• Journal of KIISE:Databases
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• v.31 no.2
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• pp.108-121
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• 2004

In this paper, we propose an enhanced snapshot technique that solves performance degradation when snapshot is initiated for the storage cluster system. However, traditional snapshot technique has some limits adapted to large amount storage shared by multi-hosts in the following aspects. As volume size grows, (1) it deteriorates crucially the performance of write operations due to additional disk access to verify COW is performed. (2) Also it increases excessively the blocking time of write operation performed during the snapshot creation time. (3)Finally, it deteriorates the performance of write operations due to additional disk I/O for mapping block caused by the verification of COW. In this paper, we propose an efficient snapshot technique for large amount storage shared by multi-hosts in SAN Environments. We eliminate the blocking time of write operation caused by freezing while a snapshot creation is performing. Also to improve the performance of write operation when snapshot is taken, we introduce First Allocation Bit(FAB) and Snapshot Status Bit(SSB). It improves performance of write operation by reducing an additional disk access to volume disk for getting snapshot mapping block. We design and implement an efficient snapshot technique, while the snapshot deletion time, improve performance by deallocation of COW data block using SSB of original mapping entry without snapshot mapping entry obtained mapping block read from the shared disk.

• Journal of Korea Multimedia Society
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• v.2 no.4
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• pp.459-467
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• 1999

With fully harnessing the functions provided by Windows NT, we suggest the generating method of RPL profile and the RPL protocol for remote booting on DL-NCS(Network Computing System for Diskless client PCs). This system can offer clients, without having hard disk, boot remotely Window 9x stored in server's hard disk and can share peripheral devices and application programs in the server side. For booting Window 9x from DL-NCS, twenty-five clients' PCs were set for simultaneous on and finally the PCs were booted in similar time interval compared to that from a desktop PC having local disk. This system was also experimented to the application programs. And this system can yield excellent networking environments. In sum, with using this DL-NCS, we can reduce the installing costs of peripheral device, recycle the lower grade PCs such as 486SX/DX, and save the budgets for software purchase.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4B
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• pp.323-338
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• 2003

The main memory database systems (MMDBMS) efficiently supports various database applications that require high performance since it employs main memory rather than disk as a primary storage. Recently, it has been increased needs that have the fast data processing as well as the efficient modeling of application requiring for a complicated structure, and conformity to applications that need the strict dta consistency. In MMDBMS, because all the data is located in the main memory, it can support the usable expression methods of data satisfying their needs without performance overhead. The method has the operation to manipulate the data and the constraint such as referential integrity in more detail. The data model consists of this methods is an essential component to decide the expression power of DBMS. In this paper, we discuss about various requests to provide the communication services and propose the data model that support it. The mainly discussed issues are 1) definition of the relationship between tables using the pointer, 2) navigation of the data using the relationship, 3) support of the referential integrity for pointer, 4) support of the uniform processing time for the join, 5) support of the object-oriented concepts, and 6) sharing of an index on multi-tables. We discuss the pointer-based data model that designed to include these issues to efficiently support complication environments.