• Journal of Industrial Technology
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• v.15
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• pp.103-111
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• 1995

In this paper we evaluate the performance of the cached RAID5 which uses the parity cache and the data cache to overcome the small write problem. From the result of the simulation study we show that the cached RAID5 provides performance improvement with reasonable cache size.

• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.752-759
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• 2010

In this paper, we propose differential-logging method to improve the performance of RMW(Read Modify Write) operations of DDR-SSD based software RAID. Small writes that are frequently occurred in enterprise applications are main factor to degrade the performance of RAID5. Once a block is updated in RAID5, the parity block of the block must be updated to maintain consistency of parity. Therefore, to process a small write request, we need to read its parity block stored in disk, read old data, perform XOR operation, and write updated data and parity block. Several methods for hard disk based software RAID are proposed to solve the small write problems in RAID 5. Ln this paper, we propose a differential-logging method which carefully considers the DDR-SSD to solve the small write problem in RAID 5. We show that our proposed method out performs the existing software RAID in LINUX through simulations.

• Journal of the Korea Society of Computer and Information
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• v.24 no.6
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• pp.1-9
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• 2019

Hard disks, which have long been used as secondary storage in computing systems, are increasingly being replaced by solid state drives (SSDs), due to their relatively fast data input / output speeds and small, light weight. SSDs that use NAND flash memory as a storage medium are significantly different from hard disks in terms of physical operation and internal operation. In particular, there is a feature that data overwrite can not be performed, which causes erase operation before writing. In order to solve this problem, a hot data for frequently updating a data for a specific page is distinguished from a cold data for a relatively non-hot data. Hot data identification helps to improve overall performance by identifying and managing hot data separately. Among the various hot data identification methods known so far, there is a technique of recording consecutive write requests by using a Bloom filter and judging the values by hot data. However, the Bloom filter technique has a problem that a new bit array must be generated every time a set of items is changed. In addition, since it is judged based on a continuous write request, it is possible to make a wrong judgment. In this paper, we propose a method using a counting filter for accurate hot data verification. The proposed method examines consecutive write requests. It also records the number of times consecutive write requests occur. The proposed method enables more accurate hot data verification.

• Journal of the Semiconductor & Display Technology
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• v.21 no.3
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• pp.1-6
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• 2022

Modern computer systems usually have special hardware for operations used in deep learning workload even edge computing environment. Non-volatile memories (NVMs) have been considered for alternative memory storage because they consume little static energy and occupy small area. However, there is a problem for NVMs to be directly adopted. An NVM cell has limited write endurance, so that the lifetime of NVM-based memory system is much shorter than that of conventional memory system. To overcome this problem for the deep learning system, this paper proposes a novel method to extend the lifetime based on the analysis of the deep learning workloads. If an incoming block has more than a predefined number of frequently used values, the cacheline is defined as write friendly block. During the victim selection, the cacheline has lower possibility to be chosen as victim. The experimental results show that the lifetime is increased by about 50% and energy consumption is decreased by 3% with a little performance hurt.

• The KIPS Transactions:PartA
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• v.10A no.2
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• pp.83-92
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• 2003

RAID 5 is a widely-used technique used to construct disk systems of high reliability and performance. This paper proposes APGOC (Adaptive Parity Group On Cache) organization on cache to solve "small write" problem of RAID 5 especially in OLTP (On-Line Transaction Processing System) environments. In our approach, when user process makes a request for a file to kernel, the information on the read/write characteristics is added to the file data structure of the file system. With this information, data and parity cache can be managed interchangeably through parity fetching. Therefore we can enhance the cache utilization and improve the disk request response time. Our method is analyzed and evaluated with a simulation method. Comparing with previous works, we observed about 6~l3% of performance enhancement.hancement.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.12-14
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• 1998

본 논문은 RAID5가 갖는 쓰기 문제를 극복하기 위하여 지금까지의 연구 중에서 가장 우수한 성능을 나타내는 패리티 로깅 기법의 단점을 개선한 새로운 패리티 로깅 기법을 제안한다. 제안된 기법은 패리티 로깅기법에서 가장 큰 오버헤드인 패리티 로그의 크기를 줄이기 위하여 로그 데이터를 압축하는 방법을 사용한다. 로그 데이터의 압축은 로그 데이터의 저장에 필요한 비휘발성 버퍼의 크기와 로그 데이터 접근시간을 감소시켜 전체적인 성능을 향상시킬수 있다. 시뮬레이션을 통한 성능분석 결과에서 제안된 기법은 기존의 패리티 로깅 기법에 비하여 디스크 접근시간에서 우수한 성능을 나타냄을 보인다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.2
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• pp.302-312
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• 2012

In this paper, small-area and high-reliability design techniques of a 512-bit EEPROM are designed for UHF RFID tag chips. For a small-area technique, there are a WL driver circuit simplifying its decoding logic and a VREF generator using a resistor divider instead of a BGR. The layout size of the designed 512-bit EEPROM IP with MagnaChip's $0.18{\mu}m$ EEPROM is $59.465{\mu}m{\times}366.76{\mu}m$ which is 16.7% smaller than the conventional counterpart. Also, we solve a problem of breaking 5V devices by keeping VDDP voltage constant since a boosted output from a DC-DC converter is made discharge to the common ground VSS instead of VDDP (=3.15V) in getting out of the write mode.

• The Transactions of the Korea Information Processing Society
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• v.4 no.11
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• pp.2849-2860
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• 1997

In this paper, we present efficient cache replacement policies for the software RAID file system. The performance of this policies is compared to two other policies previously proposed for conventional file systems and adapted for the software RAID file system. As in hardware RAID systems, we found small-writes to be the performance bottleneck in software RAID file systems. To tackle this small-write problem, we propose cache replacement policies. Using trace driven simulations we show that the proposed policies improve performance in the aspect of the average response time and the average system busy time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.7
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• pp.1599-1606
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• 1997

The software RAID file system is defined as the system which distributes data redundantly across an aray of disks attached to each workstations connected on a high-speed network. This provides high throughput as well as higher availability. In this paper, we present an efficient caching scheme for the software RAID filte system. The performance of this schmem is compared to two other schemes previously proposed for convnetional file systems and adapted for the software RAID file system. As in hardware RAID systems, small-writes to be the performance bottleneck in softwre RAID filte systems. To tackle this problem, we logically divide the cache into two levels. By keeping old data and parity val7ues in the second-level cache we were able to eliminate much of the extra disk reads and writes necessary for write-back of dirty blocks. Using track driven simulations we show that the proposed scheme improves performance for both the average response time and the average system busy time.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.2
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• pp.269-275
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• 2008

The rapid growth of ubiquitous technology has increased the demand of storage capacity in mobile computing. iSCSI(Internet Small Computer Interface), a virtual storage protocol would be one of the possible solutions to resolve this problem. However, the insecure nature of this protocol makes it vulnerable to malicious attacks. In this paper, we aims to design and propose a new secure lightweight iSCSI-based virtual storage scheme for mobile devices. Suitable security mechanisms are considered in the design of our proposed solution in order to overcome existing security problems in iSCSI. Relevant experiments are tarried out and the results revealed that the efficiency of proposed algorithm in which it introduces over 100% Read/Write performance improvement compared with the IPsec approach.