JP2007249652A - Data mirror type cluster system and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data mirror type cluster system capable of reducing a load applied onto the computer device of an active system during storage device resynchronization to the load in a normal operation. <P>SOLUTION: Normally, data inside the mirroring areas 112 and 212 of the computer devices 1 and 2 of the active system and a standby system are mirrored. When new data are written to the mirroring area 112 while the computer device 2 is stopped, the data and the write record are preserved in the mirroring area 112 and the difference data storage area 312 of a computer device 3 for storing the difference data. When the computer device 2 is restored, the data stored in the difference data storage area 312 are reflected on the mirroring area 222. Before restarting mirroring, the data newly written to the mirroring area 112 and the record are written to the difference data storage area 322. After reflecting all the data written to the difference data storage area 322 on the mirroring area 222, mirroring between the mirroring areas 112 and 212 is restarted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a data mirror type cluster system and its operation method.

  In a cluster system, a computer that has a business application running is the active system, and the computer that takes over the work when the active computer is stopped or the application running on the active system is stopped is the standby system. Call it.

  In the data mirror type cluster system, when data is written to the storage device of the active computer device, the same contents are immediately written to the storage device of the standby computer device.

  In this way, mirroring is always performed so that the data in the storage devices of the active and standby computer devices are the same.

  However, when the standby computer is stopped, new data is written only to the active storage device, so that there is a difference between the data stored in the standby storage device and the active storage device. End up.

  In a conventional data mirror type cluster system, new writes made while the standby computer device is stopped are recorded in the active storage device, and after the standby computer device is restored Is reflected in the standby storage device to match the data in the storage devices of both computer devices (this is called resynchronization).

  Further, when the resynchronization processing ends and the data in both storage devices match, the mirroring of the active and standby storage devices is resumed.

A data mirror type cluster system is described in Patent Document 1, for example.
JP 2005-293315 A

  However, in the conventional data mirror type cluster system, the process of writing to the active storage device, the process of recording the process, and the active computer device while the standby computer device is stopped Since the process of reflecting the record of writing to the storage device stored in the storage device in the standby system proceeds in parallel in the active computer device, the load on the active computer device is large.

  For this reason, there arises a problem that the processing speed of the process that causes access to the application and the storage device activated in the active system is slower than that during normal operation during data resynchronization in the storage device.

  The present invention has been made to solve the above-described problems, and is a data that can reduce the load applied to the active computer device during resynchronization of the storage device to the load during normal operation. It is an object of the present invention to provide a mirror type cluster system and its operation method.

  In order to solve the above problems, a data mirror type cluster system according to the present invention includes an active computer device and a standby computer that takes over the work of the active computer device when a failure occurs in the active computer device. A data mirror type clutter system in which mirroring for reflecting data changes in the storage device included in the active computer device to the storage device included in the standby computer device is normally performed, A differential data storage computer device that stores and holds the changed data when a data change occurs in a storage device included in the active computer device during a period in which a failure occurs in the standby computer device The standby computer device is recovered from a failure The data held in the differential data storage for a computer system is characterized in that so as to reflect the storage device of the standby computer system.

  In the data mirror type cluster system according to the present invention, when the active computer device detects a failure in the standby computer device, the active computer device stops mirroring and a failure occurs in the standby computer device. When a data change occurs in the storage device included in the active computer device during the period, the active computer device transmits the changed data to the differential data storage computer device, When the difference data storage computer apparatus receives the changed data from the active computer apparatus, the difference data storage computer apparatus preferably stores the data in a storage device of the difference data storage computer apparatus.

  In the data mirror type cluster system of the present invention, when the active computer device detects that the standby computer device has recovered from a failure, it notifies the differential data storage computer device to that effect, and Upon receiving the notification that the standby computer device has recovered from the failure, the differential data storage computer device receives the notification from the active computer device and stores it in the storage device of the differential data storage computer device. The standby computer apparatus transmits the data to the standby computer apparatus. When the standby computer apparatus receives the data from the differential data storage computer apparatus, the standby computer apparatus stores the data in the storage apparatus of the standby computer apparatus. It is preferable to preserve.

  In the data mirror type cluster system according to the present invention, the difference data storage computer device has a storage content of the standby storage device that is the same as that of the active storage device after recovery from a failure of the standby computer device. When it is detected that the stored contents are the same, it is preferable to notify the active computer device to that effect, and the active computer device that has received the notification preferably restarts mirroring.

  In the data mirror type cluster system according to the present invention, the difference data storage computer device has a storage content of the standby storage device that is the same as that of the active storage device after recovery from a failure of the standby computer device. When it is detected that the stored contents are the same, the storage device of the differential data storage computer device is changed in the storage device provided in the active computer device during a period when a failure has occurred in the standby computer device. In addition, it is preferable to delete the data stored and held.

  In the data mirror type cluster system of the present invention, in a normal state, when data is changed in the storage device of the active computer device, the active computer device also stores the write record related to the data. While storing in the device, the data and the write record are transmitted to the standby computer device and stored in the storage device of the standby computer device, so that mirroring is performed and the standby computer is stored. If a data change occurs in a storage device included in the active computer device during a period in which a failure has occurred in the device, the active computer device records the changed data and its write record. The difference data storage computer device is transmitted to the difference data storage computer device. When the standby computer apparatus recovers from a failure, the differential data storage computer apparatus stores the data stored in the storage apparatus of the differential data storage computer apparatus and the write record thereof. To the standby computer device, and the standby computer device stores the write record in the storage device of the standby computer device, and based on the write record, It is preferable to store the corresponding data in a predetermined storage area.

  The operation method of the data mirror type cluster system of the present invention comprises: an active computer device; and a standby computer device that takes over the work of the active computer device when a failure occurs in the active computer device. A method of operating a data mirror type clutter system in which mirroring that reflects a change in data generated in a storage device included in the active computer device to a storage device included in the standby computer device is normally performed, If a data change occurs in a storage device included in the active computer device during a period when a failure occurs in the standby computer device, the changed data is transferred to the active system and the standby system. First stored in a computer device for differential data storage different from the first computer device And when the standby computer apparatus recovers from a failure, the data held in the storage device of the differential data storage computer apparatus in the first process is stored in the storage apparatus of the standby computer apparatus. And a second process to be reflected.

  According to the present invention, when the standby computer apparatus recovers the data newly written in the storage device of the active computer apparatus during the period in which the failure has occurred in the standby computer apparatus, Since the processing (resynchronization processing) to be reflected in the storage device of the system computer device is performed in cooperation with the differential data storage computer device and the standby computer device, the current computer device is used during the resynchronization processing. Such a load can be reduced to a load during normal operation. In addition, the resynchronization process can be speeded up by reducing the load on the active computer device during the resynchronization process.

  Embodiments according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing a data mirror type cluster system 100 according to the embodiment.

  As shown in FIG. 1, a data mirror type cluster system 100 according to the present embodiment includes two computer devices 1 and 2, one of which is an active system and the other is a standby system, and one differential data storage computer device. 3.

  The active computer device is a computer device in which a business application is activated.

  In addition, the standby computer device performs operations when a failure occurs in the active computer device (when the active computer device stops or when an application running on the active computer device stops). It is a computer device that takes over.

  The three computer devices 1, 2, 3 are each connected to the network 9, and can communicate with each other via the network 9.

  The computer device 1 includes a storage device 11. In the storage device 11, there are an OS area 111 and a mirroring area 112, and cluster construction software 113 and business software 114 are installed.

  Similarly, the computer apparatus 2 includes a storage device 21. In the storage device 21, there are an OS area 211 and a mirroring area 212, and cluster construction software 213 and business software 214 are installed.

  The differential data storage computer device 3 includes a storage device 31. The storage device 31 includes an OS area 311 and a differential data storage area 312, and differential data management software 313 is installed.

  The business software 114 and 214 are programs for the computer devices 1 and 2 to execute normal business respectively.

  The cluster construction software 113 and 213 is a program for the computer devices 1 and 2 to execute processing for making the storage contents of the mirroring areas 112 and 212 the same.

  OS programs 111, 211, and 311 store OS programs, respectively.

  Normally, the mirroring areas 112 and 212 are stored in the same memory when the computer devices 1 and 2 perform processing according to the program of the cluster construction software 113 and 213, that is, when a normal mirroring operation is executed. The content.

  Further, the differential data management software 313 changes the data to the mirroring area (mirroring area 112 or 212) of the active computer apparatus during a period when a failure has occurred in the standby computer apparatus among the computer apparatuses 1 and 2. If the standby computer apparatus recovers the information stored in the differential data storage area 312 or the information stored in the differential data storage area 312 is stored in the differential data storage area 312 This is a program for the computer device 3 to execute processing to be reflected in the mirroring area.

  During normal operation, the active computer device 1 and the standby computer device 2 transmit, for example, a normal operation signal indicating normal operation to each other at a first predetermined time T1. During the period in which the normal operation signal is received from the other computer device every second predetermined time T2 (T1 <T2), it is recognized that the other computer device is operating normally by processing according to the cluster construction software 113. To do. If a normal operation signal cannot be received from the other computer device every second predetermined time T2, it is recognized that a failure has occurred in the other computer device by processing according to the cluster construction software 113, 213. . Further, after the computer apparatus 1 or 2 recognizes that a failure has occurred in the other computer apparatus and receives a normal operation signal from the other computer apparatus again, the other computer apparatus has recovered from the failure. This is recognized by processing according to the cluster construction software 113, 213.

  Next, normal mirroring operation (operation when the computer devices 1 and 2 are in normal operation) when the computer device 1 is the active system and the computer device 2 is the standby system will be described.

  FIG. 2 is a diagram showing the storage contents of the mirroring area 112 of the active computer apparatus 1 and the mirroring area 212 of the standby computer apparatus 2.

  The mirroring areas 112 and 212 respectively have a data storage area 4 in which data is stored, and a write record storage area 5 in which a write record that is information related to data storage in the data storage area 4 is stored. .

  For example, when the data A in the data storage area 4 is stored, the write record includes information indicating a storage area of the data A in the data storage area 4 and information indicating a time when the data A is stored. It is information including.

  When the computer devices 1 and 2 are normal, mirroring is performed in the mirroring region 112 of the active computer device 1 and the mirroring region 212 of the standby computer device 2.

  That is, as shown in FIG. 2, when data A is written in the data storage area 4 of the active mirroring area 112, the data A is immediately written in the data storage area 4 of the standby mirroring area 212. Further, the write record “a” of data A is stored in the mirroring areas 112 and 212.

  More specifically, when data A is written in the data storage area 4 of the mirroring area 112 by processing according to the business software 114 in the active computer apparatus 1, the active computer apparatus 1 The write record a is written in the write record storage area 5 of the mirroring area 112 by processing according to the construction software 113.

  Subsequently, the active computer device 1 transmits the data A and the write record a to the standby computer device 2.

  When the standby computer apparatus 2 receives the data A and the write record a from the computer apparatus 1, the standby computer apparatus 2 stores the data A in the data storage area 4 of the mirroring area 212, while writing the write record a in the write record storage area of the mirroring area 212. 5 is performed by processing according to the cluster construction software 213.

  Further, the standby computer apparatus 2 transmits storage completion information indicating that the data A and the write record a have been correctly stored to the active computer apparatus 1 by processing according to the cluster construction software 213, and this storage is performed. The computer apparatus 1 that has received the completion information may recognize that the mirroring related to the data A and the write record a has been normally performed. In this case, if the storage completion information cannot be received from the standby computer apparatus 2 within a predetermined time after transmitting the data A and the write record a, the computer apparatus 1 indicates that the computer apparatus 2 has failed. Recognition is performed by processing according to the construction software 113.

  As described above, during normal operation, mirroring is performed in which the storage contents of the mirroring areas 112 and 212 are the same by the cooperation of the active and standby computer apparatuses 1 and 2.

  Next, the operation when the computer apparatus 1 is the active system and the computer apparatus 2 is the standby system and the standby computer apparatus 2 is stopped will be described.

  FIG. 3 is a flowchart showing an operation flow of the data mirror type cluster system 100 of FIG.

  First, the active computer device 1 detects a failure (stop) of the standby computer device 2 by processing according to the cluster construction software 113, and mirrors between the active and standby mirroring regions 112 and 212. Is stopped (step A1).

  That is, in step A1, the active computer device 1 has received a normal operation signal from the standby computer device 2, for example, or cannot receive the storage completion information from the standby computer device 2 during mirroring. ) Is detected, and the occurrence of a failure in the standby computer apparatus 2 is detected. After the detection, even if new data is written in the mirroring area 112, the data and its write record are waited. Do not transmit to the computer device 2 of the system.

  Next, the active computer apparatus 1 determines whether or not a new write has been made in the active mirroring area 112 by processing according to the cluster construction software 113 (step A2). That is, it is determined whether or not a data change has occurred in the storage device 11 included in the active computer device 1 during a period in which a failure has occurred in the standby computer device 2.

  If there is a new write in the active mirroring area 112 during a period in which the standby computer apparatus 2 has failed and mirroring is stopped (Yes in step A2), the difference between the written data and its write record The data is also stored in the difference data storage area 312 of the data storage computer device 3 (step A3).

  In other words, in step A3, the active computer apparatus 1 uses the data for newly writing to the active mirroring area 112 and the recorded data to store the difference data by processing according to the cluster construction software 113. It transmits to the computer apparatus 3. Then, the differential data storage computer apparatus 3 processes the data received from the computer apparatus 1 (data newly written in the active mirroring area 112 and its write record) in accordance with the differential data management software 313. Thus, the difference data storage area 312 is stored.

  Here, the processing of steps A1 to A3 will be described with reference to FIG.

  FIG. 4 is a diagram showing the storage contents of the mirroring area 112 of the active computer apparatus 1, the mirroring area 212 of the standby computer apparatus 2, and the differential data storage area 312 of the differential data storage computer apparatus 3.

  When a failure occurs in the standby computer device 2, the mirroring between the active and standby mirroring regions 112 and 212 stops (step A1). When data B is written to the data storage area 4 in the mirroring area 112 during the period when the mirroring is thus stopped (step A2), the computer apparatus 1 writes the data to the write record storage area 5 in the mirroring area 112. Save b. Subsequently, the computer apparatus 1 transmits the data B and the write record b to the differential data storage computer apparatus 3, and the differential data storage computer apparatus 3 that has received the data B and the write record b receives the difference data storage area 312. The data B and its write record b are stored in (Step A3).

  Further, in step A2 in FIG. 3, when there is no new writing in the active mirroring area 112 (No in step A2), or after the completion of step A3, the active computer apparatus 1 is the standby computer apparatus 2. It is determined by processing according to the cluster construction software 113 whether or not the computer has been restored, that is, whether or not the normal operation signal is received again from the computer apparatus 2 (step A4).

  If the standby computer apparatus 2 has not been restored (No in step A4), the process returns to step A2.

  If the standby computer device 2 has been restored (Yes in step A4), the active computer device 1 indicates that the standby computer device 2 has been restored by processing according to the cluster construction software 113. The difference data storage computer device 3 is notified (step B1).

  Until this notification is received, the answer to step B2 is no, and the differential data storage computer apparatus 3 is on standby by processing according to the differential data management software 313.

  When a notice that the standby computer apparatus 2 is restored is received from the active computer apparatus 1 (Yes in step B2), the process proceeds to step B3.

  In step B <b> 3, the differential data storage computer device 3 determines whether data is stored in the differential data storage area 312 by processing according to the differential data management software 313.

  If there is data in the differential data storage area 312 (Yes in step B3), the differential data storage computer device 3 and the standby computer device 2 cooperate to reflect the data in the standby mirroring region 212, The data and the write record stored in the difference data storage area 312 are erased (step B4).

  That is, in step B4, first, the differential data storage computer device 3 stores the data stored in the differential data storage area 312 (data newly written in the active mirroring area 112 and its write record). The data is transmitted to the standby computer apparatus 2 by processing according to the differential data management software 313. Subsequently, when the standby computer apparatus 2 receives this data, the standby computer apparatus 2 stores (reflects) the data in the mirroring area 212 by a process according to the cluster construction software 213, and also writes a write completion signal indicating that effect. Is transmitted to the differential data storage computer device 3. Subsequently, when the differential data storage computer device 3 receives a write completion signal from the standby computer device 2, the data stored in the differential data storage region 312 is processed by processing according to the differential data management software 313. to erase.

  Here, the processing of steps A4 to B4 will be described with reference to FIGS.

  FIG. 5 shows the storage contents of the mirroring area 112 of the active computer apparatus 1, the mirroring area 212 of the standby computer apparatus 2, and the differential data storage area 312 of the differential data storage computer apparatus 3.

  When the standby computer apparatus 2 is restored (Yes in step A4), the process proceeds to step B3 through steps B1 and B2.

  In step B3, the computer apparatus 3 determines the presence or absence of data in the difference data storage area 312, but if the data B (and its write record b) exists as shown in FIG. 4 (Yes in step B3), the computer The device 3 transmits the data B and the write record b to the computer device 2.

  The computer apparatus 2 stores the received write record b in the mirroring area 212 as shown in FIG. 5, and based on the write record b, the data B is stored in a predetermined storage area in the mirroring area 212 as shown in FIG. Save (reflect). Furthermore, the computer apparatus 2 transmits a write completion signal indicating that the reflection has been completed to the differential data storage computer apparatus 3. When receiving the write completion signal from the computer apparatus 2, the differential data storage computer apparatus 3 erases the data B and the write record b from the differential data storage area 312. As a result, the state shown in FIG. 5 is obtained.

  Subsequent to step B4, as in step A2, it is determined whether new writing has occurred in the active mirroring area 112 (step B5).

  When there is new writing (Yes in Step B5), the process proceeds to Step B6.

  In step B6, as in step A3, the data written to the mirroring area 112 and its write record are also stored in the difference data storage area 312.

  Here, the processing of steps B5 to B6 will be described with reference to FIG.

  FIG. 6 is a diagram showing the storage contents of the mirroring area 112 of the active computer apparatus 1, the mirroring area 212 of the standby computer apparatus 2, and the differential data storage area 312 of the differential data storage computer apparatus 3.

  As shown in FIG. 6, when data C is written to the active mirroring area 112 after the state of FIG. 5 (Yes in step B5), the data C and its data are processed in the same manner as the processing described in FIG. The write record c is written in the difference data storage area 312 (step B6).

  When there is no new writing (No in Step B5), or after Step B6 is completed, the process returns to Step B3.

  Here, processing when the process proceeds from step B6 to step B3 will be described with reference to FIG.

  FIG. 7 is a diagram showing the storage contents of the mirroring area 112 of the active computer apparatus 1, the mirroring area 212 of the standby computer apparatus 2, and the differential data storage area 312 of the differential data storage computer apparatus 3.

  If the process proceeds from step B6 to step B3, the answer is yes in step B3, and the process proceeds to step B4.

  In this case, the write record c stored in the differential data storage area 312 is stored in the standby mirroring area 212 and the data C is mirrored based on the write record c, as in the operations of FIGS. Write to area 212. Thereafter, the data C in the difference data storage area 312 and the written record c thereof are erased (FIG. 7).

  If it is determined in step B3 that there is no data in the differential data storage area 312 (No in step B3), the process proceeds to step B7, and the mirroring between the active and standby mirroring areas 112 and 212 is resumed.

  Note that the determination in step B3 that there is no data in the difference data storage area 312 is that mirroring of the storage device 21 of the standby computer device 2 after recovery from the failure of the standby computer device 2 This means that the difference data storage computer apparatus 3 has detected that the storage contents of the area 212 are the same as the storage contents of the mirroring area 112 of the storage apparatus 11 of the active computer apparatus 1.

  In step B 7, first, the difference data storage computer device 3 sends the no-data information indicating that there is no data in the difference data storage region 312 to the active computer device 1 by processing according to the difference data management software 313. Send. This no-data information is stored in the mirroring area 212 of the storage device 21 of the standby computer device 2 after the recovery from the failure of the standby computer device 2 in the storage device 11 of the active computer device 1. It can be considered as information indicating that the stored contents in the mirroring area 112 are the same. Upon receiving the no-data information, the active computer device 1 transmits resumption information indicating that mirroring is to be resumed to the standby computer device 2 by processing according to the cluster construction software 113. When the standby computer apparatus 2 receives the resume information, the standby computer apparatus 2 resumes mirroring by processing according to the cluster construction software 213.

  Here, the operation after the mirroring is resumed from step B3 to step B7 will be described with reference to FIG.

  FIG. 8 is a diagram showing the storage contents of the mirroring area 112 of the active computer apparatus 1, the mirroring area 212 of the standby computer apparatus 2, and the differential data storage area 312 of the differential data storage computer apparatus 3.

  After the processing of FIG. 7, there is no writing to the active mirroring area 112, all the data in the differential data storage area 312 is erased (No in step B3), and between the active and standby mirroring areas 112 and 212. When the data D is written to the active mirroring area 112 as shown in FIG. 8 after the mirroring is resumed (step B7), as in the operation of FIG. In addition, data D is written as shown in FIG. Further, the write record d of the data D is also stored in the mirroring areas 112 and 212 as in the operation of FIG. 2 (FIG. 8).

  According to the embodiment as described above, data newly written in the mirroring area 112 of the active computer device 1 during a period in which a failure has occurred in the standby computer device 2 is stored in the standby computer device. Since the processing (resynchronization processing) to be reflected in the mirroring area of the computer device 2 when the computer 2 is restored is performed in cooperation with the differential data storage computer device 3 and the standby computer device 2, In addition, the load applied to the active computer device 1 can be reduced to the load during normal operation. In addition, the resynchronization process can be speeded up by reducing the load on the active computer device 1 during the resynchronization process.

  Accordingly, the processing speed of the business application (application according to the business software 113) running on the active computer device 1 and the response to the client process are the same as those during normal operation even during resynchronization processing. It can be applied to the realization of a cluster system that needs to be kept equal.

  In the above embodiment, the computer apparatus 1 is the active system and the computer apparatus 2 is the standby system. However, the same applies to the computer apparatus 1 being the standby system and the computer apparatus 2 being the active system.

  Further, in the above embodiment, for the sake of simplicity, an example in which only two computer devices 1 and 2 are used to perform mirroring at normal times has been described. However, mirroring is performed by three or more computer devices. Also good.

1 is a block diagram showing a data mirror type cluster system according to an embodiment. It is a figure which shows the memory content of the mirroring area | region of the computer system of an active system and a standby system. It is a flowchart which shows the flow of operation | movement of a data mirror type | mold cluster system. It is a figure which shows the memory content of the mirroring area | region of the computer system of an active system, and a standby system, and the difference data storage area of the computer apparatus for difference data storage. It is a figure which shows the memory content of the mirroring area | region of the computer system of an active system, and a standby system, and the difference data storage area of the computer apparatus for difference data storage. It is a figure which shows the memory content of the mirroring area | region of the computer system of an active system, and a standby system, and the difference data storage area of the computer apparatus for difference data storage. It is a figure which shows the memory content of the mirroring area | region of the computer system of an active system, and a standby system, and the difference data storage area of the computer apparatus for difference data storage. It is a figure which shows the memory content of the mirroring area | region of the computer system of an active system, and a standby system, and the difference data storage area of the computer apparatus for difference data storage.

Explanation of symbols

1, 2 Computer devices 11, 21, 31 Storage devices 111, 211, 311 OS areas 112, 212 Mirroring areas 113, 213 Cluster construction software 114, 214 Business software 3 Differential data storage computer 312 Differential data storage area 313 Difference data management software a, b, c, d Write record to mirroring area A, B, C, D Data written to mirroring area

Claims (7)

An active computer device and a standby computer device that takes over the work of the active computer device when a failure occurs in the active computer device, and a storage device included in the active computer device In the data mirror type clutter system in which the mirroring that reflects the change of the generated data in the storage device provided in the standby computer apparatus is normally performed,
A differential data storage computer that stores and holds the changed data when a data change occurs in a storage device included in the active computer device during a period in which a failure occurs in the standby computer device Further comprising a device,
Data stored in the differential data storage computer device is reflected in the storage device of the standby computer device when the standby computer device recovers from a failure. Mirror type cluster system. When the active computer device detects a failure in the standby computer device, it stops mirroring,
If a data change occurs in a storage device included in the active computer device during a period in which a failure occurs in the standby computer device, the active computer device uses the changed data. To the difference data storage computer device,
The differential data storage computer device receives and stores the changed data from the active computer device, and stores the data in a storage device of the differential data storage computer device. 2. A data mirror type cluster system according to 1. When the active computer device detects that the standby computer device has recovered from a failure, it notifies the differential data storage computer device to that effect,
Upon receiving a notification that the standby computer device has recovered from a failure, the differential data storage computer device receives the notification from the active computer device and stores it in the storage device of the differential data storage computer device. The data being transmitted to the standby computer device,
3. The data mirror according to claim 2, wherein when the standby computer apparatus receives the data from the differential data storage computer apparatus, the standby computer apparatus stores the data in a storage device of the standby computer apparatus. Type cluster system.   The differential data storage computer device detects that the storage content of the standby storage device is the same as the storage content of the active storage device after recovery from a failure of the standby computer device The data mirror according to any one of claims 1 to 3, wherein the active computer device notifies the active computer device to that effect, and the active computer device that receives the notification restarts mirroring. Type cluster system.   The differential data storage computer device detects that the storage content of the standby storage device is the same as the storage content of the active storage device after recovery from a failure of the standby computer device Erasing data that has been changed in the storage device of the active computer device and stored in the storage device of the differential data storage computer device during a period when a failure has occurred in the standby computer device The data mirror type cluster system according to any one of claims 1 to 4, wherein the data mirror type cluster system is provided. Under normal circumstances, when a change in data occurs in the storage device of the active computer device, the active computer device also stores a write record relating to the data in the storage device, while the data and the data By sending a write record to the standby computer device and storing it in the storage device of the standby computer device, mirroring is performed,
If a data change occurs in a storage device included in the active computer device during a period in which a failure occurs in the standby computer device, the active computer device uses the changed data. And the written record thereof is transmitted to the differential data storage computer device and stored in the storage device of the differential data storage computer device,
When the standby computer device recovers from a failure, the differential data storage computer device stores the data stored in the storage device of the differential data storage computer device and its write record. The standby computer device stores the write record in the storage device of the standby computer device, and based on the write record, stores the data corresponding to the write record in a predetermined manner. 2. The data mirror type cluster system according to claim 1, wherein the data mirror type cluster system is stored in a storage area. An active computer device and a standby computer device that takes over the work of the active computer device when a failure occurs in the active computer device, and a storage device included in the active computer device In a method of operating a data mirror type clutter system in which mirroring that reflects a change in data that has occurred in a storage device included in the standby computer device is normally performed,
If a data change occurs in a storage device included in the active computer device during a period in which a failure occurs in the standby computer device, the changed data is transferred to the active system and the standby computer. A first step of storing and holding the difference data storage computer device different from the computer device of the system;
When the standby computer device recovers from a failure, the data held in the storage device of the differential data storage computer device in the first process is reflected in the storage device of the standby computer device. 2 process,
A method of operating a data mirror type clutter system, comprising:

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