• Journal of the Institute of Convergence Signal Processing
• /
• v.10 no.4
• /
• pp.280-288
• /
• 2009

In this paper, we developed new time information recording module of VSI (VLBI Standard Interface) format by analyzing the Mark5B recorder control and operation software with 1Gbps speed, which is able to record the weak signal of space radio source, through the Korean VLBI Network (KVN). The control and operation software of high-speed recorder consists of 2 kinds of software, which is that it can operate RAID control board by controlling large capacity HDD drive and the network control and operation. Especially, core software in high-speed recorder is able to output the results after performing and analyzing the input command. Through the analysis of control and operation software, new time information recording module, which is needed to process the observed data for correlation, is developed. New developed time information recording module can record the time information together after checking the interrupt of 1PPS(Pulse Per Second) input signal when the observed data will be recorded. To verify the normal operation of the developed time information recording module, we performed the real observation test and confirmed the effectiveness of developed software through analyzing the recorded observation data.

• Journal of KIISE:Computing Practices and Letters
• /
• v.14 no.5
• /
• pp.537-541
• /
• 2008

Log-Structured File System(LFS) is a disk based file system that is optimized for improving the write performance. LFS gathers dirty data in memory as long as possible, and flushes all dirty data sequentially at once. In a real system, however, maintaining dirty data in memory should be flushed into a disk to meet file system consistency issues even if more memory is still available. This synchronizations increase the cleaner overhead of LFS and make LFS to write down more metadata into a disk. In this paper, by adapting Non-volatile RAM(NV-RAM) we modifies LFS and virtual memory subsystem to guarantee that LFS could gather enough dirty data in the memory and reduce small disk writes. By doing so, we improves the performance of LFS by around 2.5 times than the original LFS.

• Proceedings of the IEEK Conference
• /
• 1998.10a
• /
• pp.775-778
• /
• 1998

근래에 들어 컴퓨터 기술은 멀티미디어 기수의 발달과 더불어 그에 따른 데이터량의 증가로 인해 데이터를 처리, 전송, 저장하는 모든 부문에서의 고속, 대용량화를 요구하고 있다. 이 중에서 특히 저장장치 부문은 응용 프로그램이 대형화되고 멀티미디어화에 따른 데이터량이 크게 증가하는 추세에 있기 때문에 지속적인 용량 증가가 요구되고 있다. 이런 상황에서 주목을 받고 있는 것이 신호처리 방식을 개선하여 저장장치의 기록 밀도를 향상시키는 기술의 하나인 partial response maximum likelihood (PRML) 기술이다. PRML 방식은 HDD 나 광 디스크로부터 데이터를 읽어낼때의 신호처리 기술 중의 ㅎ나로 신호간 간섭을 허용하여 데이터 속도를 증가시키고, 신호를 재생할 때 신호간 간섭을 보상하여 원래 신호를 복원해 내는 기술이다. 이를 이용하면 기존의 기록방식에 비해 기록밀도를 20-50% 정도 높일 수 있다.〔1〕〔2〕

• Proceedings of the Korean Information Science Society Conference
• /
• 2005.11b
• /
• pp.172-174
• /
• 2005

플래시 메모리는 오늘날 다양한 형태로 우리 생활의 일부를 차지하고 있다. 휴대 전화기, MP3 플레이에, PDA등과 같은 모바일제품, 이동식 저장매체, 유비쿼터스 컴퓨팅 환경 등에 광범위하게 활용되고 있다. 이처럼 많은 분야에서 사용되는 주된 이유는 플래시 메모리의 장점인 저전력 비휘발성, 고성능, 물리적 안정성, 휴대성을 갖기 때문이다. 더불어 최근에는 Gb급 플래시 메모리도 개발되어 하드디스크의 자리를 대체할 수 있는 상황에 이르렀다. 하지만, 플래시 메모리는 하드디스크와 달리 이미 데이터가 기록된 블록에 대해 덮어쓰기(overwrite)가 되지 않는다는 특성을 갖고 있다. 덮어쓰기 위해서는 해당 블록을 지우고(즉, 소거(erase)) 쓰기 작업을 수행해야 한다. 이로 인해 플래시 메모리의 데이터 읽기/쓰기/소거에 비용이 하드 디스크와 같이 동일한 것이 아니라 서로 다르다(읽기 비용을 1로 가정할 경우 쓰기와 소거는 각각 8, 65)[1][5][6]. 따라서 OS, DBMS 등과 같은 시스템 소프트웨어에서 사용된 기존 버퍼 교체 기법은 플래시 메모리의 특성이 고려되지 않았기 때문에 플래시 메모리의 특성을 고려한 효율적인 버퍼 교체기법이 필요하다. 본 논문에서는 플래시 메모리의 서로 다른 연산 비용 고려한 새로운 버퍼 교체 기법을 제안한다.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.47 no.12
• /
• pp.24-30
• /
• 2010

The super-resolution near-field structure (super-RENS) disc system is the most promising one for next-generation optical data storage systems to succeed the Blu-ray disc (BD). In this paper, we apply the simplicial canonical piecewise-linear (SCPWL) model to modeling super-RENS read-out signals since reliable and accurate channel modeling is essential for performance analysis and development of equalizers for super-RENS systems. The validity of this model is verified using radio frequency (RF) signal samples obtained from a super-RENS disc, The experiment results on modeling indicate that the SCPWL model can be efficiently utilized for the nonlinear modeling of the super-RENS systems.

• Journal of KIISE:Computing Practices and Letters
• /
• v.15 no.9
• /
• pp.685-689
• /
• 2009

Flash memory has several features such as low~power consumption and fast access so that there has been various research on using flash memory as new storage. Especially the Solid State Disk which is composed of flash memory chips has recently replaced the hard disk. At present, SSD adopts the multi-channel and multi-way architecture to exploit advantages of parallel access. In this architecture, data are written on SSD in a unit of a superblock which is composed of multiple blocks in which some blocks are put together. This paper proposes two schemes of selecting, segmenting and re-composing victim superblocks to optimize concurrent processing when a buffer flush occurs. The experimental results show that 35% of superblock- based write operations is reduced by selecting victims and additional 9% by composition of superblock.

• Journal of the Korean Magnetics Society
• /
• v.6 no.3
• /
• pp.174-178
• /
• 1996

A method was studied which simulate signal and noise for magneto-optical disk drive system Recorded mark patterns and incident laser beam were modeled and discretized. Using them readout waveformj and amplitude were simulated. Adding Gaussian random noise to the readout signal and executing one dimensional discrete FFT (Fast Fourier Transform) algorithm signal and noise spectrum was estimated. From the spectrum, CNR (Carrier to Noise Ratio) was obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.837-842
• /
• 2007

Information storage devices using disks have a disk vibration at the frequency which is equivalent to the disk rotational speed. They also have a track vibration due to the disk eccentricity at the same frequency. In near field recording systems, the former affects the air-gap servo and the latter affects the tracking servo. In this paper, we introduce a novel control algorithm based on the internal model principle to both servos. A controller block designed by the principle is connected to the base lead-lag type compensator in parallel in order to cancel the repeatable run-out due to the disk vibration or eccentricity. Simulation and practical application of the algorithm on a near field recording system show good servo performance.

• Proceedings of the IEEK Conference
• /
• 2003.11b
• /
• pp.215-218
• /
• 2003

본 논문에서는 한국우주전파관측망(Korean VLBI Network; KVN)을 위해 현재 미국 MIT Haystack 천문대에서 개발되고 있는 천문관측 데이터를 위한 고속 대용량 저장장치에 대해 간략히 기술한다. 현재 개발중인 Mark 5 시스템은 하드디스크 기반의 Gbps VLBI 데이터 시스템이다. 주요 시스템은 낮은 가격의 PC 기반으로 8개의 탈부착이 가능한 ATA/IDE 형태의 하드디스크 뱅크를 두 개 가지며 1024Mbps 이상으로 고속기록 및 재생이 가능하다. 뿐만 아니라, Mark 5 시스템은 표준 기가비트 이더넷 연결을 통해 e-VLBI를 지원한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.984-985
• /
• 2014

This research investigates to analyze the effect of laser of thermally assisted magnetic recording system on diamond like carbon (DLC) layer of slider. We investigated a damaged DLC layer of slider with laser spot-induced damage and analyze the effect of the damaged DLC layer in slider dynamics. The damaged DLC layer resulted in change of flying height and air bearing stiffness pressure.