Hongchan Roh

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Previous research addressed the potential problems of the harddisk oriented design of DBMSs of flashSSDs. In this paper, we focus on exploiting potential benefits of flashSSDs. First, we examine the internal parallelism issues of flashSSDs by conducting benchmarks to various flashSSDs. Then, we suggest algorithm-design principles in order to best benefit(More)
Flash memory has critical drawbacks such as long latency of its write operation and a short life cycle. In order to overcome these limitations, the number of write operations to flash memory devices needs to be minimized. The B-Tree index structure, which is a popular hard disk based index structure, requires an excessive number of write operations when(More)
Flash-based Solid State Storage (flashSSS) has write-oriented problems such as low write throughput, and limited life-time. Especially, flashSSDs have a characteristic vulnerable to random-writes, due to its control logic utilizing parallelism between the flash memory chips. In this paper, we present a write-optimized layer of DBMSs to address the(More)
Biclustering is a popular method which can reveal unknown genetic pathways. However, even though many algorithms have been suggested, no overwhelming algorithm has been suggested, due to its significant search space, until now. In this respect, several evolutionary algorithms tried to address this problem utilizing the powerful search capability of(More)
Recently, flash memory has been utilized as the primary storage device in mobile devices. SSDs have been gaining popularity as the primary storage device in laptop and desktop computers and even in enterprise-level server machines. SSDs have an array of NAND flash memory packages and are therefore able to achieve concurrent parallel access to one or more(More)
Personal information that is collected online can be misused and abused. Therefore, data security techniques that restrict the usage of data only to purposes specified by data providers are needed. The LDHD model, a well-known database security model, expresses the purpose of data provision in the unit of cell in order to have a detailed control over(More)
An inverted index is a core data structure of Information Retrieval systems, especially in search engines. Since the search environments have become more dynamic, many on-line index maintenance strategies have been proposed. Previous strategies were designed for HDDs. Consequently, in order to avoid expensive random access cost, Merge-based strategies have(More)
The use of flashSSDs has increased rapidly in a wide range of areas due to their superior energy efficiency, shorter access time, and higher bandwidth when compared to HDDs. The internal parallelism created by multiple flash memory packages embedded in a flashSSDs, is one of the unique features of flashSSDs. Many new DBMS technologies have been developed(More)