JP2005050104A - Data backup method and virtual magnetic tape device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent reduction of reuse efficiency of a magnetic tape due to difference of a backup cycle. <P>SOLUTION: For storing a virtual medium of a magnetic disk drive 3 in a magnetic tape via a magnetic tape drive 5, a magnetic tape matching the backup cycle of the virtual medium is selected and data of the virtual medium are stored in the selected magnetic tape. Only the virtual media having mutually similar backup periods are stored in each magnetic tape, and necessity of a waiting time for reuse, which is retarded conventionally until the virtual medium having a relatively long backup cycle becomes unnecessary, of the magnetic tape can be removed. Consequently, overwriting to the magnetic tape can be carried out smoothly, and the reuse efficiency of the magnetic tape is improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention improves a data backup method and a virtual magnetic tape device that use a primary storage magnetic disk drive and a secondary storage magnetic tape drive to store data of a host device on a magnetic tape as a secondary backup. About.

  Magnetic disk drive for primary storage that stores the data of the host device as a virtual medium, and magnetic tape for secondary storage that selectively uses a plurality of magnetic tapes to store the virtual medium of the magnetic disk drive on the magnetic tape Data backup that uses a drive to store the virtual medium of the magnetic disk drive on the magnetic tape via the magnetic tape drive, and frees up the storage area of the magnetic disk drive in which the virtual medium was stored. Methods and virtual magnetic tape devices are known.

  However, the primary storage virtual medium storing the data to be overwritten in a short backup cycle and the primary storage virtual medium storing the data to be overwritten in a long backup cycle are the same on the magnetic tape for secondary storage. Once stored, the magnetic tape cannot be overwritten until a virtual medium that is overwritten with a long backup cycle becomes unnecessary, and there is a problem in that the efficiency of reusing the magnetic tape is reduced.

  Further, a primary storage virtual medium storing data to be overwritten with a short backup cycle and a primary storage virtual medium storing data to be overwritten with a long backup cycle are used on the same secondary storage magnetic tape. It is conceivable to re-arrange virtual media across a plurality of magnetic tapes after they have been stored and rearrange virtual media with the same backup cycle to the same magnetic tape. Data exchange with the magnetic disk drive is frequently performed, the load on the apparatus is increased, and reading / writing with respect to the magnetic tape is frequently performed, so that the magnetic tape is likely to be damaged such as wear.

  For example, a data copying / restoring system disclosed in Patent Document 1 and a storage medium management system disclosed in Patent Document 2 have already been proposed as techniques for increasing the reuse efficiency of magnetic tape.

  The data copying / restoring system disclosed in Patent Document 1 erases the previous generation virtual magnetic tape from the second level magnetic tape when migrating the data of the first level virtual magnetic tape to the second level magnetic tape. Thus, the magnetic tape reuse efficiency is improved, that is, in terms of the reuse efficiency, the conventional technique is not for increasing the reuse efficiency of the magnetic tape storing the virtual medium having a predetermined storage period.

  In addition, the storage medium management method disclosed in Patent Document 2 guarantees the continuity of the virtual medium by selecting a magnetic tape having a lifetime that is suitable for the required storage period of the virtual medium, in other words, due to deterioration of the magnetic tape. This is just a way to increase the operational efficiency of the device by eliminating the need for re-backup processing to prevent the virtual media from disappearing. The data on the magnetic tape is released and the magnetic tape can be effectively reused. It is not intended to reduce the required number.

JP-A-11-272426 JP-A-8-7533

  An object of the present invention is to prevent a decrease in magnetic tape reuse efficiency due to a difference in the backup cycle of virtual media, an increase in load on the apparatus due to a rearrangement process of virtual media on the magnetic tape, and wear of the magnetic tape. An object of the present invention is to provide a data backup method and a virtual magnetic tape device that can efficiently reuse a magnetic tape for secondary storage.

In the data backup method of the present invention, a magnetic disk drive for primary storage that stores data of a host device as a virtual medium and a plurality of magnetic tapes are selectively used to store the virtual medium of the magnetic disk drive on the magnetic tape. The secondary storage magnetic tape drive is used to store the virtual medium of the magnetic disk drive on the magnetic tape via the magnetic tape drive, and the storage area of the magnetic disk drive in which the virtual medium is stored is released. In the data backup method to be reused,
The host device sets a storage virtual medium cycle for each magnetic tape in correspondence with a backup cycle in which data is overwritten on the virtual medium of the magnetic disk drive,
A configuration in which when a virtual medium of a magnetic disk drive is stored on a magnetic tape via a magnetic tape drive, a magnetic tape corresponding to a backup cycle of the virtual medium is selected and data of the virtual medium is stored Have

  With the above configuration, each virtual tape stores only a virtual medium whose backup cycle approximates, and waits for reuse of the magnetic tape until a virtual medium having a relatively long backup cycle becomes unnecessary. This eliminates the need for overwriting on the magnetic tape, thereby improving the efficiency of reusing the magnetic tape. Therefore, the number of magnetic tapes required for secondary storage is also suppressed. At the same time, there is no need to relocate virtual media between multiple magnetic tapes according to the backup cycle, reducing redundant data exchange between the magnetic tape drive and magnetic disk drive, and reducing the load on the device. Is reduced, and the number of times of reading and writing with respect to the magnetic tape is reduced, so that the substantial durability of the magnetic tape can be improved.

  Further, when the virtual medium of the magnetic disk drive is stored on the magnetic tape via the magnetic tape drive, it is desirable to select a virtual medium having an old storage history and store it on the magnetic tape.

The storage efficiency of the magnetic disk drive can be maintained in an appropriate state by storing the old virtual medium that is considered unnecessary to be frequently accessed from the host device on the magnetic tape and releasing the storage area of the magnetic disk drive. .
In addition, a method may be considered in which a priority order is set for each virtual medium and stored on the magnetic tape in order from the lowest priority order.

  Further, virtual media having the same storage history may be continuously selected until a necessary amount of the storage area of the magnetic disk drive is released.

  Even if you select a virtual medium with an old storage history and store it on the magnetic tape, or select a virtual medium with a low priority and store it on the magnetic tape, Virtual media having backup cycles equivalent to the selected virtual media are selected together, and the storage area of the magnetic disk drive can be greatly recovered.

  In addition, when storing the virtual media of a magnetic disk drive on a magnetic tape via a magnetic tape drive, the magnetic tape in use is preferentially selected, and only when there is no magnetic tape in use, a new magnetic It is desirable to select a tape.

  Since virtual media are continuously stored on the magnetic tape, the number of magnetic tapes required for secondary storage can be suppressed.

The virtual magnetic tape device of the present invention uses a magnetic disk drive for primary storage that stores data of a host device as a virtual medium and a plurality of magnetic tapes selectively to use the virtual medium of the magnetic disk drive as a magnetic tape. The magnetic tape drive for secondary storage to be stored, the magnetic disk drive and the magnetic tape drive are driven and controlled, the virtual medium of the magnetic disk drive is stored on the magnetic tape via the magnetic tape drive, and the virtual medium is stored. A virtual magnetic tape device comprising a control means for releasing the storage area of the magnetic disk drive, and in order to achieve the same problem as described above,
Control means for a backup cycle storage table for storing a backup cycle for each virtual medium in which a host device overwrites data on a virtual medium of a magnetic disk drive and a rotation cycle storage table for storing a storage virtual medium cycle for each magnetic tape Along with
When the virtual medium of the magnetic disk drive is stored on the magnetic tape via the magnetic tape drive, the control means refers to the backup cycle storage table and the rotation cycle storage table and corresponds to the backup cycle of the virtual medium. A magnetic tape selection function for selecting a magnetic tape and storing data of the virtual medium is provided.

  When storing the virtual medium of the magnetic disk drive on the magnetic tape, the control means refers to the backup cycle storage table and the rotation cycle storage table, selects the magnetic tape corresponding to the backup cycle of the virtual medium, Since the data of the virtual medium is stored, only the virtual medium having an approximate backup cycle is stored on each magnetic tape. Therefore, there is no need to wait for the reuse of the magnetic tape until a virtual medium having a relatively long backup cycle is no longer needed, and the reuse efficiency of the magnetic tape is improved, and the magnetic tape required for secondary storage is used. Is also suppressed. At the same time, since there is no need to perform virtual media relocation processing between multiple magnetic tapes according to the backup cycle, the exchange of redundant data between the magnetic tape drive and the magnetic disk drive is reduced. Since the load is reduced and the number of times of reading and writing on the magnetic tape is reduced, the substantial durability of the magnetic tape can be improved.

In addition, a field for storing the execution date of overwriting data on the virtual medium is provided in the backup cycle storage table,
When the virtual medium of the magnetic disk drive is stored on the magnetic tape via the magnetic tape drive, the control means selects the virtual medium having the old overwrite execution date with reference to the backup cycle storage table and selects the magnetic tape It is preferable to provide a virtual medium automatic selection function to be stored in.

  The use efficiency of the magnetic disk drive is also improved by storing the old virtual medium considered unnecessary to be frequently accessed from the host device on the magnetic tape and releasing the storage area of the magnetic disk drive.

  Further, when the virtual medium of the magnetic disk drive is stored on the magnetic tape via the magnetic tape drive, the control means has the same backup cycle until the storage area of the magnetic disk drive is released by a necessary amount. It is possible to provide a virtual medium continuous selection function that continues to select virtual media having

  Since the virtual media are collectively selected and stored on the magnetic tape, the storage area of the magnetic disk drive can be collectively released.

  In addition, when the virtual medium of the magnetic disk drive is stored on the magnetic tape via the magnetic tape drive, the control means preferentially selects the magnetic tape in use and there is no magnetic tape in use. A magnetic tape selection order determining function for selecting a new magnetic tape can be provided.

  Since virtual media are continuously stored on the magnetic tape, the number of magnetic tapes required for secondary storage can be suppressed.

  Further, this control means can be provided with a backup cycle setting function for setting the backup cycle given from the host device in the backup cycle storage table.

  Alternatively, a dedicated management system may be constructed separately from the host device, and a backup cycle may be given to the control means from the management system and set in the backup cycle storage table.

  Furthermore, it is also possible to provide the control means with a backup cycle automatic setting function for obtaining a backup cycle based on the data overwrite execution date and setting it in the backup cycle storage table.

When such a configuration is applied, it is not necessary for the operator to input the backup cycle for each virtual medium by operating the host device or the management system, so that the data backup operation is further simplified. The control means can obtain a basic backup cycle based on the difference between the latest overwrite execution date and the immediately preceding overwrite execution date.
Further, the storage virtual medium period of the rotation period storage table corresponding to the magnetic tape in which no valid data is stored can be set unset. A magnetic tape having a storage virtual medium period not set can store any virtual medium having any backup period, and when the virtual medium is stored, the backup period of the virtual medium is set as the storage virtual medium period. As a result, the rewritable magnetic tape medium can be shared for storing virtual media having different backup cycles.

  In the data backup method and virtual magnetic tape apparatus of the present invention, only the virtual medium whose backup cycle is approximated is stored in each magnetic tape. Therefore, the virtual medium is randomly placed on the magnetic tape regardless of the length of the backup cycle. Unlike conventional data backup methods and apparatuses that store data, there is no need to wait for reuse of the magnetic tape until a virtual medium having a relatively long backup cycle is no longer needed, and the magnetic tape can be overwritten smoothly. As a result, the recycling efficiency of the magnetic tape is improved. As a result, the number of magnetic tapes required for secondary storage is also suppressed. At the same time, there is no need to relocate virtual media between multiple magnetic tapes according to the backup cycle, reducing redundant data exchange between the magnetic tape drive and magnetic disk drive, and reducing the load on the device. Is reduced, and the number of times of reading and writing with respect to the magnetic tape is reduced, so that the substantial durability of the magnetic tape can be improved.

  In addition, when storing a virtual medium of a magnetic disk drive on a magnetic tape via a magnetic tape drive, select a virtual medium having an old storage history that is considered unnecessary to be frequently accessed from a host device and select it on the magnetic tape. Since the data is stored, it is not necessary to frequently recover from the magnetic tape to the magnetic disk drive, and the utilization efficiency of the magnetic disk drive can be maintained in an appropriate state.

  Furthermore, the virtual disk having the same backup period is continuously selected until the necessary amount of storage area of the magnetic disk drive is released, so that the storage area of the magnetic disk drive can be released collectively. it can.

  In addition, when storing a virtual medium of a magnetic disk drive on a magnetic tape via a magnetic tape drive, the magnetic tape in use is preferentially selected, and a new magnetic tape is used only when there is no magnetic tape in use. Thus, the virtual medium can be continuously stored on the magnetic tape, and the number of magnetic tapes required for secondary storage can be suppressed.

  In particular, in the virtual magnetic tape device of the present invention, the control means is provided with a backup cycle setting function for setting the backup cycle given from the host device in the backup cycle storage table. It can be set arbitrarily according to the judgment of the operator.

  In addition, a backup cycle automatic setting function is provided to determine the backup cycle based on the data overwrite execution date and set it in the backup cycle storage table, so that the operator does not need to input the backup cycle for each virtual medium. Data backup can be easily performed.

  Here, the operation principle of the best mode to which the present invention is applied will be briefly described with reference to FIG.

  The virtual magnetic tape device 1 of FIG. 1 includes a magnetic disk drive 3 for primary storage that stores data of the host device 2 as a virtual medium, and a virtual medium of the magnetic disk drive 3 that selectively uses a plurality of magnetic tapes. Has a magnetic tape drive 5 for secondary storage. Further, the virtual magnetic tape device 1 drives and controls the magnetic disk drive 3 and the magnetic tape drive 5, stores the virtual medium of the magnetic disk drive 3 on the magnetic tape via the magnetic tape drive 5, and stores the virtual medium. Control means 6 for releasing the storage area of the magnetic disk drive 3 is provided.

  The control means 6 is provided with a virtual medium rotation management unit 7 composed of a nonvolatile memory, and the virtual medium rotation management unit 7 is provided with a backup cycle storage table and a rotation cycle storage table.

  The backup cycle storage table stores, for each virtual medium, the backup cycle in which the host device 2 overwrites data on the virtual medium of the magnetic disk drive 3, and the rotation cycle storage table stores the rotation cycle for each magnetic tape. The virtual medium period is stored.

  The setting of the backup cycle for the backup cycle storage table is performed by writing the backup cycle input by the operator using the host device 2 into the backup cycle storage table by the internal processing of the control means 6, or with the host device 2 This is achieved by performing a similar input operation using another management system 8 (backup cycle setting function). Alternatively, the control means 6 looks at the execution date of overwriting on each virtual medium of the magnetic disk drive 3, and obtains a basic backup cycle based on the difference between the latest overwriting execution date and the immediately preceding overwriting execution date. Write the backup cycle to the backup cycle storage table (automatic backup cycle setting function).

  When the operator explicitly sets the backup cycle for the backup cycle storage table using the host device 2 or the management system 8, the rotation cycle for each magnetic tape is stored in the rotation cycle storage table by the same procedure. The backup cycle of the virtual medium stored on each magnetic tape can be set. Further, the control means 6 monitors the execution date of overwriting for each virtual medium of the magnetic disk drive 3, and obtains a basic backup cycle based on the difference between the latest overwriting execution date and the immediately preceding overwriting execution date. As with writing to the periodic storage table, the latest recording date is stored in the rotational period storage table, and the basic rotation period is set based on the difference between the overwrite date of the magnetic tape and the recording date immediately before it. be able to. As in this case, when the backup cycle is not known in advance, when the virtual medium is stored on a new magnetic tape, the backup cycle of the virtual medium is set as the storage virtual medium cycle of the magnetic tape. By changing this basic rotation cycle by using the host device 2 or the management system 8, the magnetic tape can be rotated before the virtual medium can no longer be stored on the magnetic tape, or different. It is possible to calculate a difference from the rotation period of another magnetic tape that stores the virtual medium of the backup period, and to change the correspondence of the magnetic tape so that the difference is reduced.

  If the storage area of the primary storage magnetic disk drive 3 is insufficient after the above initial setting process is completed, some of the virtual media of the magnetic disk drive 3 are selected and the magnetic The data is stored on the magnetic tape via the tape drive 5, the storage area of the magnetic disk drive 3 storing the virtual medium is released, and data can be overwritten in the storage area.

  The selection criteria of the virtual medium to be stored on the magnetic tape are based on the new or old of the storage history of the virtual medium or the priority of the importance of the data stored in the virtual medium (virtual medium automatic selection function). At this time, virtual media having the same backup cycle may be selected together (virtual media continuous selection function). According to the new or old storage history of the virtual medium, when data is overwritten on the virtual medium of the magnetic disk drive 3, the control means 6 writes the data overwriting execution date in a specific field of the backup cycle storage table. Then, the control unit 6 can recognize the state.

  When the virtual medium of the magnetic disk drive 3 is stored on the magnetic tape via the magnetic tape drive 5, the control means 6 refers to the backup cycle storage table and the rotation cycle storage table of the virtual medium rotation management unit 7, and By selecting the magnetic tape corresponding to the backup period of the medium and storing the data of the virtual medium (magnetic tape selection function), only the virtual medium whose backup period approximates is stored on each magnetic tape. .

  In addition, if there are several magnetic tapes corresponding to the backup cycle of the virtual medium, the magnetic tape in use is preferentially selected, and a new magnetic tape is inserted only when there is no magnetic tape in use. By selecting (magnetic tape selection order determining function), virtual media are continuously stored on the magnetic tape, and the number of magnetic tapes required for secondary storage is suppressed.

As described above, by storing only virtual media whose backup cycle approximates to each magnetic tape, the period until all the data stored on the magnetic tape is overwritten and the magnetic tape can be reused. This eliminates the restriction that the magnetic tape cannot be reused until a virtual medium having a relatively long backup cycle is no longer needed, and allows the magnetic tape to be overwritten smoothly. Improve usage efficiency.
At the same time, it eliminates the inconvenience that a virtual medium rearrangement process is required between a plurality of magnetic tapes according to the backup cycle, and eliminates redundant data exchange between the magnetic tape drive 5 and the magnetic disk drive 3. This reduces the load on the internal processing of the virtual magnetic tape device 1 and also reduces the number of times of reading and writing to the magnetic tape to prevent the magnetic tape from being worn, thereby improving the substantial durability of the magnetic tape. .

  Next, some specific embodiments will be described in detail with reference to the drawings.

  FIG. 1 shows a connection relationship between a virtual magnetic tape device 1 of an embodiment to which a data backup method of the present invention is applied, a host device 2 and a management system 8, and a virtual magnetic tape device 1 constituting the main part of the system. It is the functional block diagram shown about the internal structure of.

  The virtual magnetic tape device 1 is either a magnetic disk drive 3 for primary storage that stores data of the host device 2 as a virtual medium, or a virtual medium of the magnetic disk drive 3 selectively using a plurality of magnetic tapes. A magnetic tape drive 5 for secondary storage to be stored on the magnetic tape. The host device here is, for example, a computer system such as a workstation or a personal computer.

  As the magnetic tape drive 5 for secondary storage, for example, as shown in FIG. 2, a magnetic tape read & writer 9, a tape storage shelf 10 for storing a plurality of magnetic tapes, and a magnetic tape read & writer 9 For example, a magnetic tape library device including an accessor 11 for exchanging magnetic tape between the tape storage rack 10 and the tape storage shelf 10 can be used.

  The configuration of the magnetic tape read & writer 9 and the accessor 11 constituting the main part of the magnetic tape drive 5 for secondary storage and the configuration of the magnetic disk drive 3 for primary storage are already known. The drive is controlled by the control means 6 of the virtual magnetic tape device 1.

  As shown in FIG. 2, the main part of the control unit 6 includes a CPU 12 as a calculation unit, a ROM 13 storing a drive control program for the CPU 12, a RAM 14 used for temporary storage of data, and a virtual medium rotation management. The non-volatile memory functioning as the unit 7 and the interface 15 for transmitting information to and from the host device 2 and the management system 8 include the above-described magnetic disk drive 3, magnetic tape read & writer 9, The accessor 11 is driven and controlled by a command from the CPU 12 via the input / output circuit 16.

FIG. 3 is a conceptual diagram illustrating an example of a backup cycle storage table provided in the virtual medium rotation management unit 7 including a nonvolatile memory, and FIG. 4 is a conceptual diagram illustrating an example of a rotation cycle storage table.
In this embodiment, the setting of the backup cycle for the backup cycle storage table and the setting of the rotation cycle for the rotation cycle storage table are performed by the operator using the host device 2 or the management system 8 and the numeric keypad operation. This is achieved by the CPU 12 constituting the unit setting these numerical values in a table (backup cycle setting function).

Further, as shown in FIG. 3, in the update history storage field given to the backup cycle storage table, the latest backup execution date performed on the virtual medium from the host device 2 is stored by the internal processing of the CPU 12. It is updated and stored as a history.
Further, as shown in FIG. 4, the status storage field assigned to the rotation cycle storage table is stored by the internal processing of the CPU 12 when the first backup processing is performed from the magnetic disk drive 3 to the magnetic tape. The flag indicating that the magnetic tape is in use is set in the field corresponding to the magnetic tape. In the status storage field corresponding to the magnetic tape that does not store the backup data, a flag indicating that it can be used is set. When data is stored over the entire length of the magnetic tape, the used flag is set. . If all the virtual media stored on the magnetic tape become invalid data by being overwritten from the host device 2, the magnetic tape can be reused and the flag indicating that it can be used is reset. It has become so.

  An example of a procedure for backing up a virtual medium from the host device 2 to the magnetic disk drive 3 is shown in FIG.

  In this example, the entire backup relating to the data to be backed up is performed on Sunday, and on each day of the week from Monday to Saturday, a differential backup is performed in which only changes from the data on Sunday are stored. Use a total of 10 virtual media for backup, leave differential backups for each day of the week from Monday to Saturday, and leave all backups updated every week up to the previous 3 weeks Therefore, the six virtual media from the virtual medium (1) to the virtual medium (6) are used for differential backup, and the four virtual media from the virtual medium (7) to the virtual medium (10) are used for overall backup. using.

  Therefore, for example, the change between the Sunday data and the last data on Monday is stored in the virtual medium (1) as a differential backup in a one-week cycle, and the Sunday data and Tuesday are stored in the virtual medium (2). The change from the last data is stored as a differential backup in a cycle of one week. Similarly, each of the virtual medium (3) to the virtual medium (6) includes a change between the Sunday data and the last data on Wednesday, and the data between the Sunday data and the last data on Thursday. Changes, changes between Sunday data and last data on Friday, changes between Sunday data and last data on Saturday are stored as differential backups for each virtual medium in a one-week cycle. .

  In addition, in each of the four virtual media of the virtual medium (7) to the virtual medium (10), the entire backup every Sunday is stored in a cycle of four weeks (one month cycle), and the virtual media (7) to virtual By combining the four virtual media of the medium (10), the entire backup updated every Sunday is stored for a total of four weeks (one month) including the current week.

  Next, the overall operation of the virtual magnetic tape device 1 of this embodiment and the virtual medium automatic selection function with reference to the flowcharts of FIGS. 6 to 8 showing the outline of the processing executed by the CPU 12 of the control means 6 The processing operation of the CPU 12 functioning as the realization means, the virtual medium continuous selection function realization means, the magnetic tape selection function realization means, and the magnetic tape selection order determination function realization means will be specifically described.

  FIG. 6 shows the main part of the control means 6 for storing the virtual medium of the magnetic disk drive 3 on the magnetic tape and then releasing the storage area of the magnetic disk drive 3 in which the virtual medium is stored so that it can be reused. 7 is a flowchart showing an overall flow of secondary backup processing executed by the CPU 12 constituting the unit, and FIG. FIG. 8 is a flowchart showing the medium allocation process of the CPU 12 that realizes the magnetic tape selection function and the magnetic tape selection order determination function.

  The secondary backup process of FIG. 6 is started based on an instruction from the operator when the unused capacity of the magnetic disk drive 3 becomes insufficient, or the storage capacity of the magnetic disk drive 3 It is automatically activated by the internal processing of the CPU 12 that keeps an eye on the unused portion.

  The CPU 12 that has started the secondary backup process of FIG. 6 first executes a virtual medium selection process (step S101) related to selection of a virtual medium in the magnetic disk drive 3 to be subjected to secondary backup.

  Here, as an example, after selecting a virtual medium having an old storage history so that the storage area of the magnetic disk drive 3 is released to a necessary amount, several virtual media having the same backup cycle as the virtual medium are selected. A process for selecting all of them as a target of secondary backup will be described with reference to a virtual medium selection process (subroutine) in FIG.

  After starting the virtual medium selection processing of FIG. 7, the CPU 12 functioning as the virtual medium automatic selection function implementing means first searches the update history field in the backup cycle storage table shown in FIG. One old virtual medium is selected as a target for secondary backup, and the backup period corresponding to the virtual medium is specified by the backup period storage table and temporarily stored (step S201).

  Then, the CPU 12 calculates the disk capacity occupied by the virtual medium, and determines whether or not the unused capacity of the magnetic disk drive 3 can be recovered to the required amount by releasing the storage area occupied by the virtual medium. Is determined (step S202).

  If it is determined that the unused storage capacity of the magnetic disk drive 3 cannot be recovered to the required amount even if only the storage area occupied by the virtual medium is released, the virtual medium continuous selection function is realized. The CPU 12 functioning as a means further searches the backup cycle field in the backup cycle storage table shown in FIG. 3, and a virtual medium having the same backup cycle as the backup cycle specified in the process of step S201 is the magnetic disk drive 3 It is determined whether or not it exists inside (step S203). When a virtual medium having the backup cycle specified in the process of step S201 exists in the magnetic disk drive 3, this virtual medium is additionally selected as a secondary backup target (step S204).

  Next, the CPU 12 functioning as the virtual medium continuous selection function realizing unit returns to the determination process in step S202 again, and releases all storage areas occupied by some of the virtual media selected so far, thereby causing the magnetic disk drive. It is determined whether or not the unused portion of the storage capacity of 3 can be recovered to the required amount (step S202), but even if all the storage areas occupied by these virtual media are released, the storage capacity of the magnetic disk drive 3 When it is determined that the unused portion cannot be recovered to the required amount, the processes of steps S203, S204, and S202 are repeatedly performed in the same manner as described above, and the unused portion of the storage capacity of the magnetic disk drive 3 is executed. Are selected one after another to restore the necessary amount to the required amount, and when the determination result in step S202 becomes true, It terminates the virtual media selection process. The virtual media backup cycles selected here are all the same.

  On the other hand, if the determination result in step S203 becomes false while repeatedly executing such processing, all virtual media having the backup cycle specified in step S201 are selected as secondary backup targets. Even if the storage area is released, the unused storage capacity of the magnetic disk drive 3 cannot be recovered to the required amount, but there is no more virtual media in the same backup cycle in the magnetic disk drive 3. To do. Therefore, in this case, the virtual medium selection is performed when all virtual media having the backup period specified in the process of step S201 have been selected as secondary backup targets, that is, when the determination result of step S203 is false. Processing will be terminated.

  If it is necessary to recover the unused amount of the storage capacity of the magnetic disk drive 3 to the required amount, the secondary backup process of FIG. 6 may be re-executed once all the processes are completed.

  If all the processes are completed and the secondary backup process is executed again after the storage area occupied by the virtual medium selected as the secondary backup target by the above process is released, the process of step S201 described above is performed. Since a virtual medium having a storage history slightly newer than the storage history specified in (2) is selected as a secondary backup target in the same processing procedure as described above, the secondary backup in FIG. By repeating the processing, it is possible to finally recover the unused portion of the storage capacity of the magnetic disk drive 3 to the required amount.

  Here, as an example, the processing in the case where a virtual medium having an old storage history is selected as the target of secondary backup has been described, but in addition to this, priority is set by setting priority for each virtual medium. It is also possible to select a secondary backup target in descending order, or to select a virtual medium at random and select a secondary backup target.

  When selecting secondary backup targets in descending order of priority, a value representing the priority is set in the update history field of the backup cycle storage table in place of the storage history described above to select a virtual medium. What is necessary is just to make it perform the process of step S201 concerned based on the low priority. In this case as well, the processing in steps S203 and S204 is performed based on the backup cycle of the virtual medium specified in step S201 in the same manner as described above. Select additional equals).

  In addition, when selecting a virtual medium at random, after selecting the first one of the virtual medium by randomly specifying a record in the backup cycle storage table by random number generation processing and integer processing instead of step S201 In the same manner as described above, the virtual media may be additionally selected based on the identity of the backup cycle in the processing of steps S203 and S204 (the backup cycle specified first in the processing of step S201 until the selection criterion of the virtual media gets tired). Is).

  When the virtual medium selection process is completed as described above, the CPU 12 executes a medium allocation process (step S102) related to selection of a magnetic tape as a storage destination of the selected virtual medium.

  Here, the specific contents of the medium allocation process will be described with reference to the medium allocation process (subroutine) in FIG.

  After starting the medium allocation process of FIG. 8, the CPU 12 functioning as the magnetic tape selection order determining function realizing unit first searches the rotation cycle storage table shown in FIG. 4 and performs the process of step S201 in the virtual medium selection process. In the magnetic tape having the same storage virtual medium period as the specified backup period, it is determined whether or not there is a magnetic tape in which a flag indicating in-use is set (step S301). If it exists, the CPU 12 functioning as the magnetic tape selection function realization means selects the magnetic tape first searched in the process of step S301 from among the magnetic tapes having the same rotation cycle as the storage destination of the virtual medium (step S302). ).

  When there is no magnetic tape in use, the CPU 12 functioning as the magnetic tape selection order determining function realization means selects one magnetic tape on which a flag indicating use is set, and the magnetic tape is selected as the magnetic tape. A flag indicating in-use is set in the status storage field of the corresponding rotation cycle storage table, and the storage virtual medium cycle of the magnetic tape is defined following the backup cycle specified in step S201 in the virtual medium selection process. After the storage virtual medium period is set in the storage virtual medium period field of the rotation period storage table corresponding to the magnetic tape (step S303), the CPU 12 functioning as the magnetic tape selection function realizing unit virtually stores the magnetic tape. Select as the storage destination of the medium (step S 04).

  When the medium allocation process is completed as described above, the CPU 12 constituting the main part of the control means 6 controls the accessor 11 to magnetically select the magnetic tape selected in the process of step S302 or step S304 in the medium allocation process. The tape is mounted on the tape read & writer 9, and the magnetic tape read & writer 9 is further driven to feed the magnetic tape to the position where the storage of the virtual medium is to be started, that is, the final record position on the magnetic tape (step S103). ), The secondary backup for storing the virtual medium selected in the processes of step S201 and step S204 in the virtual medium selection process on the magnetic tape is started (step S104).

  During execution of the secondary backup in step S104, all the virtual media selected in the processing of step S201 and step S204 in the virtual media selection processing are stored on one magnetic tape, or mounted at the present time. When the storage area of the magnetic tape is insufficient and the continuous storage of the virtual medium becomes impossible, the CPU 12 constituting the main part of the control means 6 controls the drive of the magnetic tape read & writer 9 and the accessor 11. When the magnetic tape is rewound, demounted from the magnetic tape read & writer 9 and written to the end of the magnetic tape, a flag indicating used in the status storage field of the rotation cycle storage table corresponding to the magnetic tape Is set (step S105), the secondary backup Only virtual medium completion deleted from the storage area of the magnetic disk drive 3, and release these memory areas that has stored the virtual medium and reusable state (step S106).

  Next, the CPU 12 determines whether or not all of the virtual media subject to the secondary backup are stored on the magnetic tape (step S107).

  Here, if it is determined that the storage of all virtual media that are the targets of the secondary backup is not completed, that is, the secondary backup is completed due to a shortage of the storage area of the selected magnetic tape. If not, the CPU 12 returns to the process of step S102 again, repeatedly executes the same processing operation as described above, selects another magnetic tape again and continues the secondary backup, and performs the secondary backup. Are stored across two or more magnetic tapes, and the storage area of the magnetic disk drive 3 storing these virtual media is released (steps S102 to S106).

  Finally, when it is confirmed in step S107 that the storage of all the virtual media that are the targets of the secondary backup is completed, the CPU 12 further determines that the storage capacity of the magnetic disk drive 3 is not used. It is determined whether or not the amount has been recovered to the required amount (step S108), and if the unused storage capacity has been recovered to the required amount at this time, all the processes related to the secondary backup are completed. To do.

  However, as described above, the storage capacity of the magnetic disk drive 3 is not used even if all the virtual media selected in one virtual media selection process are selected as secondary backup targets and the storage area is released. In some cases, the minute amount cannot be recovered to the required amount. In such a case, the determination result in step S108 is false.

  In this case, the CPU 12 returns to the process of step S101, repeatedly executes the same virtual medium selection process as described above, and stores a slightly new storage history as compared with the virtual medium selected in the virtual medium selection process executed first. The virtual medium having the same backup cycle as that of the virtual medium is selected again as the target of the secondary backup, and these virtual media are stored on the magnetic tape in the secondary backup process of FIG. Further free up the storage area.

  By repeatedly executing these processes until the unused amount of the storage capacity of the magnetic disk drive 3 is restored to the required amount, the determination result in step S108 is finally true and the secondary backup is performed. All processing related to is completed.

  Next, taking as an example the case where six virtual media are stored on one magnetic tape, the utilization efficiency of the magnetic tape when this embodiment is applied and the utilization efficiency of the magnetic tape when the conventional technology is applied Compare.

  FIG. 9 shows a case where the secondary backup from the magnetic disk drive 3 to the magnetic tape is performed in the order in which the virtual medium is stored in the magnetic disk drive 3 from the host device 2 regardless of the backup period of the virtual medium and the rotation period of the magnetic tape. FIG. 10 is a conceptual diagram showing the storage status of the magnetic tape, and FIG. 10 shows a magnetic tape having a storage virtual medium period corresponding to the backup period selected by selecting a virtual medium having the same backup period by applying this embodiment. It is the conceptual diagram which showed the storage condition on the magnetic tape at the time of selecting and performing secondary backup. However, the method described with reference to FIG. 5 is applied to the backup procedure.

  Here, virtual media that are not hatched in FIGS. 9 and 10 need to be left as valid data without being overwritten four weeks after the first writing from the host device 2 to the virtual medium (7). It is a virtual medium with

  In the conventional method of writing to the magnetic tape in the order in which the virtual medium is written, the virtual medium (7) is written to the magnetic tape (1), which is an empty medium. Subsequently, in order to store the virtual medium as much as possible on the magnetic tape (1), the virtual medium (1) to the virtual medium (5) are also written on the same magnetic tape (1). When six virtual media are stored, no more virtual media can be stored on the magnetic tape (1), so the virtual medium (6) is written on the magnetic tape (2). Thus, when data is stored in the order of writing, as shown in FIG. 9, a virtual medium effective for five magnetic tapes of magnetic tape (1) to magnetic tape (5) after four weeks, as shown in FIG. The data will be scattered.

  On the other hand, in the method to which this embodiment is applied, the virtual medium (7) is written on the magnetic tape (1) which is a free medium. Subsequently, since the virtual medium (1) to the virtual medium (6) have a different backup cycle from the virtual medium (7), they are written on the magnetic tape (2), which is an empty medium. Next, when the virtual medium (8) is written, the writing is performed on the magnetic tape (1) in which the virtual medium (7) having the same backup cycle as the virtual medium (8) is already written. . As described above, when virtual media having the same backup cycle are stored on the same magnetic tape, as shown in FIG. 10, data of valid virtual media is collected.

  As described above, data of effective virtual media can be collected on the magnetic tape by writing the virtual media having the same backup cycle to the same magnetic tape.

  Next, when the number of virtual media that can be stored on one magnetic tape is different, the utilization efficiency of the magnetic tape when this embodiment is applied and the utilization efficiency of the magnetic tape when the conventional technology is applied are compared.

  FIG. 11 is a graph showing the average number of magnetic tapes used when the number of virtual media that can be stored on one magnetic tape changes from 2 to 11. The solid line in FIG. 11 represents the average number of magnetic tapes used when the prior art is applied, and the broken line in FIG. 11 represents the average number of magnetic tapes used when this embodiment is applied.

  The average number of magnetic tapes used was obtained by simulating from the time when all virtual media were written to the magnetic tape until all virtual media were written to the magnetic tape at least 100 times.

  As shown in FIG. 11, when this embodiment is applied, the number of magnetic tapes used to store the same number of virtual media can be reduced as compared with the prior art.

  Next, an example in which the virtual media backup cycle is set to three types of one week, one month, and one year will be described.

  An example of the backup cycle storage table of the rotation management unit 7 when this condition is applied is shown in FIG. Since backup is performed using the virtual medium (11) to the virtual medium (22) once every four weeks, the backup period of each of the virtual medium (11) to the virtual medium (22) is one year (four weeks). Since the backup is performed using the virtual medium (7) to the virtual medium (10) once every seven days, the virtual medium (7) to the virtual medium (10) Each backup cycle is one month (four weeks with seven days as one lap). Since the virtual medium (1) to the virtual medium (6) are used for daily backup except Sunday, the backup period of each of the virtual medium (1) to the virtual medium (6) is one week.

  When such a backup procedure is adopted, the average number of magnetic tapes used when the number of virtual media that can be stored on one magnetic tape changes from 2 to 11 is shown in a graph. 13. The solid line indicates the average number of magnetic tapes used when the conventional technology is applied, and the broken line indicates the average number of magnetic tapes used when the present embodiment is applied.

  As shown in FIG. 13, according to the present embodiment, the number of magnetic tapes to be used can be greatly reduced as compared with the prior art, particularly when virtual media having greatly different backup cycles are mixed.

  Next, it will be described how the number of magnetic tapes to be used changes according to the increase / decrease in the number of virtual media when managed according to the type of backup.

FIG. 14 shows the contents of the virtual medium rotation management unit. A weekly backup is performed at a cycle of once every seven days, and [N-6] virtual media from the virtual medium (7) to the virtual medium (N) are used for the weekly backup. On days other than the day of weekly backup, day backup is performed, and six virtual media of virtual medium (1) to virtual medium (6) are used for the day backup.
FIG. 15 is a graph showing the average number of magnetic tapes used when the number of virtual media used for weekly backup is changed from 4 to 12 in this backup procedure.

  According to this embodiment, the number of magnetic tapes to be used is reduced without being greatly affected by the change in the number of virtual media allocated to the backup type, that is, the change in the number of generations managed by backup. be able to.

  Next, the control unit of the virtual magnetic tape device obtains the backup cycle for each virtual medium based on the data overwrite execution date, and manages the virtual medium selection process and magnetic tape allocation process in the secondary backup. An example will be briefly described.

  Since the hardware configuration of the virtual magnetic tape device is the same as that of the virtual magnetic tape device 1 shown in FIGS. 1 and 2, the description thereof will be omitted. In the following description, the reference numerals shown in FIGS. The processing operation unique to the present embodiment will be described with reference to FIG.

  The configuration of the backup cycle storage table provided in the virtual medium rotation management unit 7 of this embodiment is as shown in FIG. 16, and in addition to the backup cycle for each virtual medium, the latest overwrite execution date for each virtual medium. The date is memorized.

  Next, backup cycle automatic setting processing executed by the CPU 12 incorporated in the control means 6 will be described with reference to the flowchart of FIG.

  When a write command is sent from the host device 2 to the virtual medium of the magnetic disk drive 3, the CPU 12 first refers to the pointer set in the virtual medium, and the data storage start position in the virtual medium is the virtual storage medium. It is determined whether it is at the head of the storage area of the medium (step S401).

  This pointer is set at the beginning of the storage area of the virtual medium when the host device 2 starts using the virtual medium (when the virtual medium is mounted), and when data is written to the virtual medium. Is set at the end of the data written this time when the data writing is completed. Further, when a rewind command is received from the host system, this pointer is returned to the initial position, that is, the head of the storage area in the virtual medium.

  Therefore, the determination result in step S401 becomes true when the command is the first write command after receiving the virtual medium mount command from the host device 2, or after the positioning command to the head of the virtual medium such as a rewind command. This determination result is false for a write command that additionally writes after the written data.

  Therefore, the CPU 12 refers to the backup cycle storage table as shown in FIG. 16, and has the overwrite execution date already stored in the recording date field of the backup cycle storage table corresponding to the virtual medium designated as the write destination? In other words, it is determined whether this virtual medium is used for the first time or whether it is used for the second or later overwriting (step S402).

  Here, when the overwrite execution date is not stored in the recording date field and the determination result in step S402 is false, this means that the virtual medium is used for the first time, and therefore the CPU 12 determines that the virtual The current date is stored as the first overwrite execution date in the recording date field of the backup cycle storage table corresponding to the medium (step S405), and the current backup cycle automatic setting process is terminated. However, the first overwriting execution date here is actually the date when this virtual medium was used for the first time. In such a case, since it is logically impossible to calculate the backup cycle, the virtual cycle is newly reinstated unless a value is previously set in the backup cycle field of the backup cycle storage table corresponding to this virtual medium. Until the data is overwritten at the head position of the medium, the backup period of the virtual medium is indefinite.

  On the other hand, if the determination result in step S402 is true, that is, if the overwrite execution date is already stored in the recording date field of the backup cycle storage table corresponding to this virtual medium, the head of this virtual medium is stored. This means that the second and subsequent overwriting from the position is about to be performed. Therefore, the CPU 12 functioning as the backup cycle automatic setting function realizing means stores the overwrite execution date stored in the recording date field of the backup cycle storage table. The difference from the current date is obtained and used as the backup cycle of the virtual medium, and this value is set in the backup cycle field of the backup cycle storage table (step S403), and the backup cycle storage table corresponding to this virtual medium is recorded. The current date in the date field and the new overwrite date It is stored Te (step S404), and ends the current backup cycle automatic setting process.

  Next, another example of a method for calculating the backup period of the virtual medium will be briefly described. When the backup cycle of the virtual medium is already stored in the backup cycle storage table, that is, when the third and subsequent overwrites are executed, the backup cycle is calculated in step S403 by (backup cycle) = (current time Backup cycle stored in the backup cycle field × A) + [(current date−overwrite execution date currently stored in the recording date field) × (1-A)], where 0 <A You may make it perform based on the arithmetic expression of <1.

  Here, when calculating a new backup cycle, A gives priority to either the time interval from the previous overwrite execution date to the previous overwrite execution date or the time interval from the previous overwrite execution date to the current overwrite execution date. If the value of A is set small, the time interval from the previous overwrite execution date to the current overwrite execution date is strongly reflected to obtain a new backup cycle. If the value of A is set large, a new backup cycle can be obtained by strongly reflecting the first set backup cycle.

  Here, as an example, the case where the backup cycle for each virtual medium in the magnetic disk drive 3 is automatically set by the internal processing of the CPU 12 has been described. However, the rotation cycle storage table is overwritten with the field for storing the rotation cycle of the magnetic tape. A field for storing the execution date (including the first use date), and when backing up from the virtual medium in the magnetic disk drive 3 to the magnetic tape in the magnetic tape drive 5, By applying the same processing as that shown in FIG. 17 for the calculation, the rotation period for each magnetic tape in the magnetic tape drive 5 can be automatically set.

  Other processing operations in the present embodiment are the same as those in the embodiment described with reference to FIGS. 1 to 2 and FIGS.

The virtual media backup cycle and the magnetic tape storage virtual media cycle set by the processing procedure of the present embodiment are divided into a virtual media selection process in the magnetic disk drive 3 and a magnetic tape selection process in the magnetic tape drive 5. Specifically, it is used for the processing in step S203 in the virtual medium selection processing (search for the backup cycle in the backup cycle storage table) and the processing in step S301 in the medium allocation processing in FIG. 8 (search for the rotation cycle in the rotation cycle storage table). Thus, it is possible to control to write virtual media having greatly different backup cycles on different magnetic tapes.
However, when making a determination related to the selection of the virtual media to be backed up or the selection of the backup destination magnetic tape based on the backup cycle obtained by calculation, some differences in the backup cycle are the same considering the calculation error etc. It may be determined as a backup cycle.

  As described above, the virtual media backup period and the magnetic tape storage virtual medium period are obtained in the virtual magnetic tape device 1, and based on these backup periods, a virtual medium that approximates the backup period is selected, and this By selecting a magnetic tape having a storage virtual medium period corresponding to or close to the backup period and executing secondary backup, the host apparatus 2 or the management system 8 performs backup period for each virtual medium or storage virtual for each magnetic tape. It is possible to increase the reuse efficiency of the magnetic tape without setting the medium period one by one.

  In the above embodiment, the case of the virtual magnetic tape device 1 using the magnetic tape library device having one magnetic tape read & writer 9, the accessor 11, and the tape storage shelf 10 as the magnetic tape drive 5 for secondary storage will be described. However, the magnetic tape drive 5 can be constructed using a plurality of equivalent magnetic tape library devices.

  The technical idea of the present invention can also be applied to a backup device that performs tertiary or higher-order backup or a backup device that performs backup from a magnetic tape to a magnetic tape.

FIG. 3 is a functional block diagram showing a connection relationship between a virtual magnetic tape device of one embodiment to which a data backup method of the present invention is applied, a host device and a management system, and an internal structure of a virtual magnetic tape device constituting a main part. is there. Example 1 It is the block diagram which showed the outline of the structure of the control means with which the virtual magnetic tape apparatus of the Example is provided. Example 1 It is the conceptual diagram which showed an example of the backup period storage table provided in the virtual medium rotation management part of the control means with which the virtual magnetic tape apparatus of the Example is provided. Example 1 It is the conceptual diagram which showed an example of the rotation period storage table provided in the virtual medium rotation management part of the control means with which the virtual magnetic tape apparatus of the Example is provided. Example 1 It is the conceptual diagram which showed an example of the backup procedure of the virtual medium from a high-order apparatus to a magnetic disk drive. Example 1 It is the flowchart which showed the outline of the secondary backup process which CPU of the control means with which the virtual magnetic tape apparatus of the Example is provided performs. Example 1 It is the flowchart shown about the virtual medium selection process of CPU which implement | achieves a virtual medium automatic selection function and a virtual medium continuous selection function. Example 1 It is the flowchart shown about the medium allocation process of CPU which implement | achieves a magnetic tape selection function and a magnetic tape selection order determination function. Example 1 Regardless of the backup period of the virtual medium and the rotation period of the magnetic tape, the storage on the magnetic tape when the secondary backup from the magnetic disk drive to the magnetic tape is performed in the order in which the virtual medium is stored in the magnetic disk drive. It is the conceptual diagram which showed the condition. (Conventional technology) This example shows the storage status on a magnetic tape when a virtual medium having the same backup cycle is selected, a magnetic tape having a storage virtual medium cycle corresponding to the backup cycle is selected, and secondary backup is performed. It is a conceptual diagram. Example 1 It is a graph showing the average number of magnetic tapes used when the number of virtual media that can be stored on one magnetic tape changes from 2 to 11, and the solid line is the average of the magnetic tapes when the conventional technology is applied The number used is shown, and the broken line shows the average number of magnetic tapes used when this embodiment is applied. (Comparison between Example 1 and prior art) It is the conceptual diagram which showed an example of the backup period storage table of a rotation management part when the backup period of a virtual medium is made into three types, 1 week, 1 month, and 1 year. (Variation related to Example 1) It is a graph showing the average number of magnetic tapes used when the number of virtual media that can be stored on one magnetic tape changes from 2 to 11, and the solid line shows the magnetic tapes when the conventional technology is applied. The average number of used tapes is shown, and the broken line shows the average number of magnetic tapes used when this embodiment is applied. (Comparison between Modification Example Related to Example 1 and Conventional Technology) It is the conceptual diagram which showed an example of the backup period storage table of the rotation management part at the time of changing the number of virtual media allocated with respect to backup classification largely. (Another modification related to Example 1) It is a graph showing the average number of magnetic tapes used when changing the number of virtual media allocated to the backup type, the solid line represents the average number of magnetic tapes used when applying the conventional technology, The broken line represents the average number of magnetic tapes used when this embodiment is applied. (Comparison between another modified example related to Example 1 and the prior art) Backup cycle storage of the rotation management unit when the control means obtains the backup cycle for each virtual medium based on the data overwriting execution date and manages the virtual media selection processing and magnetic tape allocation processing in the secondary backup. It is the conceptual diagram which showed the structural example of the table. (Example 2) It is the flowchart shown about the backup period automatic setting process which CPU which functions as a backup period automatic setting function implementation means performs. (Example 2)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Virtual magnetic tape apparatus 2 Host apparatus 3 Magnetic disk drive 5 Magnetic tape drive 6 Control means 7 Virtual medium rotation management part 8 Management system 9 Magnetic tape read & writer 10 Tape storage shelf 11 Accessor 12 CPU (magnetic tape selection function realization means Virtual media automatic selection function realization means, virtual media continuous selection function realization means, magnetic tape selection order determination function realization means, backup cycle automatic setting function realization means)
13 ROM
14 RAM
15 Interface 16 Input / output times

Claims (10)

A magnetic disk drive for primary storage that stores data of the host device as a virtual magnetic tape medium (virtual medium) and a plurality of magnetic tapes are selectively used to convert the virtual medium of the magnetic disk drive into a magnetic tape. And storing the virtual medium of the magnetic disk drive on the magnetic tape via the magnetic tape drive, and storing the virtual disk stored in the virtual medium. In the data backup method that frees up the area and reuses it,
The host device sets a backup cycle (storage virtual medium cycle) of the virtual medium stored in each of the magnetic tapes in correspondence with a backup cycle in which data is overwritten on the virtual medium of the magnetic disk drive,
When the virtual medium of the magnetic disk drive is stored on the magnetic tape via the magnetic tape drive, the magnetic tape corresponding to the backup cycle of the virtual medium is selected and the data of the virtual medium is stored. Data backup method.   2. The virtual medium having an old storage history is selected and stored on the magnetic tape when the virtual medium of the magnetic disk drive is stored on the magnetic tape via the magnetic tape drive. Data backup method.   When the virtual medium of the magnetic disk drive is stored on the magnetic tape via the magnetic tape drive, the virtual medium having the same backup period until the storage area of the magnetic disk drive is released by a necessary amount 3. The data backup method according to claim 1, wherein the selection is continued.   When the virtual medium of the magnetic disk drive is stored on the magnetic tape via the magnetic tape drive, a magnetic tape in use is preferentially selected, and a new magnetic tape is only created when there is no magnetic tape in use. 4. The data backup method according to claim 1, wherein a tape is selected. Magnetic disk drive for primary storage that stores data of a host device as a virtual medium, and magnetic for secondary storage that selectively uses a plurality of magnetic tapes to store the virtual medium of the magnetic disk drive on the magnetic tape Drive control of the tape drive, the magnetic disk drive and the magnetic tape drive, and store the virtual medium of the magnetic disk drive on the magnetic tape via the magnetic tape drive, and store the magnetic medium stored in the virtual medium A virtual magnetic tape device comprising control means for releasing a storage area of a disk drive,
A backup cycle storage table that stores, for each virtual medium, a backup cycle in which the host device overwrites data on the virtual medium of the magnetic disk drive, a rotation cycle for each magnetic tape, and a backup of the virtual medium stored in each magnetic tape A rotation cycle storage table for storing the cycle and the control means;
The control means refers to the backup cycle storage table and the rotation cycle storage table when the virtual medium of the magnetic disk drive is stored in the magnetic tape via the magnetic tape drive, and the backup cycle of the virtual medium is referred to A virtual magnetic tape device is provided with a magnetic tape selection function for selecting a magnetic tape corresponding to the above and storing data of the virtual medium. The backup cycle storage table includes a field for storing a data overwrite execution date for the virtual medium,
When the virtual medium of the magnetic disk drive is stored in the magnetic tape via the magnetic tape drive, the control means refers to the backup cycle storage table and selects a virtual medium having an old overwrite execution date. 6. A virtual magnetic tape device according to claim 5, wherein a virtual medium automatic selection function for storing the data on the magnetic tape is provided.   When the virtual medium of the magnetic disk drive is stored in the magnetic tape via the magnetic tape drive, the control means is the same until the storage area of the magnetic disk drive is released by a necessary amount. 7. The virtual magnetic tape device according to claim 6, wherein a virtual medium continuous selection function for continuously selecting virtual media having a backup cycle is provided.   When the control means stores the virtual medium of the magnetic disk drive on the magnetic tape via the magnetic tape drive, the magnetic tape being used is preferentially selected and there is no magnetic tape being used. 8. The virtual magnetic tape device according to claim 5, wherein a magnetic tape selection order determining function for selecting a new magnetic tape is provided only for the virtual magnetic tape device.   The control means is provided with a backup cycle setting function for setting a backup cycle given from the host device in the backup cycle storage table. The virtual magnetic tape device according to claim 8. 5. The backup means is provided with a backup cycle automatic setting function for obtaining the backup cycle based on a data overwriting execution date and setting the backup cycle in the backup cycle storage table. 9. A virtual magnetic tape device according to claim 7 or claim 8.

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