Electrical computers and digital processing systems: memory – Storage accessing and control – Control technique
Reexamination Certificate
2001-02-13
2003-10-21
Kim, Matthew (Department: 2186)
Electrical computers and digital processing systems: memory
Storage accessing and control
Control technique
C711S161000, C711S154000, C711S114000, C711S100000
Reexamination Certificate
active
06636954
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a technology of copying data stored in a plurality of areas on one logical disk to another logical disk. More particularly, this invention relates to a technology which allows a plurality of generations to be retained in a logical disk efficiently, and allows the data to be copied quickly into another medium.
BACKGROUND OF THE INVENTION
Conventionally, as a data copying technique in a logical disk such as a RAID apparatus, there exist
(1) a separate dual volume technique,
(2) a log structured file technique,
(3) a concurrent copy technique, and
(4) Japanese Patent Application No. 11-279678 applied on Sep. 30, 1999 by Fujitsu Ltd.
In case of the separate dual volume technique, when the RAID apparatus accepts a copy instruction from a host, a copy destination volume (logical disk) is prepared, and when the RAID apparatus accepts a duplication starting instruction from the host, copying from a copy source logical disk to a copy destination logical disk is started so that duplication is executed. Further, the RAID apparatus accepts a separate instruction from the host, it separates both the logical disks so that the copy source logical disk and the copy destination logical disk can be used from separate hosts.
In the log structured file technique, actual data are not copied but data in appearance are copied by pointer setting. For example, when data blocks of logical disks A, B and C are stored in one physical disk, the respective logical disks A, B and C are defined by a pointer of data in the physical disk and at the time of copying from the logical disk A to the logical disk B, a pointer of the logical disk A is set as a pointer of the logical disk B.
In the concurrent copy technique, when copying from a copy source logical disk to a copy destination logical disk is executed, a host reads data from the copy source disk and writes the data into the copy destination disk by a data transfer function. At this time, a bit map of a corresponding address of the copied data is set as “copied”.
In Japanese Patent Application No. 11-279678, even during data copying, a copy destination logical disk can be accessed. More concretely, a response of copy completion is returned immediately according to a copy instruction, and an access is accepted while actual data are being copied, and copy source and copy destination logical disks are accessed to be referred to and be updated.
However, in case of the separate dual volume technique, a duplication creating instruction should be given before the copy instruction, and a dual state should be completed. Moreover, when a plurality of generations are retained, unchanged areas between the generations are copied in an overlapped state. For this reason, there arises a problem that space efficiency is low.
Furthermore, in case of the log structured file technique, the space efficiency is the highest at the time of retaining a plurality of generations. On the contrary, since areas which were not changed in the copy source and copy destination logical disks are used in common physically, when a disk damage occurs in the commonly used areas, the copy destination logical disk cannot be accessed. For this reason, there arises a problem that a data integrity level is low (safety is low).
Furthermore, in case of the concurrent copy technique, there arises a problem that a copy destination logical disk cannot be accessed during copying process. Moreover, when a plurality of generations are retained, areas which were not changed between the generations are retained in an overlapped state. For this reason, there arises a problem that the space efficiency is low.
The invention of Japanese Patent Application No. 11-279678 solves the problem of the separate dual volume technique that pre-process is required before the copy instruction and the problem of the concurrent copy technique that a copy destination logical disk cannot be accessed during the copying process. However, when a plurality of generations are retained, areas which were not changed between the generations are retained in an overlapped state, and thus there arises a problem that the space efficiency is low.
Particularly when data retained in a logical disk are copied and retained in another external medium in order to heighten safety, copy time is required in proportion to data amount. For this reason, if areas which were not changed between the generations are copied in the overlapped state, not only the space efficiency becomes low but also enormous copy time is required.
Accordingly, the extremely important problems are how to prevent the lowering of the space efficiency in the case of retaining a plurality of generations in a logical disk and how to shorten the enormous copy time required at the time of copying and retaining into another medium.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and apparatus which allow a plurality of generations to be retained in a logical disk efficiently, and also allows the data to be copied quickly into another medium. It is an another object of the present invention to provide a computer-readable recording medium which stores a computer program which, when executed on a computer, realizes the method according to the present invention.
The inter-logical disk copy processing apparatus according to one aspect of the present invention comprises an aggregation copying unit which aggregately copies differential data stored in a plurality of areas discretely existing on the copy source logical disk to a continuous area on the copy destination logical disk; and an access processing unit which, when a request to access to the copy source logical disk or copy destination logical disk is generated during the aggregation copying process by the aggregation copying unit, stopping the aggregation copying process by the aggregation copying unit and executing an accessing process.
According to the above-mentioned aspect of this invention, the differential data stored in the plurality of areas discretely existing on the copy source logical disk are aggregately copied to the continuous area on the copy destination logical disk, and when the request to access to the copy source logical disk or copy destination logical disk is generated during the aggregation copying process, the aggregation copy process is stopped and the accessing process is executed. For this reason, a plurality of generations can be retained efficiently in a logical disk, and data can be copied to be retained quickly to another external medium.
The aggregation copying unit may be constituted so as to select a plurality of areas on the copy source logical disk to be copy target based on update history information showing updating histories of the copy source logical disk and forcible copy position information showing that forcible copying is instructed from an external apparatus.
According to this structure, a plurality of areas on the copy source logical disk to be copy target are selected based on the update history information showing updating histories of the copy source logical disk and the forcible copy position information showing that forcible copying is instructed from an external apparatus. For this reason, the areas specified externally can be included in the copy targets.
Furthermore, the aggregation copying unit may be constituted so as to calculate logical OR of the update history information in which the area positions of the copy source logical disk have one to one correspondence to bit positions and forcible copy position information so as to create copy target information, and manages areas to be copied based on the created copy target information.
According to this structure, logical OR of the update history information in which the area positions of the copy source logical disk have one to one correspondence to bit positions and the forcible copy position information is calculated so that the copy target information is created, and areas to be copied are managed based on the created copy target informatio
Fujitsu Limited
Greer Burns & Crain Ltd.
Kim Matthew
Li Zhuo H.
LandOfFree
Method and apparatus for inter-disk copy processing, and a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for inter-disk copy processing, and a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for inter-disk copy processing, and a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3154698