Electronics and Telecommunications Research Institute

Yu Hyeon Bak

Young Ho Kim

Chang Soo Kim

Bum Joo Shin

Dong Jae Kang

Myung Joon Kim

An efficient snapshot technique based on a mapping for a large logical volume shared in multiple hosts. According to the present invention, problems of time delays in a conventional snapshot technique is solved by employing a FAB and an SSB, which are bits representing whether a COW operation is carried out to a mapping entry. In other words, the present invention solves the problems of delaying a write operation of corresponding volume, which is simultaneously executed when a snapshot is created, until the snapshot creation is completed.

System and method of an efficient snapshot for shared large storage

Disclosed is a coherence preservation method of duplicated data in RAID subsystem. The method comprises the steps of: if a read operation is requested by the RAID subsystem, selecting an arbitrary target disk among disks having duplicated data, and implementing the read operation on the selected disk; implementing a read error handling to determine whether an error occurs in the disks selected upon the read operation, and if the error occurs in the read operation of the selected target disk, repeating the read error handling until the read operation of the data succeeds by circulating the remaining metering-treated disks in turns; after the read error handling, if the read operation on the remaining disk in all succeeds, completing the read error handling, and if the read operation on the remaining disk in all fails, returning the error to the disk, and completing the read error handling; if a write operation is requested by the RAID subsystem, implementing the write operation on the disks having duplicated data; after implementing the write operation, if a temporary error occurs in the duplicated data, implementing a temporary error handling to maintain the data coherence in the disks having the duplicated data and to recover the temporary error; and after implementing the write operation, if a permanent error occurs in the duplicated data, implementing a permanent error handling to maintain the data coherence in the disks having the duplicated data and to recover the permanent error.

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Taejon, South Korea

Yu Hyeon Bak