Abstract: Provided is a method of managing differential snapshots in a storage system, the storage system having a disk drive and a disk controller, the differential snapshot management method including the steps of: providing a storage area of the disk drive as a plurality of logical volumes including an operational volume and a differential volume; storing a time of update for each block in the operational volume; and judging, upon reception of a request to write in a block included in the operational volume, whether to copy data of the block in which requested data is to be written in accordance with the received write request to the differential volume, based on the time of update of the block in which requested data is to be written and a time of creation of the differential snapshot. Accordingly, it is possible to manage the differential snapshot without using a bitmap.

Abstract: A technique for realizing a snapshot function is provided, which can reduce data transfer between a server system and a storage subsystem which is necessary during data copy operations between storage devices and reduce the degradation of data access performance of the storage device in operation. In a storage system, a command processed by a CPU of a storage subsystem includes a COPY and WRITE command for performing a data copy process and a data storage process in accordance with a predetermined sequence, and a server system issues the command to the storage subsystem. After receiving the command, the storage subsystem executes a data copy process from a first disk drive to a second disk drive, and subsequently executes a data storage process to the first disk drive, thereby keeping a snapshot of the data stored in the first disk drive.

Abstract: An application processing system including a database server and a storage device which is connected with a standby application processing system including a secondary database server and a secondary storage device to continue to carry out application processing in the case of a fault, disaster, etc. or for maintenance. The storage device of the application processing system issues a log disk update request to the secondary database server of the standby system to update a log disk of the standby system and thereby create a duplicate of the log disk for the DBMS of the application processing system. This allows the DBMS of the standby system to roll forward the log data in the duplicated log to update duplicated data on the secondary storage device.

Abstract: A hitless switching system includes a sending apparatus and a receiving apparatus. The sending apparatus includes: a distributing part for dividing an original signal into a plurality of signals; and a transmitting part for transmitting the divided signals over one or a plurality of transmission lines with redundancy. The receiving apparatus includes: a phase difference detection part for detecting phase differences between signals sent from the sending apparatus; a phase difference absorbing part for absorbing phase differences detected by the phase difference detection part; selectors each of which selects one signal from a plurality of signals; and a restoring part for restoring the original signal from the signals output from the selectors.

Abstract: An application processing system including a database server and a storage device which is connected with a standby application processing system including a secondary database server and a secondary storage device to continue to carry out application processing in the case of a fault, disaster, etc. or for maintenance. The storage device of the application processing system issues a log disk update request to the secondary database server of the standby system to update a log disk of the standby system and thereby create a duplicate of the log disk for the DBMS of the application processing system. This allows the DBMS of the standby system to roll forward the log data in the duplicated log to update duplicated data on the secondary storage device.

Abstract: The storage system includes a disk drive and a processor, the processor serving as a file system input/output processing unit and a block input/output processing unit. In the storage system, the block input/output processing unit provides, to the file system input/output processing unit, storage areas of the disk drive as plural volumes including a first volume, a second volume, and a third volume, the second volume storing a block write history, the third volume storing replication data of the first volume at a specific time. The block input/output processing unit refers to the block write history in the second volume to overwrite the replication data in the third volume with replication data of the first volume being at a different time from the specific time. The block write history in the second volume further includes information about which block is associated with which file.

Abstract: To improve snapshot performance and copying performance on a block device level in a capacity of an allocation-on-use volume. Provided is a storage system coupled to a network includes one or more volumes constituted of a plurality of blocks. The plurality of blocks include a first block and a second block, and a physical storage area is allocated to at least one of the plurality of blocks. When it is judged that the physical storage area has not been allocated to the target first block of a received writing request, the storage system writes data to be written by the writing request in the first block without copying data stored in the first block to the second block.

Abstract: Provided is a technique which solves a problem of a long-time reduction in a service level after service restoration and a problem of a failure caused by a disk capacity shortage during primary volume restoration. According to the technique, reference is made to a differential block management unit (217) setting which of a differential volume (142) and a primary volume (141) a data block of a restoring source snapshot volume (VVOL No. 3) is to determine which of the primary volume (141) and the differential volume (142) a volume storing read data is. When a restoring target data block is in a differential volume (142), data of the differential volume (142) is restored in the primary volume (141). Upon accessing to the primary volume (141) while restoring, switching is made to a virtual primary volume after restoration where data of the primary and differential volumes are combined based on the snapshot volume (VVOL No. 3) to execute accessing.

Abstract: 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.

Abstract: The reduction of the volume capacity necessary to copy the snapshot can be achieved. When an operation volume is updated, the data before the update is saved in a difference storing volume, and the data of the two volumes, that is, the operation volume and the difference storing volume are combined to constitute the snapshot. In order to constitute the snapshot, the data necessary to constitute the snapshot is copied to the snapshot saving volume by using the block copy management table in which the data location in the operation volume and the difference storing volume is recorded, and another block copy management table for retaining the data location after the copy is saved in the volume. The saved snapshot can be referenced by accessing the snapshot saving volume, to which the data constituting the snapshot is copied, by using the snapshot read program.

Abstract: A technique for realizing a snapshot function is provided, which can reduce data transfer between a server system and a storage subsystem which is necessary in data copy in storages and reduce the degradation of data access performance of the storage in operation. In a storage system, a command processed by a CPU of a storage subsystem includes a COPY and WRITE command for performing a data copy process and a data storage process in accordance with a predetermined sequence, and a server system issues the command to the storage subsystem. After receiving the command, the storage subsystem executes a data copy process from a first disk drive to a second disk drive, and subsequently executes a data storage process to the first disk drive, thereby keeping a snapshot of the data stored in the first disk drive.

Abstract: An application processing system including a database server and a storage device which is connected with a standby application processing system including a secondary database server and a secondary storage device to continue to carry out application processing in the case of a fault, disaster, etc. or for maintenance.

Abstract: 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.

Abstract: A hitless switching system includes a sending apparatus and a receiving apparatus. The sending apparatus includes: a distributing part for dividing an original signal into a plurality of signals; and a transmitting part for transmitting the divided signals over one or a plurality of transmission lines with redundancy. The receiving apparatus includes: a phase difference detection part for detecting phase differences between signals sent from the sending apparatus; a phase difference absorbing part for absorbing phase differences detected by the phase difference detection part; selectors each of which selects one signal from a plurality of signals; and a restoring part for restoring the original signal from the signals output from the selectors.