The primary disk control device 2 that has received the secondary logical volume information determines whether a pair can be formed (step 103). If the pair cannot be formed, the primary disk control device 2 responds to the primary open host 1 that the pair cannot be formed. (Step 10
8). If a pair can be formed, it is stored in each entry of the device number 84a, the device type 84b, and the LU information 84c of the primary side secondary extended LU management information table 84, and the secondary logical volume is sequentially stored in the primary logical volume. Assignment (set the device number 83a of the primary logical volume in the assignment information 84d), and when this assignment is completed, register the target secondary volume in the primary self-extended LU management information table 83 (device number 83e, device type 83f, LU information 83g is set).

In the case of an extended LU including volumes having different storage capacities, the secondary extended LU management information table 84 on the primary side is searched in descending order of the capacity of the primary logical volume, and the secondary logical LU having the same or smaller capacity is searched. It is assigned to a volume and registered in the self-extended LU management information table 83 in the same manner (see FIG. 3).

Thereafter, the primary disk control device 2
In accordance with the pair information of the U management information table 83, the data of the primary disk device 3 is written to the secondary disk device 6, and the corresponding extended L of the primary disk device 3 and the secondary disk device 6 are written.
Data duplication between the constituent logical volumes is performed between the U and the statuses of the device status 83d and the device status 83h are set (Step 104, Step 10).
5, Step 106, Step 107).

After the completion of the data duplication, the write request received by the command analysis unit 81 is similarly sent to the corresponding secondary disk control unit 5 to maintain the data duplication state. It should be noted that the status of the primary and secondary volumes is determined, and information such as a transient status is stored in the own extended LU management information table 8 for each volume constituting the extended LU.
3 are registered in the device state 83d and the device state 83h (see FIG. 3).

In the example of FIG. 3, the LU information 83c in the primary disk device 3 is indicated by "A", and the logical volume (D
For the extended logical unit “A” composed of EV # 0, storage capacity of 8 Gbytes, logical volume (DEV # 1, storage capacity of 4 Gbytes), and logical volume (DEV # 2, storage capacity of 2 Gbytes) A logical volume (DEV # M, storage capacity of 8 Gbytes) and a logical volume (DEV # M-2, storage capacity of 4) on the secondary disk device 6 side.
G), and an extended logical unit “E” consisting of a logical volume (DEV # M-1, storage capacity of 2 Gbytes) is allocated (in the case of the pairing method).

The LU information 83c in the primary disk device 3 is indicated by "B", and the logical volume (DEV #
3, storage capacity is 4 GB), logical volume (DEV
The logical volume (DEV # 0, the storage capacity is 5 GB) and the logical volume (DEV # 1) on the secondary disk device 6 side for the extended logical unit “B” composed of # 4, storage capacity of 4 GB. , A storage capacity of 5 Gbytes) is assigned (in the case of the pairing method).

The LU information 83c in the primary disk device 3 is indicated by "C" and the logical volume (DEV #
5, storage capacity is 6 GB), logical volume (DEV
The logical volume (DEV # 2, the storage capacity is 4 GB) and the logical volume (DEV # 3) on the secondary disk device 6 side are provided for the extended logical unit “C” composed of # 6, storage capacity of 6 GB. , An extended logical unit “J” consisting of a logical volume (DEV # 4, a storage capacity of 4 Gbytes) and a storage volume of 4 Gbytes (in the case of a pairing method).

In the pairing of the extended logical unit "C" and the extended logical unit "J", since the number of logical volumes differs from each other, the correspondence between the storage areas of the logical volumes is managed, for example, in cylinder units. For this reason,
In this example, the cylinder information for each logical volume is set to the device type 83b and the device type 83f.

FIG. 6 shows that the primary open host 1
6 shows an example of a screen for presenting a volume status to a system administrator.

Regarding the display of the pair status, when an extended LU status display request command from the primary open host 1 is received, the extended LU status display function determination unit 86
The state (device state) of each volume constituting the extended LU is searched from the management information table 83, and the lowest level state is displayed to the host according to the following volume state levels (weighting). For example,
In the case of the pair of the extended LUs “A” and “E” in FIG. 3, “DP” is displayed as the state of the primary extended LU “A” in FIG.

Pair established state (DD)> Pair established (DP)> Pair closed state (SD)> Pair release state (SX) Also, a threshold value is set for the volume state level by designation at the time of pair formation, and extended LU If the logical volume pair constituting the logical LU pair is equal to or larger than the threshold value, for example, even when the logical volume pair is in the closed state, the status of the extended LU is displayed as the pair established state, The logical volume on the primary side is held as differential data, and the update data for the logical volume in the pair-established state is written to the secondary logical volume, thereby continuing the steady state as the extended LU. For example, in the case of the pair of the extended LUs “B” and “F” in FIG. 3, the device status of some logical volumes constituting the secondary extended LU “F” is “SD”. Nevertheless, in FIG. 6, “DC” is displayed as the state of “B”, which is the extended LU on the primary side.

In the specification at the time of pair formation, when the cause of the blockage of the pair is released, or by referring to the self-expanded LU management information table 83 at regular intervals in the primary disk control device 2, By periodically issuing a re-pair formation request, the pair status is automatically restored to the pair established status.

That is, as exemplified in FIG. 8, the primary disk controller 2 monitors the arrival of a command from the primary open host 1 (step 201), and when a command is received, the command is Execute (Step 202).

If no command has been received, it is checked at a predetermined timer period whether or not a pair status check has been triggered (step 203). If not, the process returns to command reception.

In the case of a pair status check trigger, the own extended LU management information table 83 is checked (step 20).
4), the presence or absence of the pair of the blocked state "SD" is checked (step 205), and if there is, the current state of the secondary logical volume that has been closed is inquired to the secondary disk controller 5 (step 205). 206, step 207).

If the block status of the logical volume has been released, the status of the logical volume is changed to "DP", and a copy start instruction of the differential data is issued (step 208). Is completed (step 209), the state of the logical volume is changed to “DC”, and the pair restoration state is completed (step 210).

As described above, according to the data multiplexing control method of the present embodiment, each of the primary disk controller 2 and the secondary disk controller 5 When each of the plurality of logical volumes is controlled as one extended LU, without receiving the logical volume configuration information on the side of the secondary disk device 6 to be subjected to data duplication from the primary open host 1, the extended LUs are controlled in units of extended LUs. The data duplication between the primary disk controller 2 and the secondary disk controller 5 can be achieved.

The correspondence between the logical volumes constituting the extended LU can be determined by combining the volumes of the same capacity one by one (pairing method) in a one-to-one manner such that the primary volume capacity is smaller than the secondary volume capacity. (Pairing method), n-by-m combinations with volumes having different volume capacities (pairing method), and the like.

Further, the extended L
Even if some logical volumes forming U are in a closed state, it is feasible to continue the duplication.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say, there is.

For example, in the above-described embodiment, a case has been described in which data is duplicated by associating one primary disk control device with one secondary disk control device. Data multiplexing may be performed in association with the above-mentioned secondary disk control device.

[0052]

According to the data multiplexing control method of the present invention, when a plurality of logical volumes are controlled as one extended logical unit in each storage subsystem,
An effect is obtained that data multiplexing between storage subsystems in units of extended logical units can be realized.

In a case where a plurality of logical volumes are controlled as one extended logical unit in each of the storage subsystems operating under various host devices, data multiplexing between the storage subsystems in units of extended logical units. Thus, the effect that the realization can be realized can be obtained.

When a plurality of logical volumes are controlled as one extended logical unit and data multiplexing is performed in units of extended logical units, various types of logical volumes among the plurality of extended logical units to be multiplexed are used. The effect that association can be realized is obtained.

Further, when controlling a plurality of logical volumes as one extended logical unit and performing data multiplexing in units of extended logical units, the logical volumes between the plurality of extended logical units to be multiplexed are in a closed state. , The effect that data multiplexing can be continued can be obtained.

When a plurality of logical volumes are controlled as one extended logical unit and data multiplexing is performed in units of extended logical units, when data multiplexing is performed in units of extended logical units, the logical volumes constituting each of the plurality of extended logical units to be multiplexed. Data multiplexing can be continued regardless of the state,
The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating an example of a configuration of a data processing system in which a data multiplexing control method according to an embodiment of the present invention is implemented.

FIG. 2 is a conceptual diagram illustrating a part of the part extracted in more detail.

FIG. 3 is a conceptual diagram showing an example of control information used in a data multiplexing control method according to an embodiment of the present invention.

FIG. 4 is a conceptual diagram showing an example of control information used in a data multiplexing control method according to an embodiment of the present invention.

FIG. 5 is a conceptual diagram showing an example of control information used in a data multiplexing control method according to an embodiment of the present invention.

FIG. 6 is an explanatory diagram showing an example of a screen for presenting a volume status to a system administrator in a higher-level device in a data multiplexing control method according to an embodiment of the present invention.

FIG. 7 is a flowchart illustrating an example of an operation of a data multiplexing control method according to an embodiment of the present invention.

FIG. 8 is a flowchart showing an example of the operation of the data multiplexing control method according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Primary open host, 2 ... Primary disk controller (1st storage subsystem), 3 ... Primary disk device (1st storage subsystem), 4 ... Secondary open host, 5 ... Secondary disk controller ( 2nd storage subsystem), 6 ... secondary disk device (2nd storage subsystem), 7 ... SCS
I port, 8 microprocessor, 9 buffer memory, 10 DKC channel port, 11 SCSI port, 12 microprocessor, 13 buffer memory, 14 DKC channel port, 15 interface cable, 16 interface Cable, 81 ...
Command analysis unit, 82: Secondary disk control device issued command determination unit, 83: Self-extended LU management information table, 83a
... Device number, 83b ... Device type, 83c ... L
U information, 83d: device status, 83e: device number, 83f: device type, 83g: LU information, 83
h: Device status, 84: Secondary extended LU management information table, 84a: Device number, 84b: Device type,
84c: LU information, 84d: Assignment information, 85: Secondary disk control device command issuing unit, 86: Extended LU status display function determining unit, 90: Own extended LU management information table, 9
0a: Device number, 90b: Device type, 90c
... LU information, 90d ... device status, 90e ... device number, 90f ... device type, 90g ... LU information, 9
0h: Device state.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuhide Sano, 2880 Kozu, Odawara-shi, Kanagawa, Japan Storage Systems Division, Hitachi, Ltd. Hitachi Software Engineering Co., Ltd. In-house (72) Inventor Jin Shiozawa 2880 Kozu, Odawara-shi, Kanagawa Prefecture Storage Systems Division, Hitachi, Ltd.

Claims (5)

[Claims] 1. A storage system comprising: a first storage subsystem connected to a higher-level device; and a second storage subsystem connected to the first storage subsystem, wherein the first storage subsystem comprises: Write the write data received from the host device into its own storage subsystem and
In the data processing system that multiplexes the write data in the first and second storage subsystems by also writing to the storage subsystem of the first storage subsystem, the plurality of first logical volumes in the first storage subsystem are When controlling as one first extended logical unit from the host device and multiplexing the write data between first and second storage subsystems in units of the first extended logical unit, One storage subsystem is a second logical volume configuring a second extended logical unit in the second storage subsystem corresponding to the first extended logical unit from the second storage subsystem. A data multiplexing control method, wherein the multiplexing of the write data is realized by reading the configuration information of (1). 2. The data multiplexing control method according to claim 1, wherein each of the plurality of first and second logical volumes constituting each of the first and second extended logical units has the same storage. A first method for associating ones having a capacity with one-to-one, each of the plurality of first and second logical volumes constituting each of the first and second extended logical units, to the first method A second method for making a one-to-one correspondence so that the storage capacity of a logical volume is smaller than the storage capacity of the second logical volume, comprising different numbers of the first logical volume and the second logical volume. The first extended logical unit and the second extended logical unit are different from each other in that the storage capacity of the first extended logical unit is larger than the storage capacity of the second extended logical unit. A data multiplexing control method, wherein the first and second extended logical units are associated with each other by any one of the following three methods: 3. The data multiplexing control method according to claim 1, wherein the state of each of said first and second logical volumes constituting said first and second extended logical units is multiplexed by data copying. Are completed, a pair is being established in which data copying is not completed and multiplexing is not completed, a blocked state where access to the second logical volume is not possible, and a pair released state where multiplexing is not performed. When managing, the statuses of the first and second extended logical units are displayed in response to a higher-level device according to the weighting of the statuses of the first and second logical volumes. Data multiplexing control method. 4. The data multiplexing control method according to claim 3, wherein even when some of the second logical volumes constituting the second extended logical unit are in a closed state, the data is not transmitted to the higher-level device. Receiving the write data by continuously responding to the pair establishment state of the first extended logical unit corresponding to the second extended logical unit, and holding the write data after the closed state as differential data. Data multiplexing control method. 5. The data multiplexing control method according to claim 4, wherein when a blocking factor of said second logical volume in said second extended logical unit is released, said second logical volume of said first extended logical unit is removed. From the first logical volume to the second
Automatically copying the difference data to the second logical volume of the extended logical unit of the
Data multiplexing control method for recovering multiplexing between the second extended logical unit and the second extended logical unit.