Abstract:
It is an object to eliminate possibilities in which newest backup data cannot be created owing to overwriting of data update records when performing backup using a duplicating system. The data backup system, including an active system as a computer system of a backup source and a standby system as a computer system of a backup destination, is provided in such that a communication settings judging section is provided in the standby system for actively changing settings of a data communicating section for transferring data update records to thereby prevent overwriting of portions among data update records that are necessary for creating newest backup data.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   The present application claims priority from Japanese Patent Application No. JP 2004-61584 filed on Mar. 5, 2004, the content of which is hereby incorporated by reference into this application. 
   TECHNICAL FIELD OF THE INVENTION 
   The present invention relates to a data backup system and a backup method of data. 
   BACKGROUND OF THE INVENTION 
   Data backup systems employing two computer systems are widely employed. Backup of data means that the data identical to those of one computer system are created and stored in another computer system. A computer system of a backup source is referred to as an active system and a computer system of a backup destination as a standby system. Further, data that are stored in the standby system are referred to as backup data. Such backup of data using a duplicating system is described in, for instance, CHRISTOS A. POLYZOIS, HECTOR GARCIA-MOLINA, “Evaluation of Remote Backup Algorithms for Transaction-Processing Systems”, ACM Transactions on Database Systems, Vol. 19, No. 3, September 1994, Pages 423–449 (hereinafter referred to as Reference 1). 
   A known method for backup using a duplicating system is a log transfer method. The log transfer method is a method in which data update records of an active system are transferred to a standby system whereupon backup data are created in the standby system. In the log transfer method, data of the active system and backup data of the standby system are made identical at the stage of starting backup. After start of backup, data update records of the active system are transferred to the standby system. In the standby system, backup data are updated using the transferred data update records. Results of studies in which the log transfer method is applied to a database system are described in Reference 1. 
   In general, computer systems have external storage devices, and data of computer systems are stored in the external storage devices. The external storage devices mean, for example, hard disk drives or disk arrays, which are magnetic storage devices. 
   Some of the external storage devices have copy functions for copying data between two devices. For instance, external storage device SANRISE9980V which is a product of Hitachi, Ltd. has HITACHI True Copy Function. The HITACHI True Copy Function is a function of transferring data via a network and of copying data of one SANRISE9980V to another SANRISE9980V. In case data are added to the external storage device of the copy source, the same data are added to the external storage device of the copy destination as well. When data of the external storage device of the copy source are overwritten, the data on the external storage device are also overwritten. Storage areas of the external storage devices are used upon dividing them into logical areas referred to as volumes, and whether copy functions are to be used or not can be set for each of the volumes. 
   Backup using the log transfer method is performed by using copy functions of external storage devices. The structure is as follows. At the stage of starting backup, data of the active system and backup data of the standby system are made identical. Data update records that have been added to the external storage device of the active system are copied to the external storage device of the standby system by using the copy functions to the volumes storing therein data update records. In the standby system, newest backup data are created using the copied data update records. 
   SUMMARY OF THE INVENTION 
   When performing backup through the log transfer method by using copy functions of the external storage device, it would conventionally happen that no newest backup data could be created. This occurred due to the fact that data update records were overwritten prior to creating newest backup data in the standby system. Newest backup data cannot be created in the standby system since overwritten data cannot be referred to. 
   The present invention aims to solve the problems of preventing a case in which no newest backup data can be created through overwriting of data update records when backup through log transfer method is to be performed by using copy functions of the external storage device. 
   The data backup system according to the present invention includes at least a standby system, which is a computer system of a backup destination. The standby system includes a data communicating section that receives data update records and stores them in an external storage device; a data updating duplicating section that refers to the data update records to create backup data; a communication settings judging section that judges changes in settings of the data communicating section; and a communication settings changing section that changes settings of the data communicating section. 
   The external storage device is divided into a plurality of storage areas; orders of usage are defined for the storage areas for storing the data update records; and the communication settings judging section judges settings of the data communicating section on the orders of usage of the storage areas that have been referred to by the data updating duplicating section. 
   There are also cases in which functions of preventing overwriting of data update records are provided for both of an active system, which is a computer system of a backup source and a standby system, which is a computer system of a backup destination. The active system includes a data updating section that stores data and data update records in an external storage device; a data communicating section that sends the data update records; a communication settings judging section that judges settings of the data communicating section; and a communication settings changing section that changes settings of the data communicating section. 
   The standby system includes a data communicating section that receives the data update records and stores them in an external storage device; a data updating duplicating section that refers to the data update records to create backup data; and a communication settings changing section that changes settings of the data communicating section. 
   The external storage device of the active system and the external storage device of the standby system are divided into a plurality of storage areas; orders of usage are defined for the storage areas for storing the data update records; the communication settings judging section of the active system judges settings of the data communicating section on the orders of usage of the storage areas that have been referred to by the data updating section; and the communication settings judging section of the standby system judges settings of the receiving section on the orders of usage of the storage areas that have been referred to by the data updating duplicating section. 
   By providing communication settings judging sections and by changing settings of the data communicating section in conjunction with the data updating duplicating section in the present invention, overwriting of portions necessary for creating newest backup data from among data update records is prevented. Cases in which newest backup data cannot be created due to overwriting of data update records can thus be avoided. 

   
     BRIEF DESCRIPTIONS OF THE DRAWINGS 
       FIG. 1  is a block diagram of a data backup system using a duplicating system. 
       FIG. 2  is a view illustrating an example of settings for dividing storage areas of an external storage device. 
       FIG. 3  is a view illustrating an example for settings of a communicating section setting table. 
       FIG. 4  is a functional diagram of a backup system according to a first embodiment. 
       FIG. 5  is a flowchart illustrating an order of operations of respective sections according to the first embodiment. 
       FIG. 6  is a flowchart illustrating operations of a data updating section. 
       FIG. 7  is a flowchart illustrating operations of a data communicating section. 
       FIG. 8  is a flowchart illustrating operations of a data updating duplicating section. 
       FIG. 9  is a flowchart illustrating operations of a communication settings judging section. 
       FIG. 10  is a functional diagram of a backup system according to a second embodiment. 
       FIG. 11  is a flowchart illustrating an order of operations of respective sections according to the second embodiment. 
       FIG. 12  is a flowchart illustrating operations of a data updating section according to the second embodiment. 
       FIG. 13  is a flowchart illustrating operations of a data settings judging section according to the second embodiment. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   There are two embodiments of the present invention, namely one in which the communication settings judging section is provided in the standby system and another in which the communication settings judging sections are provided in the active system and in the standby system. The two embodiments of the present invention will now be explained with reference to the drawings. 
     FIG. 1  is a block diagram of a data backup system using a duplicating system. A backup system using a duplicating system includes two computer systems. A computer system of a backup source is referred to as an active system  101  while a computer system on a backup destination is referred to as a standby system  102 . The active system  101  includes a server  103  of the active system and an external storage device  104  of the active system. The standby system  102  includes a server  105  of the standby system and an external storage device  106  of the standby system. The external storage device  104  of the active system and the external storage device  106  of the standby system are connected via a network  107 . 
     FIG. 2  is a view illustrating an example of settings for dividing storage areas of the external storage device  104  of the active system and the external storage device  106  of the standby system. The external storage devices are used upon being divided into storage areas referred to as volumes. As volume names  201 , names of volumes for storing data update records are designated. As capacities  202 , storage capacities for the respective volumes are designated. As orders of usage  203 , orders of using the volumes are designated. Storage is first performed to the volume of the first order of usage, and when the volume of the first order of usage has become full, storage is performed to the volume of the second order of usage. When the volume of the last order of usage has become full, the volume of the first order of usage is overwritten for storage. In the example as illustrated in  FIG. 2 , division is performed into three storage areas, volume  1 , volume  2  and volume  3 . The capacity of the respective volumes is 100 MB. When storing data update records, it has been set to use the volume  1 , the volume  2  and the volume  3  in this order. This setting is stored in internal storage areas of the server  103  of the active system and of the server  105  of the standby system. The external storage device  104  of the active system and the external storage device  106  of the standby system are used upon dividing them into identical volumes, and both servers use the same settings. 
     FIG. 3  is a view illustrating an example for settings of communicating section setting tables for setting whether or not copy functions are to be used for the respective volumes. A set value used when copy functions are used is referred to as “sync” and a set value when copy functions are not used is referred to as “suspend”. According to the first embodiment of the present invention, a setting for the volume which order of usage is last is set as “suspend” while settings for all other volumes are set as “sync” at the stage of starting backup. According to the second embodiment of the present invention, all volumes are set to “sync” at the stage of starting backup. The communicating section setting tables are stored in the external storage device  104  of the active system or in the external device  106  of the standby system. Hereinafter, explanations will be made on the basis of a case in which the communicating section setting tables are stored in the external storage device  106  of the standby system. 
     FIG. 4  is a functional diagram of a backup system according to the first embodiment of the present invention. The server  103  of the active system  101  comprises a data updating section  401 . The external storage device  104  of the active system comprises a data communicating section  402  for storing therein data update records  403  and data  404 . The server  105  of the standby system comprises a data updating duplicating section  405  and a communication settings judging section  406 . The external storage device  106  of the standby system comprises a data communicating section  407  and a communication setting changing section  408  and stores therein data update records  409 , backup data  410 , and communicating section setting tables  411 . The communicating section setting tables  411  are tables for storing settings of operations of the data communicating section  402  and the data communicating section  407 . As illustrated in  FIG. 3 , it is written in the communicating section setting tables  411  whether copy functions are used for the respective volumes or not. 
     FIG. 5  is a flowchart illustrating an order of operations of the respective sections according to the first embodiment. In the first embodiment, the flow of  FIG. 5  is repeatedly executed, and a newest backup is created in the standby system. In a data sending step  501 , the data updating section  401  and the data communicating section  402  are operated. In the steps of a data updating step  502 , a data receiving step  503 , a data updating duplicating step  504 , a communication settings judging step  505  and a communication settings changing step  506 , the data updating section  401 , the data communicating section  407 , the data updating duplicating section  405 , the communication settings judging section  406 , and the communication settings changing section  408  are operated. Detailed operations of the respective sections will now be recited. 
     FIG. 6  is a flowchart illustrating operations of the data updating section  401 . In process  601 , volumes for storing data update records are determined. The data update records are stored according to the order of usage for the volumes as illustrated in  FIG. 2 . The volume of the first order of usage is first used, and when the volume is full, the next volume is used. In process  602 , the name of a volume  301  as determined in process  601  and the data update records that are to be added in process  605  are noticed to the data communicating section  402 . In process  603 , the notices from the data communicating section  402  are received. In judgment  604 , it is judged whether the content as received in process  603  is “error” or not, and when an “error” has been received, the flow proceeds to termination. In process  605 , data update records that are to be updated in process  606  are added to the data update records  403 . In process  606 , the data  404  are updated. 
   The data communicating section  402  starts operation upon notice of the process  602  of the data updating section  401 . The data communicating section  402  refers to the communicating section setting tables  411  for judging whether the setting of the data communicating section  401  for the volume as noticed by the data updating section  401  is “sync” or not. When it is not “sync”, and “error” is noticed to the data updating section  401 . When it is “sync”, “okay” is noticed to the data updating section, and the data update records as noticed by the data updating section  401  are noticed to the data communicating section  407 . Operations of the data communicating section  402  and the process  601 , the process  602 , the process  603 , and the judgment  604  correspond to the data sending step  501  while the process  605  and the process  606  correspond to the data updating step  502 . 
     FIG. 7  is a flowchart illustrating operations of the data communicating section  407 . The data communicating section  407  starts operations upon notice of the data communicating section  402 . In process  701 , the data update records as noticed by the data communicating section  402  are received. In process  702 , the data update records as received in process  701  are added to the data update records  409 . In process  703 , the data updating duplicating section  405  is noticed that data update records have been added. The operation flow of the data communicating section  407  corresponds to the data receiving step  503 . 
     FIG. 8  is a flowchart illustrating operations of the data updating duplicating section  405 . The data updating duplicating section  405  starts operation upon notice of the process  703  of the data communicating section  407 . Process  801  refers to data update records that have been newly added by the data communicating section  407 . In process  802 , newest backup data  410  are created in accordance with contents of the data update records as referred to. In judgment  803 , it is judged whether the process  801  has referred to the volume up to its end. If reference up to the end of the volume has been made, the flow proceeds to process  804  while when no reference up to the end of the volume has been made, the flow proceeds to termination. Whether the process  801  has referred to up to the end of the volume or not can be judged from the fact whether the place of storage of the data update records as referred to in process  801  is the end of the volume or not. In process  804 , the communication settings judging section  406  is noticed that reference has been made up to the end of the volume. The operation flow of the data updating duplicating section  405  corresponds to the data updating and reproducing step  504 . 
     FIG. 9  is a flowchart illustrating operations of the communication settings judging section  406 . The communication settings judging section  406  starts operation upon notice of the process  804  of the data updating duplicating section  405 . In process  901 , changes in settings are judged. It is judged to change the communicating setting of the volume that has been referred up to the end in the process  801  to “suspend” and to change the communicating setting of the volume that precedes the volume that has been referred up to the end in process  801  by one to “sync”. In process  902 , the changes as judged in the process  901  are noticed to the communication settings changing section  408 . The operation flow of the communication settings judging section  406  corresponds to the communication settings judging step  505 . 
   The communication settings changing section  408  starts operation upon notice of the process  902  of the communication settings judging section  406 . The communication settings changing section  408  changes the communication settings tables  411  in accordance with changes as judged by the communication settings judging section  406 . Operations of the communication settings changing section  408  correspond to the communication settings changing step  506 . 
   The above is the first embodiment. When a large amount of data update records is added in the data updating section  401 , all volumes become full, and data update records are overwritten from the first volume. It is, conventionally, possible that no newest backup data could be created due to overwriting of data update records before the data updating duplicating section  405  refer to. According to the first embodiment, the setting of the data communication section for the volume preceding the volume referred to by the data updating duplicating section  405  is defined as “suspend” so that the data updating section  401  cannot write to the volume preceding the volume referred to by the data updating duplicating section  405 , and addition of data update records is terminated. It is therefore possible to prevent a case in which no newest backup data can be prevented owing to overwriting of update records. 
     FIG. 10  is a functional diagram of the data backup system according to the second embodiment of the present invention. The second embodiment differs from the first embodiment in that a communication settings judging section  1001  has been added to the server  103  of the active system and a communication settings changing section  1002  to the external storage device. Points of differences between the first embodiment and the second embodiment will now be explained. 
     FIG. 11  is a flowchart illustrating an order of operations of the respective sections according to the second embodiment. In the second embodiment, the flow of  FIG. 11  is repeatedly executed for creating newest backups in the standby system. Operations of a data sending step  1101 , a data receiving step  1105 , and a communication settings changing step  1108  are identical to the data sending step  501 , the data receiving step  503 , and the communication settings changing step  506  of the first embodiment, respectively. 
     FIG. 12  is a flowchart illustrating operations of the data updating section  401 . Process  601 , process  602 , process  603 , process  604 , process  605  and process  606  of the flowchart of  FIG. 12  are identical to those of the first embodiment. Judgment  1201  judges whether the volume has become full by adding data update records in process  605 , and when it has become full, the flow proceeds to process  1202 . The process  1202  notices the communication settings judging section  1001  of the name of the volume that has become full. 
     FIG. 13  is a flowchart illustrating operations of the communication settings judging section  1001  of the active system. The communication settings judging section  1001  starts operation upon notice of the process  1202  of the data updating section  401 . In process  1301 , it is judged that the setting of the data communicating section for the volume that has become full is changed to “suspend”. Process  1302  notices the change in the communication setting as judged in the process  1301  to the communication settings changing section  1002 . The operation flow of the communication settings judging section  1001  corresponds to the communication setting judging step  1103 . 
   The communication settings judging section  1002  starts operation upon notice of the process  1302  of the communication settings judging section  1001 . The communication settings changing section  1002  changes the communication section setting tables  411  in accordance with changes in settings of the data communicating section as judged by the communication settings judging section  1001 . Operations of the communication settings changing section  1002  correspond to the communication settings changing step  1104 . 
   The communication settings judging section  406  of the second embodiment judges to change the communication setting to “sync” for the volume that has been referred by the data updating duplicating section  405  up to the end. This judgment is noticed to the communication settings changing section  408 . Operations of the communication settings judging section  406  correspond to the communication settings judging step  1107 . 
   The above is the second embodiment. The communication settings judging section  1001  of the active system sets the setting of the data communicating section for the volume, which has become full upon adding data update records by the data updating section  401 , to “suspend”. The communication settings judging section  406  of the standby system sets the setting of the communicating section for the volume of which reference by the data updating duplicating section  405  has been completed to “sync”. Accordingly, data update records  409  of which reference by the data updating duplicating section  405  has not been completed yet will not be overwritten, and it is possible to prevent a case in which newest backup data cannot be created owing to overwriting of update records.