Abstract: A storage control device provided in a storage control system reports a virtual storage capacity value stored in a shared memory, to a host terminal, and ensures that, after the virtual storage capacity value has been stored in the host terminal, the virtual storage capacity value thus reported cannot be changed while the virtual storage unit having the virtual storage capacity value is connected to the host terminal.

Abstract: A method and apparatus which provide solutions for avoiding journal overflow in after and before journal methods of a backup and recovery system used with a storage system. The after journal method solutions, which are conducted when the amount of free space reaches a threshold, include periodically taking a new snapshot and deleting the oldest journal, periodically taking a new logical snapshot and deleting the oldest journal, stopping the taking journal entries when the journal volume is full, and stopping the taking journal entries when the journal volume is full and then switching to bitmap management. The before journal method solution, which is conducted when the amount of free space reaches a threshold, includes applying wrap-around overwriting to overwrite the oldest journal entry by the newest journal entry.

Abstract: A method and apparatus for transferring data between storage systems including a first disk system for receiving first data in a variable length data format from a host, storing the first data and sending the first data over an I/O channel for data in the variable length data format, a second storage system for receiving the first data from the first storage system, converting the first data from the first storage system to second data in a fixed block data format and sending the second data over an I/O channel for data in the fixed block data format, and a third storage system for receiving the second data from the second storage system, converting the second data from the second storage system back to the first data and storing the first data.

Abstract: A storage control device provided in a storage control sub-system reports a virtual storage capacity value stored in a shared memory, to a host terminal, and ensures that, after the virtual storage capacity value has been stored in the host terminal, the virtual storage capacity value thus reported cannot be changed while the virtual storage unit having the virtual storage capacity value is connected to the host terminal.

Abstract: A continuous update method includes reading out data from a first data store via a data switch to satisfy client requests for data. A second data store is updated via the data switch to contain new updated information. When it is desired to satisfy client requests with the new data, the second data store is copied to a third data store and subsequent client requests are satisfied from the third data store. Further updates are made to the second data store. The process is repeated, but the roles of the third and first data stores are reversed. In another embodiment of the invention, subsequent client requests are satisfied from the second data store and further updates are made to the first data store.

Abstract: A remote copy system includes a first storage system including a first storage controller and a first data volume. The first storage controller is configured to control data access requests to the first data volume. The first storage system is configured to store write data in the first data volume upon receiving a write request from a first host associated with the first storage system and generate a journal including control data and journal data. A second storage system includes a journal volume and configured to receive and store the journal generated by the first storage system in the journal volume. A third storage system includes a second data volume and configured to receive the journal from the second storage system and store the journal data of the journal to the second storage system according to information provided in the control data.

Abstract: Two data centers located in the vicinity are connected using a synchronous transfer copy function, and one of the data centers is coupled with a third data center disposed at a remote location by an asynchronous remote copying function. The order whereat a storage sub-system located in the vicinity has received data from a host is consistently guaranteed, and the third data center holds the data. Further, each storage sub-system includes a function whereby, during normal operation, data can be exchanged and the data update state can be obtained by the storage sub-systems located in the two data centers that do not directly engage in data transmission.

Abstract: A method and apparatus which provide solutions for avoiding journal overflow in after and before journal methods of a backup and recovery system used with a storage system. The after journal method solutions, which are conducted when the amount of free space reaches a threshold, include periodically taking a new snapshot and deleting the oldest journal, periodically taking a new logical snapshot and deleting the oldest journal, stopping the taking journal entries when the journal volume is full, and stopping the taking journal entries when the journal volume is full and then switching to bitmap management. The before journal method solution, which is conducted when the amount of free space reaches a threshold, includes applying wrap-around overwriting to overwrite the oldest journal entry by the newest journal entry.

Abstract: A storage control apparatus is coupled to a central processing unit (CPU) and a storage unit to control input/output of data between the CPU and the storage unit. The storage control apparatus has at least two processors coupled to the CPU and the storage unit, a cashe memory (CM) unit for temporarily storing data of the storage unit, a shared memory (SM) unit for storing information concerning control of the CM unit and the storage unit, and a selector coupled to the at least two processors, the CM unit and the SM unit through access paths to selectively apply access requests from the at least two processors to the CM unit and the SM unit.

Abstract: In a storage system, a logical volume is divided into a plurality of small areas called logical storage devices and only such an area designated by a user is made an object of remote copying or migratory copying. Also, there is provided a unit for forming a logical volume from any logical storage device of any RAID group. Thereby, the reduction of the deterioration in performance at the time of remote copying, the reduction of a storage area to be assigned to a secondary site as a copy destination, the shortening of a time required for migratory copying and the assignment of any area of a logical volume on any RAID group are enabled.

Abstract: A storage system maintains a journal of journal entries and at lease one snapshot of one or more data volumes. By assigning a unique sequence number to journal and snapshot, it is easy to find a journal which can be applied to the snapshot. A technique is described for detecting an overflow condition of running out of journal space and recovering the journal space.

Abstract: A remote copy system includes a first storage system including a first storage controller and a first data volume. The first storage controller is configured to control data access requests to the first data volume. The first storage system is configured to store write data in the first data volume upon receiving a write request from a first host associated with the first storage system and generate a journal including control data and journal data. A second storage system includes a journal volume and configured to receive and store the journal generated by the first storage system in the journal volume. A third storage system includes a second data volume and configured to receive the journal from the second storage system and store the journal data of the journal to the second storage system according to information provided in the control data.

Abstract: The present invention provides techniques for managing storage based replication. Specific embodiments provide techniques for performing system backup and restoring. In specific embodiments, benefits such as keeping a remote mirror between a primary volume and a secondary volume in operation can be provided. Since the remote mirror is usually used for disaster recovery purposes, where the mirrors must be always in-sync state, being able to take a backup without breaking the remote mirror can help provide a constant duplicate copy of production information in case of emergency, for example. Further, in some embodiments, a user can take backups of more than one generation by setting up two or more secondary volumes (SVOLs) for one primary volume (PVOL).

Abstract: The present invention provides techniques for managing storage based replication. Specific embodiments provide the capability to make multiple remote copies of information without the necessity of copying information for each pair, for example. One or more remote mirror pairs can be created for disaster recovery, testing, or other purposes.

Abstract: A method of performing an initial copy procedure in a remote copy system, the method including: configuring a network path between a first disk subsystem and a second disk subsystem to increase the speed of data transmission across the network path; configuring the remote copy system for a remote copy operation; performing an initial copy operation to copy data across the network path from the first disk subsystem to the second disk subsystem; and adjusting the network path to reduce the speed of data transmission across the network path. A remote copy system, including: a first disk subsystem located at a first site; and a second disk subsystem capable to be coupled to the first disk subsystem via a network path, with the network path capable to be configured to increase or decrease the speed of data transmission from the first disk subsystem to the second disk subsystem.

Abstract: Provided is a storage control system in which a number of storage controllers are connected, and restored data is forwarded from one storage controller to the other storage controller. With this storage control system, even when the host system accesses the logical volume of the forwarding destination of the restored data, the host system will be able to reliably access the restored data.

Abstract: A storage control system judges whether the data pattern of data exchanged with a higher-level device (hereafter “data”) conforms to one or a plurality of write-excluded data patterns comprised in write-excluded data pattern information prepared in advance. If a negative judgment result is obtained, the storage control subsystem stores the data in a logical device formed on a disk storage device. If, on the other hand, a positive judgment result is obtained, the storage control subsystem erases the data without storing in a logical device.

Abstract: A data sharing method for use in a computer system provided with a first computer, a second computer and a data storage subsystem for connection with the first and second computers is disclosed. The data storage subsystem has a plurality of memory units and a control unit for controlling the plurality of memory units. The control unit forms a paired state of a first memory unit storing data for use by the first computer and a second memory unit, the paired state being so controlled as to match the contents of the first memory unit and those of the second memory unit. When data used by the first computer are to be used by the second computer, the control unit releases the paired state between the first memory unit and the second memory unit to stop updating of the first memory unit to be reflected in the second memory unit.

Abstract: A storage system maintains a journal of journal entries and at least one snapshot of one or more data volumes. By assigning a unique sequence number to journal and snapshot, it is easy to find a journal which can be applied to the snapshot. A technique is described for detecting an overflow condition of running out of journal space and recovering the journal space.

Abstract: Two data centers located in the vicinity are connected using a synchronous transfer copy function, and one of the data centers is coupled with a third data center disposed at a remote location by an asynchronous remote copying function. The order whereat a storage sub-system located in the vicinity has received data from a host is consistently guaranteed, and the third data center holds the data. Further, each storage sub-system includes a function whereby, during normal operation, data can be exchanged and the data update state can be obtained by the storage sub-systems located in the two data centers that do not directly engage in data transmission.