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AssigneeHitachi, Ltd.
InventorsHideo Tabuchi, Akinobu Shimada, Masafumi Nozawa, Toshio Nakano
Estimating the term…
A disk subsystem assures the sequence and the coherence of data updating with two or more disk subsystems is provided with an asynchronous remote copy function. A main center 9 includes a computer system having the configuration of slave subsystems 3-2 to 3-n connected with a master disk subsystem 3-1. It secures the coherence between data at the main center 9 and the remote center 10 at the temporary suspension by repeating temporary suspension and release of the temporary suspension of the remote copy by the master subsystem 3-1 at predetermined opportunities. It also repeats temporary suspension and release of the temporary suspension of the remote copy by slave subsystems 3-2 to 3-n connected to it.
A system comprising:
A method of performing a remote copy to store data in a remote center using a slave subsystem comprising:
A subsystem that is provided with a control part that exchanges information with a host unit, a storage part that stores the information, and a transfer controller that transfers the information to other subsystems temporarily suspending the transfer at specified opportunities.
A first and a second subsystem each comprising a control part that exchanges information with a host unit, a storage part that stores the information and a transfer part that transfers the information from the host unit to another subsystem;
An integrated system comprising:
An integrated system comprising a first disk subsystem group connected with a host unit and a second disk subsystem group that receives a data transfer from the first disk subsystem group, and in which one of the disk subsystems of the first disk subsystem group is a master subsystem that controls the data transfer from the first disk subsystem group to the second disk subsystem group.
A method of preserving coherence of data that secures the coherence of data with a master subsystem by receiving data from the host unit, storing the data in a storage device and inquiring the master subsystem whether the master subsystem is in the state to transfer data to a remote center.
Dependencies are inferred from the claim text.
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Using a plurality of controllers: asynchronous techniques
By mirroring: optimisation of the communication load
Computing and data processing
Term end not estimated
This invention relates to external storage units which store data for a computer system, as well as to an integrated system of such external storage units, The invention also relates to remote copy technology to duplicate data among external storage units without need of a host computer connecting external storage unit groups located at distant places with other external storage unit groups. A group of storage units (subsystem) includes a controller that exchanges information with a host unit and a storage unit that is integrated with a disk drive for storing data.
To provide reliable backup of data in a natural disaster such as an earthquake, the distance between a main center and remote centers is typically from 100 km to several hundreds kilometers. For this purpose, several external storage systems provided with a remote copy function that duplicate and store the data among subsystems at a main center and a remote center are used. Such remote copy functions can be separated into two categories—a synchronous type and an asynchronous type.
A synchronous remote copy procedure is one that when a data update (write) instruction is issued from a host computer at the main center to a subsystem and the object of the instruction is a remote copy function, the completion of update processing is reported to the host unit at the main center after the data update (writing) is completed at the remote subsystem. In this case, there is a delay time (transmission time etc.) corresponding to the geographical distance between the main center and the remote center, and the delay can be influenced by the performance of data transmission lines between the main center and the remote center.
FIG. 1 is a diagram that illustrates the configuration of a remote copy system of a preferred embodiment of the present invention;
FIG. 2 is a flow chart that illustrates the operation of a remote copy system;
FIG. 3 is a flow chart that further illustrates the operation of a remote copy system; and
An example of a preferred embodiment of the present invention applied to a computer system is described below. FIG. 1 is an example of configuration of the application of the present invention for duplicating information (data) between an arbitrary pair of centers at two or more data centers equipped with computer systems.
Connecting one or more units of disk subsystems 3 on the side of a main center 9 with one or more units of disk subsystems 7 on the side of a remote center 10 without the intervention of a host computer 1 and 8, a remote copy system that duplicates data between the centers is provided. An example of a connection of disk subsystems operating without the intervention of host unit, for example, is an SAN (Storage Area Network). FIG. 4 shows an example of the configuration of the disk subsystem 3 at the main center 9.
In the main center 9 of FIG. 1, a host unit 1, equipped with a central processing unit (CPU), that executes data processing is connected with a disk subsystem 3-1 (a master subsystem) and disk subsystems 3-2 . . . 3-n (slave subsystems) through an interface cable 2 that provides a transmission path.