Method for backing up a disk array system

A method for backing up the data of a disk array system having network file server and storage area network functions easily and rapidly without using a route for data to be not backed up. Upon receipt of a backup request, a network file server module copies files on the disk array system's regular volumes to a backup volume. The network file server module then requests a storage area network module to copy the files to an external storage device. Finally, the storage area network module copies the current contents of the backup volume to the external storage device. The network file server module can limit the data to be backed up, thereby reducing the backup time requirements. The load on a LAN does not increase because the storage area network module acquires the data to be backed up. The processing speed increases thanks to backup load distribution within the disk array system.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to U.S. patent application Ser. No. 10/020,313 filed on Dec. 18, 2001, entitled “Storage System, a Method of File Data Backup and a Method of Copying of File Data,” the disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a disk array system, and more particularly to a control method for backing up its data to an external device.

For backing up the data of a disk array system, a differential backup method can be used to prevent the size of backup data from being enormously increased.

Using a file basis differential backup method for a disk array system having a network file server function and a storage area network function increases the load on a local area network that is used for data exchange during regular operation by host computers. Because the storage area network function cannot specify files and the network file server function has to be used for the method. In some cases, it is necessary to make a backup while regular operations implemented by the network file server function are halted.

Meanwhile, the disk array system having the network file server function and storage area network function uses a technology called “NAS over SAN”. When this technology is used, the data passing through a local area network is limited to file names, file attributes, and other items of file information, and the data contained in files are exchanged via a storage area network. When a backup is made with this technology, the backup data and the data exchanged for regular operations both pass through a storage area network.

In a system described in JP-A No. 112669/2000, a disk unit is provided with an area for temporarily storing backup data for the purpose of adjusting the speeds of the disk unit and external backup storage. This area does not store part of backup data and cannot possibly reduce the size of backup data.

In a system described in JP-A No. 347811/2000, a volume of a disk unit is made redundant for data storage purposes. This system can back up data within the disk unit. However, if the data is to be transferred out to an external device, the size of backup data does not decrease.

SUMMARY OF THE INVENTION

The present invention aims at providing a means of easily making a rapid backup of a disk array system having a network file server function and storage area network function using a path separate from those for non-backup data and without increasing the load on a local area network.

Files to be backed up are dispersed to two or more volumes of a disk array system.

In one aspect of the invention, the network file server function is first exercised to select the files to be backed up on an individual file basis and copy them onto a specific backup volume (primary backup). Next, the storage area network function is notified of the termination of the primary backup process. Upon receipt of such a notification, the storage area network function copies the backup volume to an external storage device to complete the backup process.

More specifically, a correlation table is created in the above-mentioned primary backup sequence to indicate copy-source disk volumes to which the individual files to be retained on the backup volume belong. Typically, the correlation table is also stored as a file on the backup volume. That is, the correction table is copied to an external storage device together with backup files when a backup is made by the storage area network function.

Typically, restoration of backup data is achieved by reversing the above-mentioned backup steps. That is, restoration data stored in an external storage device is entered in the disk array system by the storage area network function. In this instance, the disk array is provided with a specific restoration volume, which stores the whole restoration data. Next, the backups of individual files contained in the restoration data are copied to the original disk volumes by the network file server function. The restoration process is then completed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1diagrammatizes the disk array system structure and backup operation according to one embodiment of the invention.

A disk array system1has a network file server module2, which is connected to a local area network5, and a storage area network module3, which is connected to an external storage device9via a storage area network8. Both of these modules can access disk volumes10and11. In addition, a backup disk volume12is formed for use in data backup and data restoration. Direct communication can be established between the network file server module2and storage area network module3through an inter-module communication function4. The local area network5is connected to a management computer6that manages the disk array system1and a host computer7. Typically, a magnetic tape storage device, magneto-optical disk storage device, or other storage device is used as the external storage device9.

The subsequent explanation presumes that the disk array system has one unit each of the network file server module2and storage area network module3. However, the number of units does not have to be limited at1. The invention is also applicable to situations where the disk array system1has two or more units each of the network file server module2and storage area network module3.

The subsequent explanation also presumes that the inter-module communication function4provides direct communication within the disk array system1. However, the invention is also applicable to situations where the employed communication function provides communication via a device external to the disk array system1or via a network.

In the system shown inFIG. 1, the disk data is backed up onto an external storage device9in the following sequence:

Typically, a backup operation starts when a management computer6issues a backup request to the disk array system1. The backup request is forwarded to a network file server module2of the disk array system1via the route indicated by the reference numeral101inFIG. 1, that is, a local area network5. The backup request reports the specified files to be backed up14, the specified backup volume12, and other conditions.

Note that the files to be backed up14are not always specified by a backup request issued by the management computer6. The file for specifying the files to be backed up (backup correlation table) may be provided on a volume of the disk array system1and used to specify the files to be backed up. In this instance, the backup request issued by the management computer6specifies the name of the file that carries the backup correlation table. The network file server module2, which receives the backup request, reads the specified backup correlation table and specifies the files to be backed up. When these two methods of specifying the files to be backed up are made available, the disk array system can be flexibly operated.

Further, the backup of the disk array system1can be alternatively started, for instance, at fixed intervals specified by a timer, not shown, which is provided inside the disk array system1, or directly by the network file server module2, without being triggered by the receipt of a backup request from an external computer6or7, which is connected to a local area network5.

Upon receipt of a backup request, the network file server module2copies the files14specified by the backup request to a backup volume12specified by the backup request. In this instance, the module stores the correlation between the copied files and their respective copy source disk volumes in the correlation table15on the backup volume12. This correlation storage operation is indicated by the reference numeral102inFIG. 1. This copy operation concludes the primary backup process.

Note that the term “backup volume12” does not always represent one disk volume. Two or more disk volumes can be used as backup volumes12. Further, a virtual volume can be used as a backup volume12. Furthermore, a backup volume12can be created within a memory.

When the specified files14are completely copied to the backup volume12(primary backup), the inter-module communication function4sends a copy request103from the network file server module2to the storage area network module3. This copy request103requests that the backup volume be copied to an external storage device.

Upon receipt of the request for copying the backup volume12to the external storage device9, the storage area network module3copies the backup volume12to the external storage device9via the storage area network8. In this instance, the correlation table15on the volume12indicates the locations of the disk volumes on which the files stored on the backup volume12were originally stored. When the backup volume12is copied to the external storage device9, the correlation table15is also copied to the external storage device9. The reference numeral104inFIG. 1indicates the route over which the copy operation is performed. When this copy operation ends, the secondary backup process is completed for the specified files14.

The above disk data backup is performed over a route other than the local area network5, which is used for disk access from the host computer7and other regular operations of the disk array system1. Therefore, the backup can be completed while the influence upon regular operations is minimized. Further, the backup data size will not unduly increase because the backup target can be specified on an individual file basis.

The request for copying the backup volume12to the external storage device9does not always have to be issued at the end of each file copy operation performed for the backup volume12as described in the above third backup step. The request for copying can be issued in some modified ways. For example, the request can be issued in accordance with the size of the file data copied to the backup volume12, issued in compliance with a backup request received by the network file server module2, or issued in accordance with a timer in the disk array system1. These modifications will reduce the number of times the backup data is to be copied to the external storage device9.

When specified files are completely copied to the backup volume12, the backup of these files is saved within the same disk array system. In other words, the data on the backup volume12may be valid for restoration if the file data in disk volumes10and11is damaged.

The number of external storage device9to which the backup volume12is to be copied should not be limited at1. The backup volume12can be copied to each of two or more units of the external storage device or divided into segments and then copied separately to two or more units of the external storage device.

The data restoration procedure of one embodiment of the invention is described below with reference toFIG. 2.

As indicated by the reference numeral201inFIG. 2, a network file server module2of a disk array system1receives a restoration request from a disk array system management computer6connected to a local area network5. The restoration request conveys information such as a specified external storage device having the data to be restored and a specified restoration volume12.

The restoration request does not always have to be received from the disk array system management computer6connected to the local area network5. The request can also be issued by the network file server module2, which retains the information about the external storage device9and restoration volume12beforehand.

When two or more units of the external storage device9are connected to a storage area network, the restoration request specifies the external storage device9that retains the data to be restored. However, the external storage device9should not always be specified by the restoration request. The network file server module2can retain the data to be restored on accessible regular volumes10,11and reference it for restoration purposes.

The network file server module2requests the storage area network module3to copy to the volume12the restoration data that is backed up on the external storage device9connected to the storage area network8. The route of this request is indicated by the reference numeral202inFIG. 2. The volume12may be different from or identical with the backup volume indicated inFIG. 1. The example inFIG. 2presumes that the volume12is identical with the backup volume indicated inFIG. 1. That is why the same reference numeral is used in these two figures.

Upon receipt of a request from the network file server module2, the storage area network module3copies the restoration data to the volume12from the external storage device9, which is connected to the storage area network8. The data contains the specified volume data and the correlation table15, which shows the correlation between the specified volume data and the volumes on which the files containing the specified volume data existed. The route for this data copy operation is indicated by the reference numeral203inFIG. 2.

More specifically, the backup data copied to the external storage device9as explained with reference toFIG. 1are generally accumulated upon each backup. Meanwhile, the backup volume12can store only the latest backup data because it is repeatedly used for backup. When the volume12still stores the data to be restored, the data need not be copied from the external storage device9to the volume12for restoration purposes. The data stored on the volume12should be used directly for restoration. In such a situation, the second and third restoration steps are skipped. Further, the restoration data does not always have to be copied to the disk unit's restoration volume12. It can be copied into the disk array system l's memory as a virtual volume.

The restoration data recorded in the external storage device9is copied to the disk array system1via the storage area network8. Therefore, such a copy operation does not obstruct regular data transfer operations of the local area network5.

The storage area network module3exercises the inter-module communication function4to notify the network file server function2that the volume data is completely copied to the restoration volume12. The route for this notification is indicated by the reference numeral204inFIG. 2. Instead of the inter-module communication function4, a communication function external to the disk array system1or the connection between the storage area network module and local area network5can be used to effect communication.

Upon receipt of the notification that the restoration data has been completely copied to the volume12, the network file server module2copies the copied files on the volume12to regular volumes10,11. The correct correlation between the files and their respective copy destination regular volumes is established by reading the correlation table15, which is contained in the restoration data copied from the external storage device9. The route for copying to the regular disk volumes is indicated by the reference numeral205inFIG. 2.

The destinations of the restoration files do not always have to be determined by the correlation table15on the restoration volume. For example, the network file server module2can retain the correlation table15, which shows the destinations of restoration files, on the accessible regular disk volumes10,11and use it for restoration, or attach the correlation table15to the restoration request to indicate the destinations of restoration data.

When the correlation table15is used to indicate the destinations of restoration data, predesignated files can be automatically restored. Further, when the correlation table15is attached to a restoration request to indicate the destinations of restoration data, it is possible to restore specific files only.

FIG. 3is a flowchart describing a typical backup process according to the above-mentioned preferred embodiment. The backup steps are described sequentially below:

A backup process starts when the management tool of the disk array system transmits a backup request (step301).

A process existing in the network file server module is waiting for a backup request. The backup request is received by this process (step302).

The files to be backed up are selected in compliance with the request received by the network file server module (step303).

The network file server module copies the selected files to the backup volume (step304).

When the copy operation ends, the network file server module issues a volume backup request to the storage area network module (step305).

The storage area network module receives the volume backup request (step306).

In compliance with the backup request, the storage area network module selects a backup volume and external storage device (step307).

The storage area network module copies the backup volume to the external storage device (step308).

FIG. 4is a flowchart describing a typical restoration process according to the above-mentioned preferred embodiment.

A restoration process starts when the management tool of the disk array system transmits a restoration request (step401).

The network file server module receives the restoration request (step402).

In compliance with the received restoration request, the network file server module selects an external storage device having a specified file backup and a restoration volume within the disk array system (step403).

A request for restoring the file backup from the selected external storage device to the restoration volume is transmitted from the network file server module to the storage area network module (step404).

The storage area network module receives this restoration request (step405).

In compliance with the received restoration request, the storage area network module copies the backup data in the external storage device to the restoration volume (step406).

When the data copy operation ends, the storage area network function notifies the network file server that the data has been completely copied to the restoration volume (step407).

The network file sever receives the copy process termination notification (step408).

The network file server copies the backup data on the restoration volume to a separate volume (step409). Data restoration is then completed.

When a backup scheme and restoration scheme are created in this manner with the information about the files to be backed up and restored, the backup and restoration processes for a disk array system can be automatized.

In the preferred embodiment described above, data is backed up onto an external storage device via the storage area network module3, which is connected to the storage network8. In other words, the disk volume copy operation can be performed without regard to the local are network5, which is used for data exchange during regular operations of the host computer7. However, a function for connecting to the external storage device9can also be used, instead of the storage area network module3, to achieve data backup and restoration without increasing the load on the local area network5. For example, the adopted configuration may use a function for connecting to the external storage device via a local area network other than the local area network5that is connected to the network file server module2.

The disk array system of the invention can reduce the time required for backup because the data to be backed up can be limited by its network file server function. It also uses its storage area network function to acquire the data to be backed up, thereby reducing the load on the local area network. In addition, the network file server function and storage area network function distribute the load within the disk array system, which results in an increase the processing speed.

The foregoing invention has been described in terms of preferred embodiments. However, those skilled, in the art will recognize that many variations of such embodiments exist. Such variations are intended to be within the scope of the invention and the appended claims.