Backup copying and restoration processing in a storage subsystem Number:7,386,755 from the United States Patent and Trademark Office (PTO) owispatent

Title: Backup copying and restoration processing in a storage subsystem

Abstract: The data up to a point of time whereat failure has occurred will be restored at high speed at a remote site without imposing any burden on a host. The first storage system on the master side processes an I/O request from the host, and as a result of I/O processing to the second storage system on the remote side, transmits the update data. The second storage system retains data received from the first storage system as update log data. The host transmits a command for settling a state of an application to the first storage system as data, and the first storage system transmits the data to the second storage system. The host and the second storage system both retain an identifier corresponding to the command, and relate the identifier to the log data. Thereby, the host designates the identifier at any given time, whereby the second storage system restores the data at any given time.

Patent Number: 7,386,755 Issued on 06/10/2008 to Eguchi,   et al.

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Inventors:	Eguchi; Yoshiaki (Yokohama, JP), Yamamoto; Yasutomo (Sagamihara, JP), Arakawa; Hiroshi (Sagamihara, JP), Hirakawa; Yusuke (Odawara, JP)
Assignee:	Hitachi, Ltd. (Tokyo, JP)
Appl. No.:	10/777,107
Filed:	February 13, 2004

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Foreign Application Priority Data

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Feb 03, 2004 [JP]			2004-026356

Current U.S. Class:	714/6 ; 711/162; 714/15; 714/20
Field of Search:	714/6,15,20 711/161,162 707/202,204

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References Cited [Referenced By]

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U.S. Patent Documents

5263154	November 1993	Eastridge et al.
5485608	January 1996	Lomet et al.
5544347	August 1996	Yanai et al.
5742792	April 1998	Yanai et al.
6044444	March 2000	Ofek
6393537	May 2002	Kern et al.
6393538	May 2002	Murayama
6397229	May 2002	Menon et al.
6460055	October 2002	Midgley et al.
6606694	August 2003	Carteau
6658590	December 2003	Sicola et al.
6671705	December 2003	Duprey et al.
6691245	February 2004	DeKoning
6732123	May 2004	Moore et al.
6732124	May 2004	Koseki et al.
6763436	July 2004	Gabber et al.
6789178	September 2004	Mikkelsen et al.
6981177	December 2005	Beattie
7076620	July 2006	Takeda et al.
7085902	August 2006	Hayardeny et al.
7139927	November 2006	Park et al.
2003/0145179	July 2003	Gabber

Foreign Patent Documents

	2001-216185		Aug., 2001		JP

Primary Examiner: Beausoliel; Robert
Assistant Examiner: Guyton; Philip
Attorney, Agent or Firm: Mattingly, Stanger, Malur & Brundidge, P.C.

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Claims

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What is claimed is:

1. A data restoring method for restoring data stored in a second storage system in a storage subsystem including a first storage system and a second storage system, each of which is connected to a host via a communication channel, in which the second storage system stores a copy of data to be transmitted from the first storage system, wherein the first storage system processes an I/O request from the host, and as a result of I/O processing of the second storage system, transmits updated data according to said I/O request, the second storage system retains data received from the first storage system as update log data, and the host transmits a command for settling a state of an application to the first storage system as data, the first storage system transmits the data to the second storage system, and the host and the second storage system both retain an identifier corresponding to the command, and relate the identifier to the log data whereby the host designates the identifier at any given time to thereby restore data at any given time by the second storage system.

2. The data restoring method according to claim 1, wherein the host issues an I/O instruction of an identifier to the second storage system at a remote site.

3. The data restoring method according to claim 1, wherein the second storage system at a remote site receives the I/O instruction of an identifier of the host, and relates the update log of data to the identifier to store it in a storage unit.

4. A data restoring method for restoring data stored in a second storage system in a storage subsystem including a first storage system and a second storage system, each of which is connected to a host via a communication channel, in which the second storage system stores a copy of data to be transmitted from the first storage system, wherein the first storage system processes an I/O request from the host, and as a result of I/O processing of the second storage system, transmits updated data, the second storage system retains data received from the first storage system as update log data, and the host transmits a command for settling a state of an application to the first storage system as data, the first storage system transmits the data to the second storage system, and the host and the second storage system both retain an identifier corresponding to the command, and relate the identifier to the log data whereby the host designates the identifier at any given time to thereby restore data at any given time by the second storage system, wherein if when restoring data stored in the second storage system to its original state, an identifier which coincides with the identifier which has been transmitted from the host and received is retrieved and the target identifier is searched for, the data is restored in a source storage unit to its original state through the use of data stored in a target storage unit and content of the log data recorded prior to the log data related to the coincided identifier.

5. A data restoring method for restoring data stored in a second storage system in a storage subsystem including a first storage system and a second storage system, each of which is connected to a host via a communication channel, in which the second storage system stores a copy of data to be transmitted from the first storage system, wherein the first storage system processes an I/O request from the host, and as a result of I/O processing of the second storage system, transmits updated data, the second storage system retains data received from the first storage system as update log data, and the host transmits a command for settling a state of an application to the first storage system as data, the first storage system transmits the data to the second storage system, and the host and the second storage system both retain an identifier corresponding to the command, and relate the identifier to the log data whereby the host designates the identifier at any given time to thereby restore data at any given time by the second storage system, wherein on receipt of an acquisition commencement command of log data and a command for suspending pair duplex of the storage unit from the host, the first storage system confirms a storage unit located in the second storage system which is in the pair duplex to suspend the pair duplex.

6. A data restoring method for restoring data stored in a second storage system in a storage subsystem including a first storage system and a second storage system, each of which is connected to a host via a communication channel, in which the second storage system stores a copy of data to be transmitted from the first storage system, wherein the first storage system processes an I/O request from the host, and as a result of I/O processing of the second storage system, transmits updated data, the second storage system retains data received from the first storage system as update log data, and the host transmits a command for settling a state of an application to the first storage system as data, the first storage system transmits the data to the second storage system, and the host and the second storage system both retain an identifier corresponding to the command, and relate the identifier to the log data whereby the host designates the identifier at any given time to thereby restore data at any given time by the second storage system, wherein on receipt of a mark command issued by the host, the second storage system confirms a storage unit which acquires the log data, and sets correspondence of a mark ID and mark data, including a timer value, to the log data acquired.

7. A data processing method for processing data to be stored in a storage unit in a computer system including a storage system equipped with the storage unit connected to a host through a network, wherein the host performs the steps of: requesting the storage system to create and save a copy of data which has been stored in the storage unit; requesting the storage system to record an update portion of data due to processing of the host; and transmitting to the storage system identification information for identifying a state of the computer system at any given time, and the storage system performs the steps of: creating and saving a copy of data of the storage unit in response to a request of the host; saving, when content of the storage unit has been updated, data prior to and subsequent to the update and information indicating a place of update as log data; retaining identification information to be transmitted from the host; and relating the log data to the identification information.

8. The data processing method according to claim 7, wherein when storing the content stored in the storage unit to a state at any given time, the host designates state identification information to transmit a request for restoring the data to the storage system, and the storage system discriminates the identification information received and restores the data through the use of a copy of the data and the log data.

9. The data processing method according to claim 8, wherein the identification information that the host and the storage system have in common is managed by the storage system by relating the identification information to update history, and data stored in the storage unit up to update history indicated by specific identification information is restored in response to an instruction from the host.

10. The data processing method according to claim 8, wherein the log data includes at least an entry for a mark flag indicating whether or not it is specific identification information, an entry for identification information of a log, an entry for a timer value indicating a time period during which the log has been acquired, and an entry which becomes a data area, and when the mark flag indicates the specific identification information, the entry of the data area is defined as at least an entry of mark identification information and an entry for a timer value indicating a time period during which the mark has been imparted.

11. The data processing method according to claim 10, wherein on executing a program, when a file is closed, or when the file is saved, the host generates a specific command for relating the log data to the identification information to transmit it to the storage system, and the storage system executes the command, sets the mark flag to a specific state, and retains, in the storage unit, log data in which mark identification information and time values have been stored in the entry.

12. A storage subsystem including a first storage system and a second storage system, each of which is connected to a host via a communication channel, for storing, in the second storage system, a copy of data stored in the first storage system, the first storage system comprising: a storage unit having a plurality of logical storage units; a cache memory for temporarily storing data to be inputted into or outputted from the storage unit; a memory for storing at least management information concerning the logical storage unit, management information for defining a configuration of pair duplex between the first storage system and the second storage system and a program for processing a command from the host; and a processor for executing the program, the second storage system comprising: a plurality of logical storage units, of which a certain logical storage unit stores a copy of data to be stored in a logical storage unit of the first storage system constituting a pair, and another logical storage unit comprises: a storage unit to be allocated in order to store log data generated by the first storage system; a cache memory for temporarily storing data to be inputted into or outputted from the storage unit; a memory for storing at least management information concerning the logical storage unit, management information for defining a configuration of pair duplex between the first storage system and the second storage system, management information of a log and a program for processing a command from the host; and a processor for executing the program, wherein when content of a certain logical storage unit of the first storage system has been updated, the data thus updated and information indicating a place of update are transmitted to the second storage system as log data and stored in the logical storage unit, and management information for bringing identification information transmitted from the host into correspondence with the log data is stored in the memory.

13. The data storage subsystem according to claim 12, wherein when the log data stored in the logical storage unit in the second storage system is restored to a state at any given time, the second storage system receives a request for restoring data transmitted from the host, and restores the log data stored in the logical storage unit by referring to the management information stored in the memory concerning the identification information.

14. The data storage subsystem according to claim 12, wherein the memory of the first storage system and the memory of the second storage system have: a storage management information table for registering correspondence between an address of the storage unit which the host is capable of identifying and a logical address within the storage unit; a storage management information table for registering correspondence among a logical address within the storage unit, an address concerning a RAID group in which the logical storage unit has been arranged, and an address concerning a disk for forming the RAID group; a volume configuration information table for registering volume configuration information correspondingly to a number of the logical storage unit; and a pair management information table for registering correspondence between a number of the logical storage unit within the first storage system for constituting a pair and a number of the logical storage unit within the second storage system.

15. The data storage subsystem according to claim 14, wherein at least the second storage system has: a log volume group information table which registers management information concerning a logical storage unit within the log volume group for each log volume group; a log ID management information table for bringing a log ID to be imparted when the log data is stored in the logical storage unit into correspondence to a timer value when the log data has been acquired to register as management information; and a mark ID management information table for bringing identification information to be imparted when the log data is stored in the logical storage unit, which has been transmitted from the host, into correspondence to a timer value when the log data is stored to register as management information.

16. The data storage subsystem according to claim 12, wherein in the first storage system, the command processing program processes a command to be transmitted from the host, and when the command is a mark command, creates log data and performs processing for imparting the identification information, and in the case of an I/O processing command, the command processing program determines a hit or a miss-hit of the cache memory, writes write data in the cache memory, or reads out read data from the cache memory.

17. The data storage subsystem according to claim 12, wherein on receipt of the mark command issued by the host, the second storage system confirms a storage unit which acquires the log data, and sets correspondence between the log data thus acquired and mark ID and mark data including timer values.

18. A storage system for storing, in a second storage system, a copy of data to be stored in a first storage system to be connected to a host via a communication channel, having: a plurality of logical storage units, of which a certain logical storage unit stores a copy of data to be stored in a logical storage unit of the first storage system constituting a pair, and another logical storage unit comprises: a storage unit to be allocated in order to store log data generated by the first storage system; a cache memory for temporarily storing data to be inputted into or outputted from the storage unit; a memory for storing at least management information concerning the logical storage unit, management information for defining a configuration of pair duplex between the first storage system and the second storage system, management information of a log and a program for processing a command from the host; and a processor for executing the program, wherein when content of a certain logical storage unit of the first storage system has been updated, the data thus updated and information indicating a place of update are transmitted to the second storage system as log data and stored in the logical storage unit, and management information for bringing identification information transmitted from the host into correspondence with the log data is stored in the memory.

19. The storage system according to claim 18, wherein when the log data stored in the logical storage unit is restored to a state at any given time, the second storage system receives a request for restoring data transmitted from the host, and restores the log data stored in the logical storage unit by referring to the management information stored in the memory concerning the identification information.

20. A storage subsystem including a first storage system and a second storage system, each of which is connected to a host via a communication channel, for storing, in the second storage system, a copy of data stored in the first storage system, the first storage system comprising: a storage unit having a plurality of logical storage units; a cache memory for temporarily storing data to be inputted into or outputted from the storage unit; a memory for storing at least management information concerning the logical storage unit, management information for defining a configuration of pair duplex between the first storage system and the second storage system and a program for processing a command from the host; and a processor for executing the program, wherein the command processing program processes a command to be transmitted from the host, and when the command is a mark command, creates log data and performs processing for imparting identification information, and in the case of an I/O processing command, the command processing program determines a hit or a miss-hit of the cache memory, writes write data in the cache memory, or reads out read data from the cache memory, the second storage system comprising: a plurality of logical storage units, of which a certain logical storage unit stores a copy of data to be stored in a logical storage unit of the first storage system constituting a pair, and another logical storage unit comprises: a storage unit to be allocated in order to store log data generated by the first storage system; a cache memory for temporarily storing data to be inputted into or outputted from the storage unit; a memory for storing at least management information concerning the logical storage unit, management information for defining a configuration of pair duplex between the first storage system and the second storage system, management information of a log and a program for processing a command from the host; and a processor for executing the program, wherein when content of a certain logical storage unit of the first storage system has been updated, the data thus updated and information indicating place of update are transmitted to the second storage system as log data and stored in the logical storage unit, and management information for bringing identification information transmitted from the host into correspondence with the log data is stored in the memory, on receipt of an acquisition commencement command of log data and a command for suspending the pair duplex of the storage unit from the host, the first storage system confirms a storage unit located in the second storage system which is in the pair duplex to suspend the pair duplex, when the log data stored in the logical storage unit in the second storage system is restored to a state at any given time, the second storage system receives a request for restoring data transmitted from the host, and restores the log data stored in the logical storage unit by referring to the management information stored in the memory concerning the identification information.

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Description

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a storage subsystem, and more particularly to remote copying of a storage subsystem for acquiring a write I/O log and a method of restoring a log during a disaster.

2. Description of the Prior Arts

A computer system has become commercially practical in which a computer and a storage system are connected together through a network, and data to be processed by the computer is transmitted and received via the network and is stored in the storage system. In online processing and batch processing that are to be carried out by the computer system, there may enter a situation in which these processing abnormally terminates by program bugs, failure of the storage system and the like to cause contradictions in the data stored in the storage system. Also, the data stored in the storage system may be erased by an artificial mistake.

In order to recover data of the computer system which has entered such a state, there is known a data recovery technique by way of backup and restoration of data as one of techniques for resuming processing suspended halfway by getting rid of the data contradiction, or doing over the processing suspended halfway again.

As conventional technique concerning the backup and restoration, in, for example, U.S. Pat. No. 5,263,154 (Patent Reference 1), there has been disclosed a technique in which data stored in the storage system at a point of time designated by the user is reproduced (hereinafter, referred to as "backup of data") on a magnetic tape without stopping input and output (hereinafter, referred to as "I/O") of data from a host connected to the storage system, and through the use of the data thus reproduced (hereinafter, referred to as "backup data"), the data is recovered (hereinafter, referred to as "restore").

Also, in Japanese Published Unexamined Patent Application No. 2001-216185 (Patent Reference 2), in order to shorten time required to restore the data, there has been disclosed a technique in which information in a place where the data has been updated is retained as difference information after backup of the data is carried out, and when data stored in the storage system is restored with the backup data, only a portion of the backup data shown by the difference information is used to restore the data.

Also, in U.S. Pat. No. 5,544,347 (Patent Reference 3) and U.S. Pat. No. 5,742,792 (Patent Reference 4), there has been disclosed a technique for copying data by a remote storage system independently of the host. According to this technique, it is possible to make a copy of a business volume within the storage system which has been made by the host at a certain business site on a volume within the storage system at a remote site. For that reason, in consideration of a case where the business site suffers from a natural disaster and terrorism, the computer system causes an failure and the business cannot be continued, it is possible to prepare data for restoring the business at a remote site.

SUMMARY OF THE INVENTION

In the restoration processing described in Patent Reference 1, when reading out backup data from a magnetic tape, a portion which has not been updated from a point of time whereat the backup data has been acquired (that is, a portion in which the data of the storage system coincides with the content of data of the magnetic tape) is also read out from the magnetic tape, and is written in the storage system. It is wasteful to transfer such data, and it takes longer time to restore.

In the technique disclosed in Patent Reference 2, time to restore becomes short by an amount corresponding to readout of overlapped data which does not occur as compared with the technique of Patent Reference 1. As regards data which has been updated during a period of time from a time at which backup of data is carried out to a time at which the storage system develops a failure, however, the data cannot be restored by either technique. When an attempt is made to restore data which has been updated after backup of data is carried out, it is necessary for the host side to manage the content of update of the data and the like by the log and the like. For this reason, load on the host is great and it takes a long time to process.

Also, in Patent References 3 and 4, there has been disclosed the technique for creating data for restoring the business at a remote site on the assumption that the business site suffers from a disaster, and the computer system develops a failure and the business cannot be continued, but no consideration has been given to a measure against danger of copying at a remote site concerning unfair writing which is caused by writing during the disaster.

It is an object of the present invention to provide a computer system capable of restoring data at any given time prior to occurrence of the failure at high speed.

It is an object of the present invention to provide a storage system for restoring data at a remote site without imposing a burden on the host when restoring the data stored in the storage system.

The present invention is preferably realized by a storage subsystem including a first storage system and a second storage system, each of which is connected to a host via a communication channel, in which the second storage system stores a copy of data to be transmitted from the first storage system. In this storage subsystem, the first storage system processes an I/O request from the host, and as a result of the I/O processing to the second storage system, transmits updated data, and the second storage system retains data received from the first storage system as update log data. The host transmits a command for settling a state of an application to the first storage system as data, and the first storage system transmits the data to the second storage system. The host and the second storage system both retain an identifier corresponding to the command, and relate the identifier to the log data. When restoring the data to its original state, the host designates the identifier at any given time, whereby the second storage system restores data at any given time.

In a preferred example, the host issues an I/O instruction of state identification information to the second storage system at a remote site. The second storage system at the remote site receives the I/O instruction of the state identification information of the host, and relates the updated log of data to the identification information to store it in a storage unit.

According to the present invention, when restoring the data stored in the storage system, it is possible to restore data to its predetermined state at a remote site without imposing any burden on the host within a short time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing structure of a computer system according to one embodiment;

FIG. 2 is a block diagram showing structure of storage systems 3 and 4;

FIG. 3 is a block diagram showing structure of a host 1;

FIG. 4 is a view showing structure of a table of storage management information 115, 150;

FIG. 5 is a view showing structure of a table of storage configuration information 116, 151;

FIG. 6 is a view showing structure of a table of volume configuration information 117, 152;

FIG. 7 is a view showing structure of a table of pair management information 118, 153;

FIG. 8 is a view showing structure of a table of log volume group information 110;

FIG. 9 is a view showing structure of a table of volume pool configuration information 156;

FIG. 10 is a view showing structure of a table of log volume quantity consumed pool management information 155;

FIG. 11 is a view showing structure of a table of log ID management information 157;

FIG. 12 is a view showing structure of a table of mark ID management information 158;

FIG. 13 is a view showing a format of log data;

FIG. 14 is a view showing a flowchart to be used for explaining a processing operation of creating a pair;

FIG. 15 is a view showing a flowchart to be used for explaining a command processing operation while a pair is being created;

FIG. 16 is a view showing a flowchart for a log acquisition commencement processing operation on the master side;

FIG. 17 is a view showing a flowchart for a log acquisition commencement processing operation on a remote side;

FIG. 18A is a view showing a flowchart (host side) of a mark command processing operation;

FIG. 18B is a view showing a flowchart (storage system 3 side) of a mark command processing operation;

FIG. 19 is a view showing a flowchart for command processing while the log is being acquired at a remote site;

FIG. 20 is a view showing a flowchart for a log data creating operation at a remote site;

FIG. 21 is a view showing a flowchart for an excessive log volume capacity processing operation;

FIG. 22 is a view showing a flowchart for take over processing; and

FIG. 23 is a view showing a flowchart for recovery processing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, with reference to the drawings, the description will be made of one embodiment of the present invention.

FIG. 1 is a block diagram showing a computer system according to one embodiment.

This computer system includes a first host computer 1 (hereinafter, referred to as host 1), a second host computer 2 (hereinafter, referred to as host 2), a first storage system 3 (hereinafter, referred to as storage system 3 simply) to be connected to the host 1 via a communication channel 5, a second storage system 4 (hereinafter, referred to as storage system 4 simply) to be connected to the host 2 via a communication channel 7 and to be connected to the storage system 3 via a communication channel 6, a first storage system management unit 8 to be connected to the storage system 3 via a communication channel 11, a second storage systemanagement unit (hereinafter, referred to as management unit) 9 to be connected to the storage system 4 via a communication channel 12, and a computer system management unit 13 to be connected to these structural units via a communication channel 10. The storage system 3, 4 is constructed by including such storage units 21, 22, 23 as, for example, a disk device and a disk array, and their control units. In this case, the second system side is positioned as a remote site.

The host 1 and the host 2 are computers such as personal computers, work stations and main frames. In the host 1, there are carried out operating systems (OS) corresponding to type of the computer, and various application programs (AP) corresponding to various business and use applications such as, for example, data base (DB) programs. In this respect, in this example, one each of the host 1 and host 2 is shown for the sake of simplicity, but a plurality of hosts 1 or hosts 2 to be connected to the communication channel 5 or the communication channel 7 may be provided.

The host 1 performs the predetermined processing in the computer system. In other words, the host 1 communicates commands and data required for I/O processing concerning information processing with the storage system 3 through the use of the communication channel 5, requests the storage system 3 to write the data created and changed in the host 1, and also requests to read data required for computer processing.

The storage system 3 receives commands and data to be transmitted via the communication channel 5 to conduct predetermined processing, and carries out a predetermined response to the host 1. The storage system 3 and the storage system 4 communicate commands and data between them via the communication channel 6.

Although the storage system 4 is actually the same in structure as the storage system 3, they are different in FIG. 1 in that the storage system 4 has a plurality of storage units 22 and 23. Although it will be described in detail later, of those two storage units, one storage unit 22 is used as a mirror of the storage unit 21, and the other is used for log data storage.

The management unit 8 is a computer for managing a failure, maintenance, structure, performance information and the like of the storage system 3 in addition to setting of the storage system 3. Similarly, the management unit 9 is a computer for setting the storage system 4 and also managing a failure, maintenance, structure, performance information and the like of the storage system 4. When, for example, the manager of the computer system sets such a logical storage unit as, for example, volume on the storage system 3 and the storage system 4, when setting a storage area for backing up the data, or when setting a pair of storage area when reproducing data, these management units 8 and 9 are used.

When maintaining and managing the storage system 3, setting a physical storage unit which the storage system 3 has, and setting the host 1 to be connected to the storage system 3, the system manager inputs contents that should be set on the management unit 8. The contents that the system manager has inputted to the management unit 8 are transmitted to the storage system 3 and the host 1 via the communication channel 11, 10.

The computer system management unit 13 is used to maintain and manage the entire computer system, and is normally operated and utilized by the system engineer.

The communication channels 5 and 7 are used for the host 1 and the host 2 to transmit a request for processing I/O and the like to the storage system 3 and the storage system 4 respectively. The communication channel 6 is used to transmit the request for processing I/O and the like between the storage system 3 and the storage system 4. For the communication channels 5, 6 and 7, there are used optical cable, copper wire and the like. Examples of communication protocols for use with these communication channels 5, 6 and 7 include, for example, Ethernet, FDDI, fiber channel, SCSI, Infiniband, TCP/IP, iSCSI and the like.

Communication channels 11 and 12 are used for the storage system 3 or 4 to transfer management information such as its own failure, maintenance, structure, and performance between those management units 8 and 9.

The communication channel 10 is used to transfer a command when the host 1, 2 acquires management information from the management units 8, 9, and to transmit management information of failure, maintenance, structure, performance and the like of the storage system 3, 4 to the host 1 from the management units 8, 9. Cable and communication protocol for use with the communication channels 10, 11, 12 may be the same as or different from the communication channels 5, 6, 7.

FIG. 2 is a view showing the structure of the storage systems 3, 4.

The storage system 3 is made up of a storage system control unit 101 and a storage unit 21, and a storage area of the storage unit 21 is provided to input and output from the host 1. In other words, the storage system 3 stores data and programs that the host 1 uses, receives an I/O processing request from the host 1, performs processing corresponding to the I/O processing request, and transmits the result to a predetermined host 1.

The storage control unit 101 has a storage adapter 108 to be connected to the storage unit 21, a processor 105 for executing a predetermined program, a program to be executed by the processor 105, a non-volatile control memory 107 in which information required in an operation of the program such as setting information, structural information and the like of the storage system 3 is stored, a network adapter 102 for connecting this storage system 3 to the communication channel 11, a host adapter 103 for connecting to the communication channel 5, and a remote I/O adapter 104 for connecting to the communication channel 6, and performs processing of the I/O request from the host 1 and control of the storage unit 21.

The storage unit 21 is made up of a plurality of logical storage units 109, each of which is referred to as "volume", and in each of the respective storage units 109, there is stored data for an user. The storage unit 21 is preferably configured to have RAID (Redundant Arrays of Inexpensive Disks) configuration having redundancy. As a storage medium of the storage unit 21, there are used media such as a silicon disk, an optical disk, an optical magnetic disk or a hard disk which are constructed by a magnetic disk and a nonvolatile semiconductor memory which are, for example, electrically nonvolatile storage media.

In this respect, a plurality of storage control units 101 may be present in the storage system 3. Also, in order to secure the redundancy of the storage system 3, it is advisable to redundant-construct a circuit for supplying power supply to each component element within the storage control unit 101, a circuit for transmitting and receiving data between each component element within the storage control unit 101, a cache memory 106, the non-volatile control memory 107, the storage adapter 108 and the like by making each of them duplex.

In order to control processing within the storage system 3, the non-volatile memory 107 stores therein each program of a command processing program 111, a remote I/O processing program 112, a copy manager program 113, a pair management program 114, a network processing program 119, a storage I/O processing program 121, and a system configuration management program 122. The non-volatile memory 107 stores an exclusive processing pit for accessing to an area in which there is the cache memory 106, and information indicating correspondence relationship between the storage unit 109 and the cache memory 107 therein for the I/O processing. In this respect, if there exist a plurality of storage control units 101 and processors 105, it is possible to have the non-volatile control memory 107 in common.

The cache memory 106 temporarily stores data to be transferred from the host 1 to the storage system 3 or data to be transferred to the host 1 from the storage system 3.

A local area network 120 causes the storage control unit 101, the cache memory 106 and the storage unit 109 to connect together to one another. The local area network 120 may be, for example, of a shared bus type configuration, and also of a star type and other network configuration.

The storage control unit 101 controls processing to be explained below by executing a program stored in the non-volatile memory 107 by the processor 104.

On receipt of the I/O processing request from the host 1 by the host adapter 102, the command processing program 111 analyzes content of the I/O processing request received. In accordance with the analysis result, the content of the I/O processing request executes readout I/O (hereinafter, referred to as "read I/O") of data, write I/O (hereinafter, referred to as "write I/O") processing request of data and the like. In the case of the write I/O processing request, the storage control unit 101 performs response processing to the write I/O processing request from the host 1, such as response processing whether or not it is in a state capable of receiving data to be actually transferred from the host 1, and further writes data for update (hereinafter, referred to as "write data") to be transferred in a place designated of the cache memory 106 or the storage unit 109. In the case of the read I/O processing request, the storage control unit 101 reads out data (hereinafter, referred to as "read data") corresponding to the read I/O processing request from a place designated of the cache memory 106 or the storage unit 109 to transfer to the host 1. Also, when other processing, for example, input and output I/F with the host is SCSI and an inquiry command (command for instructing device search) is received, the host I/O processing program controls an operation corresponding to the content of processing to be requested by the command.

The system configuration management program 122 is a program to be executed when the storage control unit 101 manages the storage system 3, and prepares, sets, changes, and deletes storage unit management information 115, 116. By executing the system configuration management program 122, the storage control unit 101 performs definition of the storage unit 109 to be inputted from the management unit 8, setting of the storage unit 109 which becomes a pair target for backup/snap shot, registration of information targeted for log storing and the like. In this case, the storage unit management information 115, 116 retains mapping information indicating correspondence relationship between address within the storage system and address for performing input to and output from the host storage unit, and information concerning the pair 118.

The storage I/O processing program 121 is a program to be executed when the storage control unit 101 performs read and write processing to the cache memory 106 or the storage unit 109. On executing a read-write I/O processing request, the system configuration management program 122 is executed to check the storage unit 109 at the access target for structure, it is calculated to which address in the storage unit 109 address at a place where read or write data which is designated by the read-write I/O processing request should be read out or stored corresponds, and on the basis of the calculation result, access to the storage unit 109 is performed.

The pair management program 114 is a program for managing a pair of a master volume (hereinafter, referred to as "M-VOL") and a remote volume (hereinafter, referred to as "R-VOL"). By executing the pair management program 114, the storage control unit 101 processes pair creation (Pair Create), pair suspension (Pair Suspend), pair resumption, and pair deletion (Pair Delete) concerning a storage unit ("R-VOL") 139 within the storage unit 22 which is located within the remote storage system 4 in which a reproduction of data stored in a certain storage unit 109 ("M-VOL") and M-VOL 109 is stored in accordance with an instruction from the host 1.

In this respect, it is also possible to set a plurality of R-VOLs against one M-VOL for creating. Also, it is also possible to set and create a R-VOL which makes a pair with a new M-VOL with the R-VOL as a new M-VOL.

The pair management information 118 registers information indicating whether or not a certain M-VOL109 is in a pair state (Pair Duplex), in a pair created state (Pair Create) and in a pair suspended state (Pair Suspend).

By executing the copy manager program 113, the storage control unit 101 copies data on the R-VOL in order from the head address of the M-VOL139 during pair creation, whereby data stored in the M-VOL is backed up in the R-VOL. Further, the storage control unit 101 gives an instruction to the remote I/Os processing program 112 to copy data in a portion having a difference from M-VOL to R-VOL by referring to difference information 123, and to conversely copy data having a difference from R-VOL to M-VOL by referring to the difference information 123. In this case, the difference information 123 is a bit map provided correspondingly to the storage area of the storage unit 109 in order to prevent copy data of M-VOL and R-VOL from disagreeing with each other, and when data of the storage area of the storage unit 109 is rewritten after remote-copied, a bit flag will be set correspondingly to the area thus updated for management.

Also, the pair management program 114 restores data of the storage unit 109 designated in accordance with a restore request from the host 1. In this respect, details of the restore processing will be described later.

In the foregoing, the description has been made of the structure of the storage system 3 on the master site side.

On the other hand, the storage system 4 on the remote site side also has the similar program and information basically. Major points of difference will be described. The storage unit 22 stores copy data of the storage unit 21 on the master site side while the storage unit 23 stores log data that occurred on the master site side. The log data that occurred on the master site side may be stored in the storage unit on the master side as a matter of course, and in the example shown in FIG. 2, the structure is arranged such that the log data is transmitted to the remote storage system 4 via the communication channel 6 to store in a logic storage unit 140 within the storage unit 23. In this respect, the structure of logic storage unit (volume) 139, 140 within the storage unit 22, 23 is similar.

As regards information to be stored in the non-volatile memory 137, each program of a command processing program 142, a remote I/O processing program 143, a copy manager program 144, a pair management program 145, a network processing program 159, a storage unit I/O processing program 162, and a system configuration management program 163, storage unit management information 150, 151, volume configuration information 152, pair management information 153, difference information 164 and the like are similar to the program or information on the master site side corresponding thereto.

In order to perform a characteristic operation of storing log data and its management information in the storage unit 23 at a remote site and restoring the log data on the basis of the management information, however, in the non-volatile memory 137, there are stored a log volume group management program 146, a quantity consumed management program 147, a log ID management program 148, a Mark ID management program 149, log volume group configuration information 154, log volume group quantity consumed management information 155, volume pool configuration information 156, log ID management information 157, and Mark ID management information 158. Functions and meaning of these programs and information will be explained in order hereinafter.

Next, with reference to FIG. 3, the description will be made of the structure of the host 1.

The host 1 will be exemplified for description, and the structure of the host 2 is actually similar to the host 1.

The host 1 is configured to have a processor 201 for executing a predetermined program; a memory 202 to be used for storing OS, AP and data to be used by the AP; a disk unit 207 in which OS, AP and data to be used by the AP are stored; an I/O adapter 205 for connecting to a communication channel 5; a network adapter 206 for connecting to a communication channel 10; a removable storage drive unit 209 for controlling readout and the like of data from a portable storage medium such as a floppy disk; a display unit 203 such as a liquid crystal display; an input device 204 such as a keyboard and a mouse; and a local I/O network 208 to be used for transferring data of OS and AP and control data by connecting these configuration units together.

Examples of the portable storage media for use with the removable storage drive unit 209 include optical disks such as CD-ROM, CD-R, CD-RW, DVD and MO, magnetic disks such as optical magnetic disks, hard disks and floppy disks, and the like. In this respect, each program to be explained below is installed in the disk unit 207 of the host 1 by being read out from the portable storage medium via the removable storage drive unit 209 or by passing through the network 4 or 5. In this respect, the host 1 may have a plurality of configuration units such as the processor 201 in order to secure the redundancy.

Next, the description will be made of an example of a program to be executed by the host 1.

These programs 210 are stored in the disk unit 207 of the host 1 or the memory 202, and are executed by the processor 201.

The host 1 has AP 233 for operating under OS230, and data base management software (hereinafter, referred to as "DBMS") 232. The DBMS232 accesses the storage system 3 via the OS230, a file system (FS) 231, a volume manager (VM) 235 and the like. Also, the DBMS232 communicates I/O processing of transaction processing and the like with another AP 233 which the user uses. With the objective of improving the information processing performance, the processor 201 executes information processing through the use of a memory 202 of the host 1.

Also, information having correlation between a plurality of logical storage units which the host 1 performs input and output is retained as log volume group management information 248. Also, the pair management information 249 retains M-VOL which is a logical storage unit in which the host 1 performs input and output, and management information of R-VOL which makes a pair therewith. A pair operating program 247 performs pair operation, pair creation (Pair Create), pair suspension (Pair Suspend), pair resumption and pair deletion (Pair Delete) on the storage system 3. A log operating program 246 performs a log operation such as log acquisition commencement and log acquisition completion. A pair management program 245 monitors a pair state of the storage system 3 and monitors for a failure. A capacity management program 244 retains the capacity of the storage system 3 as information, and calculates the total capacity of the logical storage unit to be contained in the log volume group. A mark processing program 243 is called after commitment processing when AP 233 or DBMS232 saves or closes a file, creates mark data and writes on the storage system 3. A mark ID management program 242 creates mark data through the use of a timer and mark ID information 241 when a mark processing program 243 writes mark data. Mark ID information 241 is management information against the log ID, and is made up of mark ID and log time information.

Next, with reference to FIGS. 4 and 5, the description will be made of storage unit management information 115, 150 and storage management information 116, 151. In this respect, symbols on the storage system 3 side will be referred to for the description.

In FIG. 4, storage unit management information 115 is a table having an entry 301 for creating an address concerning a storage unit 21 to be provided for the host 1, and an entry 302 for creating a logical address for identifying storage units 21 in the storage system 3 in a unified way.

The entry 301 has an entry 303 for creating an identifier of a storage unit to be provided for a host computer and an entry 304 for creating its internal address. Also, the entry 302 has an identifier 305 of the logical storage unit 109 within the storage unit 21 for identifying the storage units in a unified way in the storage system 3, and an entry 306 for creating its internal address.

In FIG. 5, storage management information 116 is a table having an entry 401 for registering a logical address for identifying storage units 21 within the storage system 3 in a unified way, an entry 402 for registering an address concerning RAID Group, and an entry 403 for registering an address concerning a disk which constitute the RAID Group.

Further, the entry 401 has an entry 404 for registering a logical storage number which identifies, in a unified way, logical storage units 109 within the storage system 3, and an entry 405 for registering internal addresses corresponding to the storage units. The entry 402 has an entry 406 for registering a RAID Group number for identifying, in a unified way within the storage system 3, RAID Group in which there are arranged logical storage units to be identified by the logical storage number which identifies, in a unified way, logical storage units 109 within the storage system 3, and an entry 407 for registering an address corresponding in virtual space in which the RAID Group has been handled as one storage area. Also, the entry 403 has an entry 407 for registering a disk number for identifying, in a unified way within the storage system 3, disks which form the RAID Group, and an entry 408 in which disk internal addresses are registered.

Next, with reference to FIG. 6, the description will be made of volume configuration information 117, 152 shown in FIG. 2. In this respect, since the volume configuration information 152 is also similar, symbols on the storage system 1 side will be referred to for description.

The volume configuration information 117 is a table for registering information concerning configuration of the volume in the storage system 3. In the entry 501, there are registered logical storage numbers which handle logical storage units within the storage system 3 in a unified way. On the entry 502, there are registered host types. In other words, there is registered information indicating which storage unit capable of being recognized OS of a host for performing input/output to the logical storage unit emulates, such as "OPEN" indicating a storage unit capable of recognizing OS of an open line system, and "3990" indicating a storage unit capable of recognizing OS of a main frame system.

In the entry 503, there is registered pass definition information indicating whether or not it is related to an I/O port so as to allow the host 1 to perform input/output. If, for example, the I/O network is FC, there will be registered information concerning linking the logical storage unit with a port of FC.

The entry 504 is used to register a state of the logical storage unit, and there is registered, for example, information indicating a normal state (NORMAL) in which the logical storage unit develops no failure, but input/output can be performed, or information indicating a state (BLOCKED) in which input/output cannot be performed because of a failure and the like. Further, as failure information, there is registered information indicating whether or not the logical storage unit has developed some failure or other. In this case, the failure includes physical failures of physical storage units mainly constituting the logical storage unit and logical failures when the manager has consciously set the storage system to a blocked state.

The entry 505 is used to register reserved information, and there is registered, for example, information indicating whether or not the logical storage unit is in a reserved state in order to store R-VOL or log data. The logical storage unit in which reserved information has been registered cannot be newly allocated to other use applications, and, for example, as a logical storage unit for business use.

When the logical storage unit 109 forms a pair, a pair number is registered on the entry 506 for registering pair information, and when acquiring log data within the storage unit, a log volume group number is registered on the entry 507 for registering log volume group numbers. If there is effective information, for example, a log volume number on the entry 506, there will be registered information indicating whether or not the logical storage unit is a target of log acquisition, that is, a target of journal mode. Also, on the entry 508, there is registered capacity of the logical storage unit 109.

Next, with reference to FIG. 7, the description will be made of pair management information 118, 153. In this respect, reference numerals on the pair management information 118 side will be referred to.

The pair management information 118 is a table for registering identifiers of the original and duplicate logical storage units constituting the pair. In other words, a pair number is registered on the entry 601. On the entry 602, there is registered a unified logical storage unit (M-VOL) number within the storage system 3 on the master side for forming the pair. On the entry 603, there is registered information for identifying the logical storage unit (R-VOL) located in the storage system 4 on a remote side which forms M-VOL and the pair. For example, on the entry 603, there are registered an identifier of an I/O port to be connected through the communication channel 6 and a unified storage number within the storage system 4 accessible from this port. On the entry 604, there is registered information indicating states of pair, such as, for example, pair state, pair being created, pair being suspended, and pair being recreated.

Next, with reference to the drawings of FIG. 8 and thereafter, the description will be made of the structure of a table peculiar to the storage system 4 on the